Muscle fatigue measurement method

Abstract

The method for quantifying muscle fatigue includes electrically stimulating a muscle with charges at different frequencies, the charges being iteratively determined to generate reliable and accurate forces in the muscle in response to the electrical stimulation, and quantifying these forces and muscle fatigue based thereon.

Description

[Technical field]

[0001] The present disclosure relates to a method for quantifying muscle fatigue. [Background technology]

[0002] Animal activity, and in particular human activity, induces "fatigue". Such fatigue can be neurological (i.e. induced by intellectual or mental activity) and / or physical (i.e. induced by physical work). Physical fatigue is called "muscular fatigue" because it results from muscular work and leads to a decrease in the force that can be exerted by the affected muscles. In particular, muscular fatigue can result in the inability to maintain and / or repeat a physical load.

[0003] The identification, measurement and / or monitoring of muscle fatigue plays an important role, for example, in sports exercise (for the purposes of e.g. optimizing training efficiency, preventing injuries, devising personal sports training programs, muscle preparation, etc.) and in physical therapy for muscle rehabilitation (for the purposes of e.g. monitoring physical exertion, optimizing treatment, preventing overtreatment, etc.).

[0004] A known method for assessing such muscle fatigue of a subject is to perform a test that requires multiple repeated maximal voluntary contractions of said muscles (e.g., by voluntary movement). Muscle fatigue is considered to be identified when a predetermined maximal muscle force according to the monitored data (time, speed, force, power, acceleration, etc.) cannot be reached. The subject's motivation for such maximal contraction of the muscle may, however, affect such muscle fatigue assessment. This test also induces significant muscle fatigue, which in turn affects the results obtained by the method. In particular, the test cannot be repeated multiple times, and it cannot be performed after intense muscle work. The method further has the drawback of exposing the subject to the risk of injury.

[0005] In order to solve the above-mentioned problems, the now unpublished US Pat. No. 6,239,633 discloses a method for manufacturing a semiconductor device comprising the steps of: (i) electrically stimulating a muscle at different frequencies; (ii) quantifying the force exerted by the muscle in response to the electrical stimulation of step (i); (iii) quantifying muscle fatigue based on the forces quantified in step (ii). The present invention provides a method for quantifying muscle fatigue, comprising:

[0006] The method uses electrical stimulation in step (i) to involuntarily stimulate a muscle, whatever its fatigue and condition, without exposing the subject to the risk of injury. Muscle fatigue can then be easily quantified in step (iii) since muscle fatigue causes the force measured in step (ii) to vary non-uniformly with the frequency of electrical stimulation. The method is advantageous because it does not require any comparison with subject normative data, preliminary measurements, or specific performance conditions.

[0007] The muscle fatigue quantified from step (iii) may, however, be compromised by errors resulting from the quantification of force in step (ii). For example, in the case of force quantification by a measuring instrument, the smaller the force measured, the larger the measurement error. This may typically be due to the sensitivity limit of the instrument. Furthermore, the same electrical stimulation in the same conditions of the same muscle in two different subjects may lead to two very different force quantifications as a function of the muscle itself. For example, older subjects, high body index, or changes in any muscle (e.g., atrophy) may reduce the force quantified in step (ii). In some cases, these factors may affect the force quantified in step (ii) such that these forces are smaller in comparison to the errors resulting from the quantification technique (e.g., the sensitivity of the measuring instrument), resulting in an inaccurate quantification of muscle fatigue.

[0008] It would be desirable to provide a more accurate and reliable method for quantifying muscle fatigue. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Application Serial No. 17 / 091,468 Summary of the Invention [Means for solving the problem]

[0010] It is an object of the disclosed subject matter to provide a reliable and more accurate method for quantifying muscle fatigue. To this end, the disclosed subject matter provides a method for quantifying muscle fatigue in a muscle, comprising the following steps in the following order: (a) setting target numerical ranges for electric charge and muscle force; (b) electrically stimulating the muscle with isolated pulses of said charge; (c) quantifying the force exerted by the muscle in response to the electrical stimulation of step (b); (d) if the force determined in step (c) does not fall within the target range of muscle strength, (d.1) comparing the force determined in step (c) with a target numerical range of muscle strength; (d.2) modifying the charge in response to the comparison of substep (d.1); and (d.3) repeating steps (b) to (d); (i) electrically stimulating a muscle with said charges at different frequencies; (ii) quantifying the force exerted by the muscle in response to the electrical stimulation of step (i); (iii) quantifying muscle fatigue based on the forces quantified in step (ii). The present invention provides a method comprising:

[0011] The method according to the present disclosure is more reliable and more accurate in quantifying muscle fatigue than the method described in US Pat. No. 5,399,633, while reproducing all of its advantages.

[0012] In fact, steps (i) to (iii) of this method are part of the method of the disclosed subject matter, following the quantification of muscle fatigue in step (iii). In particular, the method is therefore efficient, safe and highly adaptable for quantifying muscle fatigue, due to the use of electrical stimulation in step (i), which allows stimulating the muscle no matter how tired it is, and making the muscle involuntarily exert force in response to the electrical stimulation. This step can be performed at any time, even after sports practice, without exposing the subject to the risk of injury. It does not depend on the subject's will to maximally contract the muscle. Step (i) also does not induce significant muscle fatigue, since the number of electrical stimulations is preferably limited and performed in a short time, in order to observe the muscle's response and to quantify the force in step (ii). The quantification of muscle fatigue in step (iii) is efficient, since it benefits from the fact that muscle fatigue non-uniformly deforms the curve graph of the force exerted by the muscle in response to electrical stimulation at a certain frequency as a function of this frequency. Therefore, it is easily possible to quantify muscle fatigue in step (iii) based on at least two points on this curve graph. Such quantification of muscle fatigue does not depend on the circumstances of the execution of the method. It does not require comparison with such a standard curve graph at rest for the subject, nor preliminary measurements, nor restrictive execution conditions.

[0013] The reliable and accurate features of the method result from the consideration of a novel parameter, the charge.

[0014] Each electrical stimulus of step (i) includes a repetition of a pulse at one of the frequencies. The "charge" is typically defined by the electrical intensity of the pulse, and / or by the individual pulse duration (or pulse width), and / or by the voltage of the pulse at a fixed current. In this document, the charge preferably corresponds to the electrical intensity of the pulse, so that any modification of the charge of the pulse (as below) preferably corresponds only to a modification of the electrical intensity of the pulse. This preferred embodiment does not exclude from the scope of the disclosed subject matter another type of "charge" as it may be understood from the inclusiveness of the term "charge". In particular, the modification of the charge may also be made by modifying one or more pulse parameters of electrical intensity, voltage or width at a fixed current.

[0015] As specified in step (i), the electrical stimulation is generated with a specific charge resulting from novel steps (a)-(d) of the method, in which the charge is initially used as an iteration parameter in steps (b)-(d). The charge set in step (a) consists for example of a common or intermediate charge (e.g. electrical strength of the pulse of 15, 20 or 25 mA). It is mainly used to initialize the iteration. The iterations guided by steps (b)-(d) aim to determine an appropriate pulse charge for carrying out steps (i)-(iii) while avoiding the drawbacks of the prior art.

[0016] More specifically, the suitability of using the charge set in step (a) to electrically stimulate the muscle in step (i) is tested through a single isolated pulse in step (b). This pulse is used to observe the muscle's response in order to quantify the force exerted by the muscle in step (c). This force is then evaluated whether it is sufficient to carry out steps (i)-(iii) in the sense that it is not too low and / or too high in view of the muscle's properties (e.g. the subject's age, body mass index, and / or muscle variability) and / or the force quantification technique used (e.g. the sensitivity of the measuring device used in step (ii)).

[0017] This assessment is performed in the disclosed subject matter very simply by setting a target numerical range for muscle forces in step (a). The setting of a target numerical range for muscle forces in step (a) aims to define a range of acceptable (strictly positive) forces that can be obtained in step (b) in view of the implementation of steps (i)-(iii) and depends on the muscle (and thus on the subject) and / or on the system used to implement the method (e.g. on the sensitivity of the measuring equipment). This numerical range is therefore typically at least half-limited, i.e. limited only by a lower limit, only by an upper limit, or both.

[0018] Preferably, the target numerical range of muscle forces has (at least) a lower limit, which typically corresponds to the minimum acceptable force to be highly reliable given the sensitivity of the quantification techniques used in steps (c) and (ii). In addition, advantageously, this lower limit is high enough to accommodate minor potential disturbances that may be encountered during the performance of steps (c) and (ii), such as voluntary contractions or external vibrations, so that errors in the forces quantified in those steps are minimized.

[0019] Nevertheless, these forces should not be so strong that they make the execution of the method uncomfortable for the subject. In particular, a lower limit should be established high enough to make the force determination reliable and low enough to keep the execution of the method comfortable enough for the subject. For example, such a lower limit may be 3N, 4N, 5N, 6N, 7N, 8N, 9N, or 10N, depending on the muscle and the force determination technique. For example, if a lower limit of 8N may be favorable for the quadriceps muscle of an intermediate subject (without changes in age, in body mass index, and in muscle), a lower limit of 4N may be better for the biceps muscle of the same subject. In any case, this lower limit depends on the determination technique used to quantify the force in steps (c) and (ii). The adjusted lower limit is preferably at least 5N, and more preferably approximately 5N. The lower limit is more generally comprised between 2 and 10N.

[0020] In order to keep the performance of the method comfortable for the subject, the target numerical range of muscle strength may have an upper limit. For example, the upper limit may be 50N, 60N, 70N, 80N, 90N, or 100N, depending on the muscle (and therefore the subject) and / or the force quantification technique, as for the lower limit. The target numerical range of muscle strength preferably has a lower limit, but such numerical ranges with a single upper limit as described are not excluded from the scope of the disclosed subject matter.

[0021] The data of the target numerical range of the muscle force is equivalent to the data of its lower and / or upper limit, if present, so that setting this numerical range in step (a) can be paraphrased as setting such limit values, and checking in step (d) whether the force quantified in step (c) belongs to the numerical range can be paraphrased as checking whether this force is smaller than (or equal to) the upper limit, if present, and larger than (or equal to) the lower limit, if present. The numerical range can be half-open, half-closed, open or closed, and / or bounded or half-bounded, with respect to the usual topology with real numbers. As will be understood, the above term "or equal to" applies to numerical ranges bounded by the considered limit values.

[0022] Step (d) of the method provides for the repetition of the charge. In particular, if the charge used to electrically stimulate the muscle in step (b) results in a force that is included in the target numerical range of muscle force, i.e. the charge is reliable in terms of the system used to implement the method (e.g. in terms of the sensitivity of the force measuring device) and in terms of the subject, it can be maintained for the subsequent execution of steps (i) to (iii). If not, the charge is modified in sub-step (d.2) by comparison in sub-step (d.1) between the force determined in step (b) and the target numerical range of muscle force set in step (a). An example of such a comparison is presented hereafter.

[0023] The correction by the charge step aims to correct the unreliability of the force determination and thus to improve the determination of muscle fatigue in step (iii). This corrected charge step is then the charge step used for a new execution of steps (b) to (d), as derived in sub-step (d.3). Steps (b) to (d) therefore advantageously allow an iterative determination of the charge used in steps (i) to (iii) in order to progressively reduce the unreliability in the force determination, which improves the accuracy and reliability of the muscle fatigue determination method originally defined from steps (i) to (iii). In particular, the "charge" used when performing step (i) for the first time is the charge set in step (a) or the charge corrected when performing step (d.2) for the last time, by iteration.

[0024] Typically, the charge used when first performing step (i) is comprised between 25 and 40 mA, and the charge initially set in step (a) is generally comprised between 15 and 30 mA. It may therefore be preferable to set a charge of 25 mA in step (a). These data are not intended to limit the scope of the disclosed subject matter. In particular, the charge set in step (a) is more generally comprised between 10 and 40 mA.

[0025] As mentioned above, steps (c) and (ii) are preferably performed by an instrument arranged to measure the forces quantified in steps (c) and (ii), in which case the target numerical ranges for the charge and / or muscle force set in step (a) depend on the muscle and / or on at least one technical characteristic of the instrument.

[0026] In particular, it is advantageous to adjust the charge via steps (b)-(d) before step (i). Indeed, if the charge is adjusted during the electrical stimulation of step (i), it may affect the quantification of muscle fatigue by generating electrical fatigue and / or enhancement (as will be explained hereinafter), providing unnecessary electrical shocks and being uncomfortable for the subject.

[0027] As explained above, the charge is preferably defined by the electrical intensity of the pulses constituting the electrical stimulation (of steps (b) and (i)), such that a modification of the charge in substep (d.2) corresponds to a modification of the electrical intensity. The electrical intensity has the advantage that it is easy to modify and to monitor during the execution of the method. The electrical intensity, or more generally the charge, corresponds to the quality of the motor units or muscle fibres to which the method is applied, which consequently affects the response of the muscle to the electrical stimulation.

[0028] A preferred embodiment of substeps (d.1) and (d.2) for correcting the charge before the first execution of step (i) is described below. In this embodiment, the comparison of substep (d.1) comprises the determination of the ratio of the reference force of the target numerical range of muscle forces to the force determined in step (c). This ratio is easy to calculate and gives accurate information on the percentage difference between the force determined in step (c) and the reference force and thus the numerical range. In some cases, this reference force data can be equivalent to the numerical range data. For example, this is the case when the reference force is always selected as the middle of a bounded numerical range or as the lower limit of a half-bounded numerical range.

[0029] The reference force is preferably the lower or upper limit of a target numerical range of muscle force. If the reference force corresponds to the lower (upper) limit of the numerical range, and if the force quantified in step (c) is less (greater) than the lower (upper) limit, the ratio indicates the proportion to apply to the charge in sub-step (d.2) to result in a force within the numerical range the next time step (c) is performed.

[0030] With respect to the charge corresponding to the electrical intensity of the pulse, the inventors have discovered that if the force exerted by a muscle in response to electrical stimulation of the muscle with an isolated pulse at a certain charge varies predominantly linearly with respect to the charge, then this ratio corresponds exactly to the correction to apply to the charge. This linearity was derived from a statistical regression with a high correlation index. Therefore, the correction of the charge is preferably determined in sub-step (d.2) by the formula E'F=EF', where: E is the charge, E' is the corrected charge to be determined, F is the force determined in step (c), ·F' is the reference force.

[0031] As may be noted, the ratio calculation of substep (d.1) is implicit from this formula, which has the main advantage that it makes it possible to obtain a suitable charge to carry out steps (i) to (iii) by carrying out steps (b) and (c) twice (or at most three times), thereby making the method efficient in the case of a charge corresponding to the electrical strength.

[0032] This formula can also be generalized with respect to other "charges", since the ratio of substep (d.1) still at least indicates the correction of substep (d.2) as explained above. In an alternative approach, other functions more complex than such a linear function, whose coefficients are defined by the ratio of substep (d.1), can also be used to define the correction of the charge in substep (d.2). However, such functions can make the method more difficult and slow to execute.

[0033] A numerical example is now presented. If the charge set in step (a) is 15 mA, the force quantified in step (c) is 3 N, and the target numerical range of the muscle force is a closed half-limited numerical range [5N, +∞[, taking the lower limit as 5N as the reference force, the ratio of sub-step (d.1) is 5 / 3 and the corrected charge is 25 mA. By testing this charge through a new execution of steps (b) and (c), as guided by sub-step (d.3), the force newly quantified in step (c) will be close to 5N. Since the reference force is selected as the limit value of the numerical range, taking into account errors due to the sensitivity of the force quantification technique or other disturbances, the force quantified when performing step (c) this second time may still be smaller than 5N and therefore outside the numerical range. In this case, a third execution of steps (b) and (c) is guided by step (d). For example, if this new force is 4.5 N, then the 10 / 9 ratio from sub-step (d.1) is applied to the current charge of 25 mA. The corrected charge is then 28 mA (rounded to the unit). Performing steps (b) and (c) a third time is then performed, further resulting in a final force of 5.5 N in step (c). If this force belongs to the numerical range, step (d) is not performed any further and step (i) can be performed with this charge.

[0034] As can be deduced from this example, it may be more advantageous to use a reference force close to the lower limit without exactly corresponding to this lower limit, in order to avoid performing steps (b) and (c) this third time. Indeed, if the reference force is selected as 6N, the corrected charge will be 30mA and the force determined when performing step (c) the second time will certainly be just greater than 5N. Therefore, more generally, the reference force is preferably selected from the lower or upper limit of a numerical range, a lower limit increased by a force step, or an upper limit decreased by a force step. Preferentially, such a "force step" is included between 1 and 5N, for example it is 1N, 2N, 3N, 4N or 5N.

[0035] Alternatively to the preferred embodiment detailed above, other implementations of substeps (d.1) and (d.2) are entirely part of the scope of the disclosed subject matter. As an example of such other implementations, substep (d.1) may include determining whether the force determined in step (c) is greater or smaller than all forces included in the target numerical range of muscle forces, and substep (d.2) may consist in decreasing or increasing the charge by a predetermined step (e.g., 0.5, 1, 2, 3, 4 or 5 mA) in each of these cases, respectively. Considering the numerical example above with such a step of 1 mA, if the value 3N is smaller than all forces in the numerical range [5N, +∞[, the charge is increased by 1 mA, so that the corrected charge is 16 mA for the second execution of steps (b) and (c). In this case, the force determined when performing step (c) for the second time with this charge is not sufficient. The same applies for the third, fourth, etc. executions. Approximately 14 runs of steps (b) and (c) are thus required to reach a charge of 28 mA.

[0036] This alternative implementation of sub-steps (d.1) and (d.2) is very simple and systematic. It does not require any actual calculations. Nevertheless, it may take longer to perform.

[0037] In any case, step (d) defines an iteration of steps (b) to (d), and the modification of the charge in sub-step (d.2) is typically performed iteratively.

[0038] The methods according to the present disclosure are convenient for a wide range of applications, in particular for quantifying muscle fatigue in professional athletes before, during or even after practice or competition, as well as in injured and / or elderly individuals during muscle rehabilitation.

[0039] The quantification method according to the present disclosure is particularly useful for planning sports training. The method according to the present disclosure is generally not intended to be applied for therapeutic purposes and is not intended to identify or elucidate pathologies. In this regard, an embodiment of the disclosed subject matter can be read as follows: 1. A method for planning a sporting activity, comprising the steps of: (a) setting target numerical ranges for electric charge and muscle force; (b) electrically stimulating the muscle with isolated pulses of said charge; (c) quantifying the force exerted by the muscle in response to the electrical stimulation of step (b); (d) if the force determined in step (c) does not fall within the target range of muscle strength, (d.1) comparing the force determined in step (c) with a target numerical range of muscle strength; (d.2) modifying the charge in response to the comparison of substep (d.1); and (d.3) repeating steps (b) to (d); (i) electrically stimulating a muscle with said charges at different frequencies; (ii) quantifying the force exerted by the muscle in response to the electrical stimulation of step (i); (iii) determining at least one muscle data information based on the forces determined in step (ii); (v) planning a sports activity based on the muscle data information; The method includes:

[0040] Preferably, all, any, some or at least one of the muscle data information quantified in step (iii) is used in step (v) for planning a sports activity.

[0041] Preferably, the sports activity is sports practice.Preferably, the muscle data information includes (or possibly consists of) muscle fatigue (data).

[0042] The method for planning a sports activity is non-therapeutic and / or non-medical and / or non-therapeutic. In particular, step (v) is not intended to provide a therapeutic diagnosis. Preferably, step (v) comprises (or possibly consists of) quantifying time data dependent on muscle data information.

[0043] If the muscle data information includes (or possibly consists of) muscle fatigue (data), the sports activity planning method comprises the following steps: (0) identifying muscles stimulated during a sports activity; (1) performing a method according to the present disclosure to quantify muscle fatigue (or at least one piece of muscle fatigue data information) of the muscle identified in step (0); and (2) planning a sports activity based on the muscle fatigue (or at least one piece of muscle fatigue data information) determined in step (1); This can be rephrased as including.

[0044] In other words, step (1) corresponds to the above steps (a) to (iii). The muscle fatigue (data information) quantified in step (1) is preferably obtained from all, any, some or at least one of the muscle fatigue (data) quantified when performing the different step (iii), more preferably by calculating the average value of all of these muscle fatigue (data).

[0045] In general, the methods according to the present disclosure typically correspond to non-therapeutic and / or non-medical and / or non-therapeutic methods for quantifying muscle fatigue in a muscle, including steps (a)-(iii), in which case no therapeutic diagnosis is derived from step (iii).

[0046] Any of the preceding and following examples and advantages of the method according to the present disclosure, as generally described in the introduction of this disclosure, apply mutatis mutandis to the specific particulars of the above-disclosed methods, and in particular to the sports activity planning method and any non-therapeutic embodiments. In particular, any one of the embodiments presented in the claims may be considered alone or in combination with these methods.

[0047] Another general benefit of the quantification method of the present disclosure is that it allows to quantify specific muscle fatigue. In fact, muscle fatigue depends on many physiological factors. In particular, muscle fatigue can be caused by defects in the neuromuscular nervous control (leading to so-called "central muscle fatigue"), when the neuromuscular nervous control is no longer able to stimulate the muscle fibers to their maximum capacity, or by alterations in the contraction force at the direct level of the muscle fibers (leading to so-called "peripheral muscle fatigue"). Within the framework of the present disclosure, the quantification method allows to directly quantify peripheral muscle fatigue in step (iii) if the electrical stimulation of step (i) directly affects the peripheral muscle fibers, independent of the central nervous control of muscle contraction. The method can, however, also optionally include the quantification of central muscle fatigue, for example by subtracting the quantified peripheral muscle fatigue from a separate global fatigue measurement.

[0048] Moreover, peripheral muscle fatigue itself includes two types of muscle fatigue, depending on how long it affects the muscle: the so-called "short-lasting peripheral muscle fatigue", which is essentially related to energetic and / or metabolic factors, which can be quickly recovered from those factors (i.e., after a few minutes), and the so-called "long-lasting peripheral muscle fatigue", which lasts for hours and even days (e.g., after significant physical effort).

[0049] The muscle fatigue quantified in step (iii) is preferably long-lasting peripheral muscle fatigue. Optionally, short-lasting peripheral muscle fatigue can also be quantified by the method by carrying out the method of the present disclosure and performing additional quantification of muscle fatigue at a time interval and subtracting the obtained result.

[0050] Within the framework of the present disclosure, the term "electrical stimulation" and any of its variations preferably refers to electrical stimulation of the neuromuscular or any kind of stimulation of the motor neurons of the muscle to be tested. Such stimulation is preferably performed by a stimulator comprising a generator of electrical pulses and a device comprising electrodes adapted to be placed on the subject's skin in the vicinity and / or beside the muscle, and connected to the generator so that an electric current can be transmitted to the muscle by the electrodes. The device preferably comprises a control device for selecting the parameters of the electrical stimulation, such as the intensity and frequency of the electrical pulses. Such devices are known to those skilled in the art.

[0051] Within the framework of the present disclosure, each "force" quantified in step (ii) preferably corresponds to the maximum force exerted in response to a full pulse of electrical stimulation of step (i) at one of the frequencies. Similarly, each "force" quantified in step (c) preferably corresponds to the maximum force reached in response to an isolated pulse of electrical stimulation of step (b).

[0052] Within the framework of this document, the use of the indefinite article "a", "an" or the definite article "the" to present an element does not exclude the presence of a plurality of these elements. In this document, the terms "first", "second", "third" etc. are used only to distinguish elements and do not imply any order among these elements. In this document, the terms "at level of" and "at the level of" are used equivalently. Within the framework of this document, the terms "on basis of" and "on the basis of" are used equivalently. The latter is furthermore not limiting, and the fact that a first quantity is determined on the basis of a second quantity does not exclude that the first quantity is also determined on the basis of a third quantity together with the first quantity.

[0053] Within the framework of this document, the use of the verbs "comprise", "include", "involve" or any of their variations and conjugations does not exclude the presence of elements other than those stated. If the verb "comprise" is used to define a numerical range by the term "comprised between" these two values ​​should not be interpreted as being excluded from the numerical range.

[0054] Within the framework of this document, the use of the terms "preferred", "preferably", and "preferred" should not be considered limiting with respect to the scope of the disclosed subject matter or with respect to the interpretation of the claims. More specifically, the inclusion of a "preferred" range or embodiment in this disclosure is not intended to limit the scope of the claimed subject matter to include only the "preferred" embodiment. In this regard, the inclusion of a "preferred" embodiment should not be construed as expressing a disclaimer of subject matter not so specified.

[0055] In order to further improve the accuracy and reliability of the method of the presently disclosed subject matter, another preferred embodiment of the method, which is fully compatible with any of the previous embodiments, is presented below. According to this preferred embodiment, the method includes performing step (iv) several times after step (iii). Step (iv) includes the following sub-steps: (iv.1) increasing the charge by charge steps; (iv.4) Sub-step of repeating steps (i) to (iii) Includes.

[0056] This step (iv) therefore contemplates a further modification of the charge steps defined from steps (a)-(d), but after the first execution of step (i). This modification is performed by systematically adding a charge step to the current charge between two executions of step (i). For example, assuming the numerical example given above, and a number of executions of step (iv) of 10, this means that steps (i)-(iii) are performed a first time with a charge of 28 mA, then a second time with a charge of 29 mA, and so on up to an eleventh execution of steps (i)-(iii) with a charge of 38 mA.

[0057] Step (iv) makes it possible to improve the overall accuracy and reliability of the method, since it makes it possible to perform a comprehensive quantification (e.g. measurement) of the force in step (ii), and of the muscle fatigue in step (iii). This repetition of steps (i)-(iii) makes it possible, in particular, to calculate an average value of these data, and to ensure that the muscle fatigue is quantified accurately with a very small margin of error.

[0058] Nevertheless, the repetition of steps (i)-(iii) requires addressing a phenomenon in muscle physiology called "potentiation" (also known as post-activity potentiation, staircase phenomenon, or post-repetitive potentiation), as known and described in the scientific literature on muscle physiology.

[0059] This phenomenon is defined as the effect of a preceding muscle activity on the enhancement of a subsequent muscle contraction. Muscle activity leads to muscle fatigue and also to potentiation, which is the opposite phenomenon of peripheral muscle fatigue. Potentiation therefore occurs simultaneously with muscle fatigue and can somewhat compensate for it. This phenomenon of potentiation occurs with all kinds of muscle activity. Therefore, when performing electrical stimulation of the muscle in step (i) to quantify muscle fatigue, the electrically induced muscle contraction generates a potentiation of the muscle fibers that hides the muscle fatigue and disturbs its quantification. The disturbance of the quantification is even more significant because the electrical stimulation pulses are numerous and repeated within a certain time.

[0060] To mitigate or even avoid this enhancement, step (iv) contemplates not only repeating steps (i) to (iii), but also increasing the charge defined by steps (a) to (d) between two performances of step (i). Indeed, this increase in charge makes it possible to include new muscle fibers at each performance of step (i), which have not been enhanced by the preceding electrical stimulation. As a result, the spatial expansion of muscle fibers is modified at each performance of step (i), which is guided by step (iv).

[0061] Step (iv) therefore combines the advantages of both improving the accuracy of the method by repeating steps (i) to (iii) and of strongly mitigating muscle buildup, thereby effectively improving the accuracy of the method.

[0062] Preferably, each electrical stimulus of step (i) comprises a repetition of pulses with an electrical intensity comprised between 10 and 100 mA, and the increase in charge in sub-step (iv.1) consists of an increase in the electrical intensity of the pulses. In this case, the pulses increase from a lower to a higher value of electrical intensity, both between 10 and 100 mA. The lower value is iteratively determined by steps (a) to (d). It is typically comprised between 15 and 40 mA, more preferably it is about 25 mA to 30 mA, so that the subject feels a gentle first electrical stimulus in step (i). The higher value is preferably comprised between 30 and 60 mA, more preferably it is about 40 mA to 50 mA, so as to avoid too high a load on the muscle.

[0063] Preferably, the charge step, expressed in terms of electrical intensity, is comprised between +0.5 and +5 mA, more preferably it is about +1 mA, such step value being sufficient to electrically stimulate muscle fibres sufficiently different from those obtained by performing steps (i) to (iii) once relative to the others, and thus to mitigate the potentiation.

[0064] Preferably, the number of times performed is comprised between 5 and 30, more preferably between 10 and 20. For example, it may be about 15 times in order to perform a sufficient quantification (e.g., measurement) of force and muscle fatigue, and thus to make the margin of error from the method very small.

[0065] According to a non-limiting illustrative embodiment of step (iv), the charge defined from steps (a)-(d) is progressively increased by 15 charge steps of +1 mA throughout step (iv). Such an increase in intensity is not affected by the electrical stimulation of the previous step (i) and therefore allows each time to increase a new layer of muscle fibers that have not yet been strengthened. This makes the method even more accurate and easier to perform.

[0066] According to a preferred embodiment of the method, step (iv) comprises, between sub-steps (iv.1) and (iv.4), the following sub-steps: (iv.2) carrying out steps (b) and (c); Further includes:

[0067] Moreover, this introduction of sub-step (iv.2) needs to be understood together with the "charge" taken into account in each execution of this sub-step. For example, following the numerical example above, the first execution of sub-step (iv.2) induces the subsequent execution of steps (b) and (c) at a charge of 28 mA.

[0068] This sub-step (iv.2) induces electrical stimulation with isolated pulses between two performances of steps (i)-(iii). Advantageously, the successive muscle responses and forces quantified during this performance of step (c) may be used to estimate and / or measure and / or monitor muscle data information during the repeated performance of steps (i)-(iii) and / or to regulate this performance.

[0069] Such muscle data information that is particularly advantageous to monitor is the time for a muscle to exert force in response to the electrical stimulation of step (b) after performing sub-step (iv.2). Indeed, as explained below, this time can be used to monitor increased muscle fiber homogeneity over repeated performances of step (i) as the charge is increased.

[0070] Human muscles, such as the quadriceps, contain two types of fibers: "slow-twitch fibers" and "fast-twitch fibers." On the one hand, slow-twitch fibers exert low levels of force and contract slowly, but they have a predominantly oxidative metabolism and they are resistant to fatigue. On the other hand, fast-twitch fibers exert high levels of force and contract rapidly, but they have a predominantly glycolytic metabolism and are not resistant to fatigue.

[0071] It is therefore relevant to determine whether the proportion of slow-twitch and fast-twitch fibers remains the same during electrical stimulation of the muscle when increasing the charge introduced by step (iv). Indeed, if the proportion of increased fast-twitch and slow-twitch fibers changes as a function of charge during the method, this will affect the quantification of muscle fatigue in step (iii) if they have different resistance to fatigue.

[0072] An approach for monitoring this parameter during the execution of the method is to quantify (e.g., measure) the time required for the muscle to exert (i.e., reach) the force quantified in step (c) in response to electrical stimulation with an isolated pulse. Indeed, since slow and fast twitch fibers also exert their forces at different rates, variations in this time can be interpreted as variations in the proportion of slow and fast twitch fibers that are electrically stimulated.

[0073] Therefore, step (c) preferably includes quantifying the time it takes for the muscle to exert force in response to the electrical stimulation of step (b). In this case, step (iv) preferably includes the following sub-step between sub-steps (iv.2) and (iv.4): (iv.3) comparing the time quantified when performing step (c) resulting from the preceding substep (iv.2) with the time quantified when performing step (c) for the last time prior to performing step (i) for the first time; Includes.

[0074] It is therefore advantageously possible to continuously compare the time resulting from electrical stimulation with isolated pulses at a new increased charge with the original time associated with performing steps (b) and (c) following confirmation of the charge used to initially perform step (i). This makes it possible to detect potential changes in the homogeneity of the increased muscle fibres over the repeated performance of step (i), which may affect the reliability of the quantification of muscle fatigue.

[0075] In practice, this time is generally comprised between 50 and 100 milliseconds, depending on the proportion of slow-twitch and fast-twitch muscle fibers in the subject. Illustratively, it may be 60, 70, 80, or 90 milliseconds.

[0076] The execution of the method may be stopped after any execution of substep (iv.3) where the times compared in substep (iv.3) subsequently differ by at least 10 ms, more preferably at least 5 ms, in which case the proportion of slow-twitch and fast-twitch fibers increased over the repeated execution of step (i) will change too much for the quantification of muscle fatigue to be reliably ascertained.

[0077] According to another preferred embodiment of the present disclosure, any electrical stimulation of step (i) at any frequency is preceded and / or followed by a rest period of at least 300 ms. This applies regardless of whether sub-step (iv.2) (or more generally step (iv)) is performed as part of the method or not.

[0078] This rest period is advantageous because it can mitigate (or better avoid) disturbances from one electrical stimulation (of substep (iv.2) or step (i)) to another. Such disturbances can be due, for example, to muscle "tetanization", i.e. the fusion of the curve graphs of the force exerted by the muscle as a function of time in response to each of two electrical stimuli that are too close in time. The minimum limit of 300 ms is selected to allow at least one almost complete return of the muscle to a normal and / or relaxed state (i.e. no contraction and no exerted residual force) between two successive electrical stimuli.

[0079] This makes it possible to directly quantify, with very low or no quantitative disturbances, the force exerted by the muscle when performing each step (ii) for each of the frequencies of step (i) and when performing each step (c) resulting from sub-step (iv.2).

[0080] Advantageously, the rest periods also contribute to mitigating the potentiation presented above, thus making the quantification of muscle fatigue more accurate and reliable. Indeed, spacing out successive electrical stimuli in time reduces the number of electrical impulses per unit time, and therefore also reduces the potentiation in muscle fibers stimulated by these electrical stimuli.

[0081] Values ​​such as 2 / 5, 3 / 5, 4 / 5, 1, 6 / 5, 7 / 5, 8 / 5, 9 / 5, 2, 3, 4 or 5 seconds for the rest period are preferred because, on the one hand, they are long enough to strongly mitigate (and even avoid) the above-mentioned disturbances and enhancements, and, on the other hand, they are short enough in overall time to make the method easily applicable.

[0082] Different rest periods according to the preceding disclosure may be applied. For example, a first rest period may be applied between two electrical stimulations when performing the same step (i). Thus, a second rest period may be applied after the entire execution of step (i). Finally, a third rest period, if present, may be applied between the execution of step (b) resulting from sub-step (iv.2) and the execution of step (i). Any of these rest periods contribute to mitigating or avoiding the above-mentioned disturbances, but the second rest period is the one that has the greatest effect on this and on mitigating or avoiding potentiation. Therefore, the second rest period is preferably longer than the first and / or third rest periods. Preferably, the second rest period is 330 milliseconds or more, and the first and third rest periods are 300 milliseconds or more. More preferably, the second rest period is 1 second or more, and these first and third rest periods are 0.5 seconds or more. For example, the second rest period is about 5 seconds, and the first and third rest periods are about 1 second.

[0083] In particular, within the framework of the present disclosure, the term "isolated" as used in step (b) refers to the fact that the isolated pulse is separated in time from any other pulse of any other electrical stimulus, and preferably sufficiently separated for a muscle response to the isolated pulse to be achieved or at least nearly achieved (i.e. with a nearly complete return of the muscle to a normal and / or relaxed state). Preferably, this pulse is separated by at least 300 milliseconds, more preferably at least 1 second, from any other electrical stimulus of steps (b) and (i).

[0084] According to a preferred embodiment of the present disclosure, a further method is presented to increase the reliability and accuracy of the determination of muscle fatigue in step (iii). According to this embodiment, each electrical stimulation in step (i) at each frequency lasts for a maximum of 500 milliseconds. In other words, the repetition of pulses at each frequency in step (i) is performed in a short time of a maximum of 500 milliseconds.

[0085] This short time is so short that it advantageously makes it possible to avoid voluntary or reflex disturbances of the subject that could otherwise increase the force by adding muscle contractions or, conversely, decrease it by contracting antagonistic muscles to the muscle. This makes the determination of the force in step (ii) and therefore the execution of the entire method more accurate and reliable. This short time also makes it possible to reach the same maximum force determined in step (ii) at each frequency, as would still be the case by repeating the pulses at each frequency in a time of more than 500 milliseconds. This short time also advantageously reduces the overall execution time of the method.

[0086] Preferably, the short time is further comprised between 150 and 250 milliseconds. For example, it is 200, 210, 220, 230, 240 or 250 milliseconds. The above-mentioned advantages are enhanced with a short time of 250 milliseconds.

[0087] It can be pointed out that the exact time data T (in seconds) is equivalent to the exact number N of pulse data at a given frequency μ (in Hz), the number of which satisfies the formula T=N / μ. Preferably, the pulses are repeated 5-20 times during each electrical stimulation of step (i) at each of the frequencies.

[0088] According to an exemplary embodiment of the present disclosure, the frequency mentioned in step (i) is comprised between 0 and 200 Hz. Such an upper limit mitigates the induction of muscle fatigue by the implementation of the quantification method. Preferably, the frequency is between the first frequency μ 1 and the second frequency μ 2 The first frequency preferably includes 2 -μ 1 ≧μ 2 10 / 10 means that the frequency differs from the second frequency by at least 10%.

[0089] This difference between the frequencies is advantageous to ensure that two points on the curve of the force exerted by a muscle in response to an electrical stimulation at a certain frequency as a function of this frequency are sufficiently separated one from the other to perform step (iii) more accurately. This follows from the non-uniformity and non-linearity of the deformation of this curve, which depends on the pre-existing muscle fatigue. The force exerted by a muscle in response to an electrical stimulation at a low frequency (such as 0-50 Hz) is in fact more affected by this muscle fatigue than the force exerted by a muscle in response to an electrical stimulation at a high frequency (such as 50-200 Hz).

[0090] Therefore, the above difference μ 2 -μ 1 is the second frequency μ 2More preferably, the first frequency is at least 20%, and even more preferably at least 50% of the first frequency. Preferably, the first frequency is comprised between 0 and 50 Hz, and / or the second frequency is comprised between 50 and 200 Hz. Preferably, the first frequency is about 20 Hz, and / or the second frequency is about 120 Hz or 120 Hz. Any other similar value pairs for the first and second frequencies may be used, such as, for example, 10 Hz and 50 Hz, 20 Hz and 100 Hz, 30 Hz and 80 Hz, 50 Hz and 150 Hz, etc.

[0091] According to these embodiments, the frequency of the electrical stimulation used in step (i) preferably consists of a first and a second frequency. Advantageously, as will be explained hereafter, it is possible to quantify muscle fatigue in step (iii) only by considering these two forces. An advantage is that by limiting the electrical stimulation in step (i) in number and frequency, the induction of muscle fatigue is avoided. Another advantage is that it facilitates the execution of step (iii) by considering only a limited number of data. Illustratively, step (i) may include: - electrically stimulating the muscle with a repetition of 3, 4, 5 or 6 pulses at a first frequency of about 10, 15, 20 or 25 Hz for a short time period comprised between 150 and 250 milliseconds; - electrically stimulating the muscle with a repetition of 16, 17, 18 or 19 pulses at a second frequency of about 100, 110, 120 or 130 Hz for a short period comprised between 150 and 250 milliseconds; It may be composed of:

[0092] The disclosed subject matter, however, is not limited to frequencies consisting of only a first and second frequency. Other numbers of frequencies are contemplated, such as 3, 4, 5, 6, 7, 8, or more frequencies, and these frequencies may also be equally spaced within the range of frequencies.

[0093] According to a preferred embodiment of the present disclosure, step (iii) preferably comprises: - a comparison of the forces determined in step (ii), and - Quantification of muscle fatigue based on this comparison Includes.

[0094] In the above mentioned case of frequencies including the first and second frequencies, the force quantified in step (ii) is therefore a first force exerted by the muscle in response to the electrical stimulation of step (i) at a first frequency, and a second force exerted by the muscle in response to the electrical stimulation of step (i) at a second frequency. Including, Preferably, step (iii) comprises the following sub-steps: (iii.1) calculating a ratio of the first force to the second force; (iii.2) comparing the ratio calculated in substep (iii.1) against a threshold value; and (iii.3) quantifying muscle fatigue based on the comparison of substep (iii.2); Includes.

[0095] In particular, sub-steps (iii.1) and (iii.2) are therefore preferred implementations of the above-mentioned comparison of forces.

[0096] This particular implementation of step (iii) allows for an easy, fast and low-complexity calculation for quantifying muscle fatigue. It is also very efficient. In fact, since the first frequency differs from the second frequency by at least 10%, the ratio is affected by the non-uniformity of the deformation of the aforementioned curve graph of the function of muscle fatigue. Any difference identified in sub-step (iii.2) can therefore be the basis of muscle fatigue, which can be further quantified at least implicitly, and more preferably explicitly, in particular with respect to a threshold value corresponding to the ratio expected for a non-fatigued muscle.

[0097] The threshold against which the ratio of the first force to the second force is compared is preferably a numerical value F(μ 1 ) / F(μ 2), where: F is a person-independent increasing regular function of the force exerted by a non-fatigued muscle in response to an electrical stimulus as a function of the frequency of this electrical stimulus, μ 1 and μ 2 are the first and second frequencies, respectively.

[0098] Expressing the ratio in this manner is advantageous because it is person independent and is given indirectly through the function F for any pair of first and second frequencies. This example is not intended to limit the scope of the disclosed subject matter. For the above examples including only first and second frequencies, it is not necessary to consider the entire function F since the numerical values ​​corresponding to these frequencies are sufficient.

[0099] By way of example, the first frequency may be comprised between 10 and 40 Hz, the second frequency may be comprised between 90 and 130 Hz, and the threshold may be comprised between 40 and 90%. More preferably, the first frequency is about 20 Hz, the second frequency is about 120 Hz, and the threshold is about 60%, or 65%, or 70%, or 75%, or 80%.

[0100] Within the framework of this document, the terms "quantifying", "quantifying", "quantification" and any other variants preferably correspond to the terms "quantifying", "quantifying" and "quantification" in the sense that muscle fatigue is preferably not only identified but also explicitly measured and / or calculated. For example, in the above example, the explicit measurement and / or calculation may be derived from a comparison of the calculated ratio to a threshold value and / or from calculating an average value of the quantified muscle fatigue. The scope of step (iii) nevertheless does not exclude the quantification of muscle fatigue based on other physical quantities, preferably derived at least in part from the forces quantified in steps (c) and / or (ii), such as, for example, the associated rotational force. Alternatively, steps (c) and (ii) do not exclude the quantification of forces, which may be based on physical quantities related to the forces that may be measured in response to the electrical stimulation of steps (b) and (i), such as, for example, the displacement, acceleration, and / or rotational force.

[0101] According to another disclosed embodiment of the method, the forces are quantified in steps (c) and (ii) by direct force measurements, preferably by strain gauges or dynamometers. In particular, the force quantification in steps (c) and (ii) is performed directly by measuring the forces (in Newtons) by suitable techniques and without any intermediate or indirect measurements and / or observations (such as by electromyography), nor by estimations or evaluations that cause an increased risk of force quantification errors. These direct force measurements are preferably performed by dedicated muscle force measuring devices as presented hereinafter.

[0102] Preferably, the involved muscles comprise muscles of the lower limbs of the person (i.e., the subject). Preferably, the muscles comprise the quadriceps or hamstrings. In these cases, according to an exemplary embodiment of the present disclosure, the method further comprises, prior to step (a), the following steps: (α) - an apparatus for generating the electrical stimuli of steps (b) and (i), comprising a control device for selecting parameters of the electrical stimuli; - A seat that is adjusted to receive a person in a seated position and to be positioned on a horizontal support; A leg support element adapted to receive and stably maintain at least a portion of the leg of the lower limb; an instrument arranged to measure the forces determined in steps (c) and (ii) at the level of the leg support element in response to the electrical stimuli generated by the device in steps (b) and (i); and A mechanical structure mechanically connecting the seat and the leg support element and providing a connection member to the instrument at the level of the leg support element A muscle strength measuring device comprising: a logical unit, connected to an instrument such that the logic unit is adapted to receive from the instrument the force measurements determined in steps (c) and (ii); Adjusted to receive the target numerical ranges of charge and muscle force set in step (a); A logic unit configured to execute sub-steps (d.1) and (d.2) and step (iii) from the target numerical ranges of the electric charge and the muscle force set in step (a) and from the forces measured by the instruments in steps (c) and (ii). Providing a system comprising: (β) positioning the seat on a horizontal support; (γ) positioning the person on the seat in a sitting position and positioning at least a portion of the leg on the leg support element such that the lower limb is only in direct external physical contact with the muscle strength measuring device; Includes.

[0103] As will be understood by those skilled in the art, the system provided in step (α) is fully designed and configured to perform the steps of the method of the present disclosure. In particular, preferably, the target numerical ranges of charge and muscle force set in step (a) are received by the logic unit, the electrical stimulation in steps (b) and (i) are generated by the device, and the force quantified in steps (c) and (ii) is measured by an instrument. In addition, preferably, the comparison in sub-step (d.1), the correction of the charge in sub-step (d.2), and the quantification of muscle fatigue in step (iii) are performed by the logic unit based on the target numerical ranges of charge and muscle force set in step (a) and on the force measured by the instrument in steps (c) and (ii). The logic unit may also be connected to the device and / or its control device for algorithmically operating the device and / or selecting the parameters of the electrical stimulation.

[0104] The electrical stimulation parameters preferably include at least the frequency of the electrical stimulation, the charge, and the number of pulses of each electrical stimulation. Preferably, the frequency of the electrical stimulation may vary, for example, in a frequency range of 0-200 Hz. Preferably, the selection of the charge includes at least the selection of the electrical intensity of the pulses. These electrical stimulation parameters may also include the first, second and / or third rest periods mentioned above. The control device may preferably be configured to execute a predetermined charge program associated with the method. Alternatively, this execution may be under the control of a logic unit, as explained above.

[0105] The use of a muscle strength measuring device for carrying out steps (c) and (ii) is particularly advantageous: this device is very simple and easy to transport, while allowing to directly quantify the forces in steps (c) and (ii) with great accuracy. The performance of steps (b) and (i) is also made very simple, as when a person sits on the seat, his / her legs are positioned and kept stable on the leg support elements, as described in step (γ).

[0106] Preferably, the lower limbs are only in direct, external physical contact with the muscle strength measuring device, The legs of the lower legs hang in the air, and / or preferably further The entire thigh of the lower leg is placed on the seat, and / or preferably further The back of the knee comes into contact with the side of the seat.

[0107] Advantageously, this allows the force measurement conditions in steps (c) and (ii) to be perfectly known, and thus makes the force quantification more accurate and reliable, since physical disturbances (e.g. those caused by the force exerted by the foot on a support such as the ground) are avoided. Preferably, the person is positioned in steps (b) and (c) such that his back is upright and forms a substantially right angle with the thigh of the lower leg. Due to the simple structure of the device and the ease of positioning the person, the instrumental force measurement is reproducible. This is advantageous for the purposes of the disclosed method, since the muscle fatigue quantified in step (iii) can be compared at any time and anywhere throughout the day, provided that the seat can be positioned on a horizontal support, without the need to carry out the method in the same place and in the same conditions, without worrying about the variability of parameters related to the positioning of the person.

[0108] Preferably, the muscle strength measuring device is kept stationary relative to the horizontal support during the execution of steps (b), (c), (i) and (ii) by the whole weight of the person acting at the level of the seat. In particular, no complex or heavy structure is required to receive the person and to execute the method. A simple plane connected to the leg support element by a mechanical structure, as described in step (β), can be used as the seat and positioned on the horizontal support anywhere, such as a platform or another seat. In particular, it is not necessary for the person to go to a specific medical or sports facility to quantify his / her muscle fatigue. The seat is preferably wide enough to fully position the person sitting on it. It preferably extends continuously, at least 40 cm, preferably at least 50 cm or at least 60 cm, along two vertical axes.

[0109] By receiving and not simply supporting the leg, the leg support element allows for maintaining the leg portion in a fixed position, ensuring accurate and reproducible measurements of forces, for example as described. The leg support element preferably comprises a semi-cylindrical hollow portion to match the curvature of the leg portion and immobilize it laterally. The leg support element may also comprise a strap to better immobilize the leg portion.

[0110] As mentioned above, the instrument is mechanically connected to the mechanical structure at the level of the leg support element, so as to measure the forces determined in steps (c) and (ii) at the level of the leg support element. The instrument is typically aligned with the direction of the forces, so as to measure these forces directly and accurately. It may be aligned with the leg support element and form a single part therewith, so that, in other words, it is fixed directly to the leg support element. As mentioned above, the instrument is preferably a strain gauge or a dynamometer. It can be arranged to operate in traction or in compression, so that a reproducible, direct and accurate measurement of the forces can be performed.

[0111] The mechanical structure is preferably composed of a mechanical arm or a mechanical frame. Advantageously, the structure of the device is therefore very simple and light. The arm or frame may have a simple shape, for example a protruding shape of "I", "L", "T", "U", "S" or "Z", in at least one plane perpendicular to the seat, and may preferably comprise at least one higher extremity that is connected (or fixed) to the seat and at least one lower extremity that is connected (or fixed) to the leg support element. The device may comprise position adjustment elements for correcting the position and / or orientation of the mechanical structure relative to the seat and / or the position and / or orientation of the leg support element relative to the mechanical structure. Such position adjustment elements may comprise any mechanical element known to the person skilled in the art, such as a screw, a bolt, a pin, a spring, etc., preferably configured to cooperate with the mechanical arm or frame, for example in a cavity.

[0112] The muscle strength measuring device preferably consists only of a seat, leg support elements, a scale, a mechanical structure and, if present, a position adjustment element. It is thus simplified to a very simple and practical form, but allows to carry out steps (c) and (ii) of the method in an accurate manner to quantify muscle fatigue.

[0113] The disclosed subject matter also provides a system as described in detail above as a system for quantifying muscle fatigue in a muscle, the system also being adapted to carry out the disclosed method. All embodiments of the method according to the present disclosure, and the advantages of these embodiments, apply mutatis mutandis to the present system according to the present disclosure. In particular, the system allows for reliable and accurate quantification of muscle fatigue, as discussed above.

[0114] The disclosed subject matter is further presented in the claims. As will be understood by those skilled in the art from this disclosure, any one of the embodiments presented in these claims may be considered alone or in combination. In particular, where possible, the dependencies of the claims may be considered in a broader manner, so that any one of the possible combinations of the claims are part of this application, as long as they are technically possible and understood by those skilled in the art, especially in view of this disclosure.

[0115] Other features and advantages of the disclosed subject matter will become apparent from a reading of the following detailed description, for the understanding of which reference is made to the accompanying drawings. [Brief description of the drawings]

[0116] [Figure 1] 1 is a flow diagram of a method according to an exemplary embodiment of the present disclosure. [Diagram 2] FIG. 13 illustrates experimental continuous force measurements as a function of time during step (b) of a method according to a representative embodiment of the present disclosure. [Diagram 3]1 is an experimental curve graph of the force measured in step (c) of a method according to an exemplary embodiment of the present disclosure as a function of the electrical intensity of an isolated pulse of step (b); [Figure 4] 1 is a curve graph of the (total and / or maximum) force exerted by a muscle in response to electrical stimulation of step (i) at a certain frequency as a function of this frequency. [Diagram 5] FIG. 2 illustrates experimental continuous force measurements as a function of time during step (i) of a method according to a representative embodiment of the present disclosure. [Figure 6] FIG. 2 illustrates an example of a muscle strength measuring device in a system for implementing an exemplary embodiment of the disclosed method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0117] The drawings in the figures are not to scale. Similar elements may be assigned similar reference numbers in the figures. Within the framework of this document, identical or similar elements may have the same reference numbers. The presence of reference numbers in the drawings shall not be considered limiting, especially when these numbers are presented in the claims.

[0118] A description of alternative embodiments of the disclosed subject matter is given below with reference to figures, but the disclosure is not limited by these references. In particular, the drawings or figures described below are only schematic and are in no way limiting.

[0119] As shown in FIG. 1, the exemplified muscle fatigue quantification method includes, in step (ii), 1 , μ 2 , μ 3 , , μ n The respective (maximal) forces F exerted by the muscle in response to each of the electrical stimuli at 1 , F 2 , F 3 , , F n In order to quantify and preferably measure them, in step (i) different frequencies μ1 , μ 2 , μ 3 , , μ n and finally, in step (iii), electrically stimulating the muscle with the force F so determined. 1 , F 2 , F 3 , , F n The present invention aims to quantify muscle fatigue based on the number of electrical stimulations.

number

[0120] The electrical stimulation of step (i) is carried out with an electric charge E, which corresponds to the electrical intensity of the pulse with which any of these electrical stimulations are performed. The electric charge E is typically comprised between 10 and 100 mA.

[0121] In order to use the charge E to enable accurate and reliable determination of force in step (ii) and quantification of muscle fatigue in step (iii), the method comprises steps (a) to (d) as described above. In step (a), an initial charge E 0 is set to, for example, 15 mA, 20 mA or 25 mA. This charge is selected as an intermediate charge convenient for a wide variety of subjects in order to perform steps (i)-(iii) reliably. Step (a) also contemplates setting a target numerical range I of muscle force. Preferably, the numerical range I is a numerical range of the form [L,+∞[ or ]L,+∞[, where L is a lower limit, for example 5N, as detailed in the subject disclosure.

[0122] As illustrated in FIG. 1, the charge E:=E 0is used to define and execute electrical stimulation of the muscle with isolated pulses in step (b), and to quantify the (maximal) force F exerted by the muscle in response to the electrical stimulation in step (c). If F∈I, step (i) is performed by setting E=E 0 If not, then via step (d), the charge E is modified as E', and steps (b)-(c) are performed again with the new charge E, resulting in the determination of a new force F and a re-evaluation of the condition F∈I via step (d). In particular, E corresponds to an iteration parameter that is iteratively modified by a modified value, abstractly noted as E', until the condition F∈I is satisfied, as fully explained in the present subject disclosure.

[0123] Advantageously, as shown in FIG. 3, the curve graph 66 showing the empirical measurement of any such force (read in Newtons on axis 82) determined in step (c) with varying charge (read in mA on axis 85) is substantially linear, at least for charges in the range of interest for the iteration of steps (b) to (d). In fact, in most circumstances, the charge used when performing step (i) for the first time will be comprised between 25 and 40 mA. As a result, it may be easy to determine the charge E' to be corrected in step (d) simply by applying to the current charge E a ratio guided by the slope of the curve graph. As the slope of the curve graph is muscle dependent, it is obtained by the ratio of the reference force (preferably L, or L+1 / 2N, or L+1N) to the force F finally determined in step (c).

[0124] The time T for the muscle to exert the force F quantified in step (c) is quantified at least at the last time step (c) is performed before the first time step (i) is performed, and optionally at the time of each preceding step (c), if any. This time is T 0 It is abbreviated as :=T.

[0125] FIG. 2 shows the continuous force measurements (read on axis 82 in Newtons) as well as the maximum force F quantified in step (c) as a function of time (read on axis 83 in milliseconds) during the execution of step (b). In particular, the curve graph 65 derived from this measurement corresponds to the response of the muscle to an isolated pulse with a current charge E. This response is called "twitch". Time 0 corresponds to the moment when the pulse is applied at the level of the muscle. As can be obtained from the curve graph 65, the force F is reached after a time T generally comprised between 50 and 100 milliseconds. The force exerted by the muscle is progressively reduced until the muscle returns to a normal state, without any contraction due to electrical stimulation with an isolated pulse and without any exerted and residual force. Such a normal state is in particular reached approximately after 180 milliseconds and mainly after 300 milliseconds.

[0126] To further increase the accuracy and reliability of the method, steps (i) to (iii) are repeated with increasing charge, as explained above and shown in FIG. 1. The charge E is first incremented as E+ in sub-step (iv.1). Steps (b) and (c) are then performed with this charge E (further described as a parameter of the current electrical stimulus) in sub-step (iv.2), so that the force F and the time T are newly determined in step (c) with this updated charge. The time T is preferably incremented as T in sub-step (iv.3). 0 and the new iterations of steps (i)-(iii) are preferably compared to TT to ensure that the muscle fibers added over the repetitions of the execution of step (i) remain homogenous in terms of slow-twitch and fast-twitch fibers. 0 ≒0 (e.g., |TT 0 |<5 ms), then it is executed as substep (iv.4).

[0127] The quantification of muscle fatigue during each step (iii) can be done, for example, by using two forces F 1 and F 2 Calculate the ratio of and / or F for 1 ≤ j ≤ n j ~μ jThis may be done by discrete integral calculations on a function for , and comparing at least one of these calculations to at least one expected value.

[0128] FIG. 4 shows a graph of the (maximum) force (read in Newtons on axis 82) exerted by a muscle in response to an electrical stimulus as a function of frequency (read in Hertz on axis 81). In other words, each point on each graph represents a force that can be determined in step (ii) in response to an electrical stimulus at one of the frequencies of step (i). Curve graph 61 corresponds to a graph of a theoretically expected function F, which represents the force exerted by a non-fatigued muscle in response to a possible electrical stimulus as a function of the frequency of such an electrical stimulus. Curve graph 62 shows the points (μ) measured for a fatigued muscle. 1 ,F 1 ), (μ 2 ,F 2 ), (μ 3 ,F 3 ), , (μ n ,F n ) and a continuous and regular spread of dots clouds corresponding to the frequency of the muscle. It is noted that the interval between the two curve graphs 61 and 62 is larger over low frequencies (e.g., 10-40 Hz) than over high frequencies (e.g., above 90 Hz). This interval corresponds to the difference 71 and 72 between the force measured for the muscle and the force expected from the function F for an unfatigued muscle at low and high frequencies, respectively. In particular, the difference 72 is so small that it can be assumed that the two curve graphs 61 and 62 are substantially the same for the high frequencies.

[0129] If it is assumed that the ratio F(20) / F(120) is known theoretically or in practice to be 65%, then it is 1 = 20Hz and μ 2 = Force in response to electrical stimulation at 120 Hz F 1 and F 2 In practice, F 2corresponds essentially to F(120), so F 2 The measurement of F corresponds in some sense to the reference measurement. 1 The measurement of F 2 It allows us to clearly show the deviation from the expected value in terms of the ratio to the 1 / F 2 Muscle fatigue is considered to be quantified by the method and can be quantified if μ significantly differs from 65%. This value of about 65% for the ratio is meant to be illustrative and not limiting. Other values ​​such as about 75% or 85% may also be convenient depending on the function F considered. Similarly, μ 1 and μ 2 The value of is in no way limiting. For example, the exact same argument could be applied to a frequency of μ instead of 120 Hz. 2 =100Hz.

[0130] Force F for the muscles of the lower limbs 1 , F 2 , F 3 , , F n A muscle strength measuring device 1 for measuring muscle strength is illustrated in Figure 6. It is preferably part of an overall system arranged to carry out the methods as described in the present subject disclosure.

[0131] The device 1 comprises a seat 10 with a flat part 11 for receiving a person in a seated position, a rigid frame 12 for the flat part 11 and a positioning lower part 13 for removably positioning the seat on a horizontal support. The rigid frame 12 contributes to the rigidity of the seat 10, especially at the level of the flat part 11, which may be made of soft and / or padded material for the comfort of the person. The positioning lower parts 13 may be adjustable in height from 0 to 1 / 20 meter below the flat part 11 to improve the stability of the seat 10 on the horizontal support. They may be suction cups. They may have protected tips. They are not arranged to be placed on the ground, since another part of the device 1 extends lower than them.

[0132] The device 1 comprises, as illustrated, a leg support element 3 fixed to a seat 10 by a mechanical structure 2. The mechanical structure 2 is in particular a mechanical frame in the device 1 illustrated in FIG. 6. The leg support element 3 comprises a semi-cylindrical hollow part for receiving and at least partially immobilizing the lower part of the leg of the lower limb. A measuring instrument 4 is also provided for measuring any force exerted by the muscle at the level of the leg support element 3, in particular in response to an electrical stimulus, when it is received and maintained by the leg support element 3. The mechanical structure 2 also comprises a connecting member 5 to the measuring instrument 4 at the level of the leg support element. In particular, in the illustrated configuration of FIG. 6, the measuring instrument 4 is a strain gauge sandwiched between the leg support element 3 and the connecting member 5 and fixed along a first direction.

[0133] The strain gauge is provided with a connection tip 41 for connecting the device 1 to a logic unit, not shown, of the disclosed system. The logic unit is connected to a frequency μ 1 , μ 2 , μ 3 , , μ n A force F quantified by the device 1 in response to electrical stimulation at each of the 1 , F 2 , F 3 , , F n The method is configured to quantify muscle fatigue based on at least some of the following:

[0134] The connecting member 5 comprises a position adjustment element 51 for changing the position of the leg support element 3 and the instrument 4 relative to the mechanical structure 2 along a second direction d which is perpendicular to the above-mentioned first direction.

[0135] I 0Let be the electrical intensity corresponding to the charge E defined from steps (a) to (d), or in other words the electrical intensity used to perform step (i) for the first time. This electrical intensity is preferably comprised between 10 and 50 mA, typically around 25 mA. Consider a step S of charge between +0.1 mA and +5 mA, preferably around +1 mA. Let K be an integer (the so-called "number of passes") comprised between 5 and 30, preferably around 10 or 15. The execution of steps (i) to (iv) of the method according to an exemplary embodiment of the disclosed subject matter then comprises the following steps: Successively, for each integer k from 0 to K, - Time T less than 250 ms 1 N in 1 The first frequency μ 1 electrically stimulating the muscle (preferably at (about) 20 Hz), Pulse of constant duration and intensity I 0 + kS, - The (maximal) force F exerted by the muscle in response to this electrical stimulus 1 Quantifying a first rest period R of between 300 ms and 5 s, preferably (approximately) 1 s; 1 a step of waiting in - Time T less than 250 ms 2 N in 2 The second frequency μ 2 electrically stimulating the muscle (preferably at (about) 120 Hz), Pulse of constant duration and intensity I 0 + kS, - The (maximal) force F exerted by the muscle in response to this last electrical impulse 2 Quantifying - quantified force F 1 and F 2 Quantifying at least one muscle data information, preferably muscle fatigue, of a muscle based on a second rest period R of 330 ms to 10 s, preferably (approximately) 5 s;2 A step of waiting Includes.

[0136] Although sub-steps (iv.2) and (iv.3) are not mentioned above, they may be expressly integrated into the preceding list of steps, as explained above in the present subject disclosure and in the detailed description.

[0137] formula T 1 =N 1 / μ 1 and T 2 =N 2 / μ 2 It may be noted that N represents the relationship between the number of pulses, the time of electrical stimulation, and the frequency of electrical stimulation. 1 is μ 1 is (approximately) 20Hz, then N 2 is μ 2 When the maximum force F is about 120 Hz, the number of pulses is about 18. 1 and F 2 The number of electrical stimulations T was set to allow the force to reach a certain value and to avoid any disturbances in the force measurements. 1 and T 2 For example, N 2 is considered to be 25, then T 2 is still less than 250 ms, but the (maximum) force F 2 is N 2 remains substantially unchanged compared to when N is 18. 1 and N 2 These values ​​of, in particular, μ 1 and μ 2 As a preferred embodiment of the present disclosure related to the above values ​​of , have been experimentally derived by the present inventors.

[0138] FIG. 5 shows the maximum force F determined in step (c) as a function of time (read on axis 83) during partial execution of the disclosed method according to the representative embodiment presented above. 1 or F 25, but also illustrates a purely schematic curve graph 63 of the continuous force (typically contractile force) (read in Newtons on axis 82) exerted by the muscles of a person's lower limbs.

[0139] In particular, this figure illustrates the effect of electrical stimulation for any k, and thus including the entire execution of step (i). The curve graph 63 shows the effect of the second rest period R 2 It can easily be derived that the curve graph 63 subsequently repeats itself in a similar manner. If substep (iv.2) is included in the embodiment under consideration, curve graphs similar to the above-mentioned curve graph 65 of Fig. 2 are simply inserted successively between similar repetitions of the curve graph 63. Each curve graph similar to the curve graph 65 is inserted in a numerical range [0,R 3 ], where R3 is a third rest period of between 300 ms and 5 seconds, preferably (approximately) 1 second.

[0140] The code T presented above 1 , R 1 , F 1 , T 2 , R 2 , F 2 applies equally to FIG. 5. Like curve graph 65, curve graph 63 is based on experimental measurements. It is reproduced generally without showing explicit experimental data. In addition, axes 82 and 83 in FIG. 5 are not necessarily given to a linear scale. In particular, for the sake of clarity, the number of times N corresponding to the illustration in FIG. 1 and N 2 are three and five times, respectively, and time T 1 , R 1 , T 2 and R 2 are not evenly scaled on axis 83.

[0141] The muscle is a pulse of a certain duration and I 0 +kS and for a time T shorter than 250 milliseconds 1 The first frequency μ 15. The occurrence of each pulse corresponds to a scale line 84 on the time axis 83. The effect of the pulses on the curve graph 63 is represented by 64 and is clearly visible as a gradual increase in the force exerted by the muscle due to the muscle contraction and therefore the tetanic process. In other words, the pulses generated at 84 are close enough together that a kind of fusion of the effect of each individual pulse on the muscle occurs at a time T 1 and therefore, at time T 1 Such a stepped portion of the curve graph 63 is obtained.

[0142] The same argument applies when the pulses are of the same constant duration and I 0 +kS, for a time T shorter than 250 ms 2 The second frequency μ 2 >μ 1 The method is applied to the electrical stimulation of a muscle in step (i).

[0143] Each time T 1 and T 2 Frequency μ 1 and μ 2 Each of these electrical stimulations at 1000 Hz produces a maximum force, F, exerted by the muscle in response to the electrical stimulation, as visible in axis 82 of FIG. 1 and F 2 5, the first and second rest periods R 1 and R 2 is long enough to allow the muscle to return to a "normal" and / or "relaxed" state without any contraction due to the previous electrical stimulation, any residual force exerted, and before the start of the next electrical stimulation. In other words, the rest period R 1 and R 2 allows the curve graph 63 to return to the baseline. The rest period R 1 Form I 0 +kS with the same pulse strength and frequency μ 1 and μ 2The rest period R 2 is the pulse intensity I 0 + kS with frequency μ 2 Electrical stimulation at pulse intensity I 0 +(k+1)S with frequency μ 1 Electrical stimulation with a pulse intensity I 0 +(k+1)S)

[0144] As described in this disclosure, the method includes: 1 and F 2 5 also illustrates, in dotted lines, an example of the effect of such disturbances 91, 92 and 93 on the curve graph 63. They are purely imaginary, as methods are specifically envisaged to avoid them.

[0145] The disturbance 91 is the first rest period R 1 4 shows an example of a tetanic effect on the curve graph 63 due to not following the lower limit discussed above for F. If this period is not sustained sufficiently, the muscle will still be contracted and not relaxed when the next electrical stimulation begins, thereby causing F 2 The measurement of frequency μ 1 and μ 2 The effect of electrical stimulation in the vertebral column is excessively high due to partial (tetanic) fusion. 1 ), nevertheless, a straightforward mathematical treatment (e.g., by linear interpolation) can be applied to extract the force F from the observed disturbed curve graph 91. 2 A similar argument can obviously be made for the second rest period R 2 can be applied to.

[0146] Disturbance 92 occurs at time T 1An example of the enhancement effect is shown on the curve graph 63 above (though one skilled in the art would readily appreciate that such an effect is not limited to this time period). By not increasing the pulse strength with charge steps S during successive performances of step (i), the muscle is enhanced, resulting in an actual force F 1 is disturbed by certain exercises of muscle fibers, in particular by being greater than it should be. The increase in intensity during successive performances of step (i) according to the present disclosure makes it possible to avoid such an enhancing effect.

[0147] Finally, disturbances 93 represent instances of voluntary and / or reflexive muscle contractions by the subject, parallel to the electrical stimulation. The subject increases its force during the pulse and decreases it between or after the pulse. Advantageously, such disturbances are long enough for the subject to react on his own during the electrical stimulation, for a time T 1 and T 2 If is very short (max 500ms, preferably less than 250ms) this will not happen.

[0148] It will be readily understood by those skilled in the art that the number of electrical stimuli n for this type of embodiment is equal to 2, however, these embodiments can be easily generalized to any number n>1.

[0149] In other words, the disclosed subject matter detailed above relates to a method for quantifying muscle fatigue, comprising the steps of electrically stimulating a muscle with charges at different frequencies, the charges being iteratively determined to generate reliable and accurate forces in the muscle in response to the electrical stimulation, the method further comprising quantifying these forces and muscle fatigue based thereon.

[0150] The disclosed subject matter has been described above in relation to specific examples, which have values ​​that are purely illustrative and should not be considered limiting. Those skilled in the art will recognize that the disclosed subject matter is not limited to the examples illustrated and / or described hereinabove. The disclosed subject matter includes each of the novel technical features described in this document, and combinations thereof. All embodiments and advantages of the method apply mutatis mutandis to the sports activity planning method described above.

Claims

1. 1. A method for collecting data regarding muscle fatigue of a muscle, comprising the following steps in the following order: (a) setting target numerical ranges (I) of electric charge (E) and muscle force in a logic unit; (b) electrically stimulating said muscle with isolated pulses of said charge (E) by an electrical stimulation generating device; (c) measuring the force (F) exerted by the muscle in response to the electrical stimulation of step (b) by means of a muscle strength measuring device (1); (d) if the force (F) measured in step (c) does not fall within the target numerical range (I) of muscle strength, (d.1) comparing, by the logic unit, the force (F) measured in step (c) with a target numerical range (I) of muscle force; (d.2) modifying, by said logic unit, said charge (E) in response to said comparison of substep (d.1); and (d.3) repeating steps (b) to (d); (i) The electrical stimulation generating device generates electrical stimulation at different frequencies (μ １ , μ ２ , μ ３ , ..., μ ｎ ) electrically stimulating said muscle with said charge (E); (ii) measuring the force (F) exerted by the muscle in response to the electrical stimulation of step (i) by the muscle strength measuring device (1); １ , F ２ , F ３ , ..., F ｎ ) measuring the (iii) the logic unit calculates the force (F １ , F ２ , F ３ , ..., F ｎ collecting data regarding said muscle fatigue based on A method comprising:

2. 2. The method of claim 1, wherein the charge (E) is defined by the electrical intensity of the pulses constituting the electrical stimulus, such that the modification of the charge (E) in substep (d.2) corresponds to a modification of the electrical intensity.

3. 3. The method according to claim 1 or 2, wherein the comparison in sub-step (d.1) comprises determining a ratio of a reference force of a target numerical range (I) of muscle force to the force (F) measured in step (c).

4. The method of claim 3 , wherein the reference force is selected from a lower limit or an upper limit of a target numerical range of the muscle force, the lower limit increased by a force step, or the upper limit decreased by a force step.

5. The modification of the charge (E) is determined in substep (d.2) by the formula E′F=EF′, where: E is the charge, E' is the modified charge to be determined, F is the force measured in step (c), F' is the reference force; The method according to claim 3.

6. A method according to claim 1 or 2, wherein a target numerical range (I) of the charge (E) and / or the muscle strength is set in step (a) for the muscle and / or depending on at least one technical feature of the muscle strength measuring device (1).

7. the charge (E) set in step (a) is comprised between 10 and 40 mA, and / or The lower limit (L) of the target numerical range (I) of the muscle strength set in step (a) is included in the range of 2 to 10 N; The method according to claim 1 or 2.

8. Step (iii) is followed by the step of: (iv) (iv.1) increasing, by said logic unit, said charge (E) by a charge step (S); (iv.4) Repeating steps (i) to (iii). The method according to claim 1 or 2, comprising performing the steps of:

9. Step (iv) further comprises, between sub-steps (iv.1) and (iv.4), the following sub-steps: (iv.2) carrying out steps (b) and (c). The method of claim 8 , comprising:

10. 10. The method of claim 9, wherein step (c) further comprises measuring the time (T) for the muscle to exert the force (F) in response to the electrical stimulation of step (b).

11. Step (iv) further comprises, between sub-step (iv.2) and sub-step (iv.4), the following sub-step: (iv.3) The time (T) measured by the logic unit when it last performs step (c) before it first performs step (i). ０ comparing said time (T) measured when performing step (c) resulting from sub-step (iv.2) above with The method of claim 10, comprising:

12. The execution of the method is performed at the times (T, T) compared in substep (iv.3). ０ 12. The method of claim 11, wherein the sub-steps (iv.3) are stopped after any of the sub-steps (iv.4) separated by at least 10 milliseconds.

13. Each frequency (μ １ , μ ２ , μ ３ , ..., μ ｎ 9. The method according to claim 8, wherein each electrical stimulus of step (i) in sub-step (iv.1) comprises a repetition of pulses at an electrical intensity comprised between 10 and 100 mA, and wherein the increase in the charge (E) in sub-step (iv.1) corresponds to an increase in the electrical intensity of the pulses, and wherein the charge stages (S) are comprised between +0.5 and +5 mA.

14. 9. The method of claim 8, wherein the number of times step (iv) is performed is comprised between 5 and 30 times.

15. Each frequency (μ １ , μ ２ , μ ３ , ..., μ ｎ 3. The method of claim 1 or 2, wherein each electrical stimulus of step (i) in is preceded and / or followed by a rest period of at least 300 milliseconds.

16. Each frequency (μ １ , μ ２ , μ ３ , ..., μ ｎ 3. The method of claim 1 or 2, wherein each electrical stimulus of step (i) in (a) lasts for a maximum of 500 milliseconds.

17. The frequency of step (i) is A first frequency (μ １ ), and A second frequency (μ ２ ) Including, The first frequency (μ １ ) is the second frequency (μ ２ ) by at least 10%; The force measured in step (ii) is The first frequency (μ １ a first force (F) exerted by the muscle in response to the electrical stimulation of step (i); １ ), and The second frequency (μ ２ a second force (F) exerted by the muscle in response to the electrical stimulation of step (i); ２ ) Including, Step (iii) comprises the following sub-steps: (iii.1) the second force (F ２ ) against the first force (F １ ) the sub-step of calculating the ratio of (iii.2) comparing the ratio calculated in substep (iii.1) against a threshold; and (iii.3) collecting data regarding said muscle fatigue based on said comparison of substep (iii.2). The method of claim 1 or 2, comprising:

18. The method according to claim 1 or 2, wherein the muscle fatigue is long-lasting peripheral muscle fatigue.

19. 1. A method for planning a sporting activity, comprising the steps of: (0) identifying muscles stimulated during said sports activity; (1) performing the method according to claim 1 or 2 to collect data on muscle fatigue of the muscles identified in step (0); and (2) planning the sports activity based on the data regarding the muscle fatigue collected in step (1); The method includes:

20. The muscle is a muscle of a human lower limb, and the method further comprises, prior to step (a), the steps of: （α） - an electrical stimulation generating device for generating the electrical stimulation of steps (b) and (i), comprising a control device for selecting parameters of the electrical stimulation; The muscle strength measuring device (1), a seat (10) adapted to receive said person in a seated position and to be positioned on a horizontal support; a leg support element (3) adapted to receive at least a portion of the leg of said lower limb and to keep it stable; The forces (F, F) measured in steps (c) and (ii) at the level of the leg support element (3) in response to the electrical stimuli generated by the electrical stimulation generating device in steps (b) and (i). １ , F ２ , F ３ , ..., F ｎ ) and a mechanical structure (2) mechanically connecting said seat (10) and said leg support element (3) and comprising a connection member (5) to said instrument (4) at the level of said leg support element (3); The muscle strength measuring device (1), said logical unit, to the meter (4), so that the logic unit receives from the meter (4) the forces (F, F) measured in steps (c) and (ii). １ , F ２ , F ３ , ..., F ｎ ) is adjusted to receive measurements of Adjusted to receive the charge (E) and the target numerical range (I) of muscle force set in step (a); From the charge (E) and the target numerical range (I) of the muscle force set in step (a), and the force (F, F) measured by the meter in steps (c) and (ii), １ , F ２ , F ３ , ..., F ｎ ), to sub-steps (d.1) and (d.2), and step (iii), Providing a system comprising: (β) positioning the seat (10) on the horizontal support; (γ) positioning the person on the seat (10) in the sitting position and positioning at least a portion of the leg on the leg support element (3) such that the lower limb is only in direct external physical contact with the muscle strength measuring device (1). Further comprising: The charge (E) and the target numerical range (I) of the muscle force set in step (a) are received by the logic unit, the electrical stimulation in steps (b) and (i) is generated by the electrical stimulation generating device, and the force (F, F) measured in steps (c) and (ii) is calculated. １ , F ２ , F ３ , ..., F ｎ ) is measured by the meter (4), and the comparison in sub-step (d.1), the correction of the charge (E) in sub-step (d.2) and the collection of data on the muscle fatigue in step (iii) are performed to the target numerical range (I) of the charge (E) and the muscle force set in step (a), and the force (F, F) measured by the meter (4) in steps (c) and (ii). １ , F ２ , F ３ , ..., F ｎ ) executed by the logic unit based on 3. The method according to claim 1 or 2, wherein the strength measuring device (1) is kept stationary relative to the horizontal support during steps (b), (c), (i) and (ii) by the entire weight of the person acting at the level of the seat (10).

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