Muscle fatigue quantification method

Abstract

A method for quantifying muscle fatigue in a muscle includes electrically stimulating the muscle with a given charge at different frequencies, quantifying the force exerted by the muscle in response to the electrical stimulation, and quantifying muscle fatigue based on the force, the steps being repeated a number of times with increasing charge, the charge being increased by a charging step between two electrical stimulation steps.

Description

[Technical Field]

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

[0002] Animal activity, particularly human activity, can induce "fatigue." Such fatigue can be neurological (i.e., induced by intellectual or mental activity) or physical (i.e., induced by physical work). Physical fatigue is also called "muscle fatigue" because it results from muscle work and leads to a decrease in the force that can be exerted by the affected muscles. In particular, muscle fatigue can lead to the inability to sustain and / or repeat a physical load. As a result, 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 exercise efficiency, preventing injuries, devising personalized sports exercise programs, preparing muscles, etc.), or in physical therapy for muscle rehabilitation (for the purposes of, e.g., monitoring physical activity, optimizing treatment, preventing overtreatment, etc.), and more generally in medicine.

[0003] A known method for assessing a subject's muscle fatigue is to perform a test requiring multiple repeated maximal voluntary contractions of the muscle (e.g., through voluntary exercise). Muscle fatigue is considered to be determined when a predetermined maximum muscle force cannot be reached according to the monitored data (time, speed, force, power output, acceleration, etc.). However, the subject's motivation to reach the maximum contraction may affect such muscle fatigue assessment. Furthermore, since the test itself induces significant muscle fatigue, the test itself affects the results obtained by the method. The test typically cannot be repeated multiple times, and it cannot be performed after strenuous muscle work (e.g., after a sports competition). In addition, this method has the disadvantage of exposing the subject to the risk of injury. Therefore, it is desirable to develop an improved method for quantifying muscle fatigue. Summary of the Invention [Problem to be solved by the invention]

[0004] It is an object of the disclosed subject matter to provide a more efficient, safe, and adaptable method for quantifying muscle fatigue. In particular, it is an object of the disclosed subject matter to provide a method that allows for the quantification of muscle fatigue without inducing muscle fatigue itself, regardless of the subject's will, at any time, and without exposing the subject to risk of injury. [Means for solving the problem]

[0005] To this end, the disclosed subject matter comprises the steps of: (i) electrically stimulating a muscle with a given charge 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); (iv) repeating steps (i), (ii) and (iii) a number of times with increasing charge, The charge in step (i) is increased by a charging step between two executions of step (i). The present invention provides a method for quantifying muscle fatigue in a muscle, comprising: The electrical stimulation typically involves repetition of pulses at each frequency.

[0006] The method according to the present disclosure is a more efficient, safer, and more adaptable method for quantifying muscle fatigue than methods described in the prior art. Indeed, the use of electrical stimulation in step (i) allows for stimulating muscles to any degree of fatigue and for the muscles to involuntarily exert force in response to the electrical stimulation. This step can therefore be performed at any time, even after sports practice, without exposing the subject to the risk of injury, and it does not depend on the subject's willingness to maximally contract the muscle. This step (i) also does not induce muscle fatigue, provided that the number of electrical stimulations is preferably limited and performed for a short period of time to observe the muscle's response and to quantify the force in step (ii). Advantageously, muscle fatigue before and after the quantification method is substantially the same.

[0007] This method of quantification allows for efficient quantification of muscle fatigue. Indeed, the inventors have noticed that muscle fatigue non-uniformly distorts the curve of the force exerted by a muscle in response to electrical stimulation at a certain frequency as a function of this frequency, and therefore it is possible to quantify muscle fatigue in step (iii) based on the quantification of this force at different frequencies, for example by comparing the force exerted by the muscle. This has the great advantage of being independent of the context in which the quantification method is performed. In particular, it does not require comparison with such a standard known curve at rest for the subject, nor does it require preliminary measurements or specific execution conditions.

[0008] Step (iv) allows for a range of quantitative values ​​(e.g., measurements) of muscle fatigue to be obtained, so that muscle fatigue can be accurately quantified with an advantageously very small margin of error. Nevertheless, this example must address another phenomenon, as presented below.

[0009] This embodiment of the present disclosure mitigates or even avoids a known muscle physiology phenomenon described in the scientific literature on muscle physiology called "potentiation" (or post-activity potentiation, or staircase phenomenon, or post-repetitive stimulation potentiation). This phenomenon is defined as the effect of preceding muscle activity on the enhancement of subsequent muscle contractions. Muscle activity therefore 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 types of muscle activity. Therefore, when electrically stimulating muscles to quantify muscle fatigue, electrically induced muscle contractions generate potentiation in stimulated muscle fibers, which masks muscle fatigue and disrupts its quantification. This disturbance is even more significant because the electrical stimulation pulses are numerous and repeated within a defined time period. Therefore, the present disclosure allows for a series of electrical stimulations at different frequencies to layers (or hierarchies) of muscle fibers that are not always the same each time step (i) is performed (i.e., performing step (i) more than once) by increasing the charge in step (i) with a charging step between two times of step (i), allowing for the inclusion of new fibers that have not yet been strengthened by the previous stimulation episode.

[0010] During a given application of step (i), fibers that are electrically stimulated at different frequencies, allowing for two or more maximum force ratios, are not yet potentiated. Then, higher charges in subsequent applications of step (i) thus add additional layers of muscle fibers that were not potentiated by the previous application of step (i). Thus, by increasing the charge in each application of step (i), the spatial expansion of muscle fibers is modified to include new fibers that were not yet potentiated by the previous application of step (i).

[0011] The quantification method according to the present disclosure is useful for a wide range of applications, particularly for quantifying muscle fatigue in professional athletes before, during or after practice or competition, as well as in injured and / or elderly individuals undergoing muscle rehabilitation.

[0012] The quantification methods according to the present disclosure are particularly useful for planning sports practice. The methods according to the present disclosure are typically not intended to be applied for therapeutic purposes and are not intended to identify or elucidate pathologies.

[0013] 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: (0) identifying the muscles stimulated during sports activities; (i) electrically stimulating the muscle with a given charge 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); (iv) repeating steps (i), (ii) and (iii) a number of times with increasing charge, the charge in step (i) is increased by a charging step between two executions of step (i); (v) planning a sports activity based on the muscle data information; A method comprising:

[0014] Preferably, all, any or at least one of the muscle data information determined when performing step (iii) is used in step (v) to plan a sports activity.

[0015] Preferably, the sports activity is a sports practice. Preferably, the muscle data information comprises (or possibly consists of) muscle fatigue (data). The method for planning a sports activity is non-therapeutic and / or non-medical and / or non-therapeutic. In particular, no therapeutic diagnosis is made in step (v), which is strictly of a planning nature. Preferably, step (v) comprises (or possibly consists of) quantifying time data dependent on the muscle data information.

[0016] If the muscle data information includes (or possibly consists of) muscle fatigue (data), the sports activity planning method comprises the following steps: (0) identifying the muscles stimulated during sports activities; (1) performing a quantification method according to the present disclosure to quantify muscle fatigue (or muscle fatigue data information) for the muscles identified in step (0); (v) planning a sports activity based on the muscle fatigue quantified in step (1); This can be rephrased as including:

[0017] In other words, step (1) corresponds to the above steps (i) to (iv), including the increase in charge between two executions of step (i). The muscle fatigue (data information) quantified in step (1) is preferably obtained from all, any, or at least one of the muscle fatigue (data) quantified when different steps (iii) are executed, more preferably by calculating the average value of all of these muscle fatigue (data).

[0018] More generally, the method of quantification according to the present disclosure may also be configured as a non-therapeutic and / or non-medical and / or non-therapeutic method of quantifying muscle fatigue in a muscle, comprising steps (i)-(iv) including an increase in charge between two repetitions of step (i). Preferably, in this case, no therapeutic diagnosis is made from step (iii) and / or, in other words, any step of therapeutic diagnosis estimation from the muscle fatigue quantified in step (iii) is excluded from the method.

[0019] Any of the following examples and advantages of the quantification method according to the present disclosure, as generally described in the introduction of this disclosure, apply mutatis mutandis to the specific particulars of the methods disclosed above, 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.

[0020] Another advantage of the quantification method of the present disclosure is that it allows for the quantification of specific muscle fatigue. In fact, muscle fatigue depends on many physiological factors. In particular, muscle fatigue can be caused by defects in neuromuscular nervous control (leading to so-called "central muscle fatigue"), when neuromuscular nervous control is unable to stimulate muscle fibers to their maximum capacity, or by alterations in contraction force at the direct level of muscle fibers (leading to so-called "peripheral muscle fatigue"). Within the framework of the present disclosure, the quantification method allows for the direct quantification of peripheral muscle fatigue in step (iii) if the electrical stimulation in step (i) directly affects peripheral muscle fibers independently of central nervous control of muscle contraction. Nevertheless, step (iii) can also optionally include a substep of quantifying central muscle fatigue by subtracting the quantified peripheral muscle fatigue from a separate global fatigue measurement. This differential quantification of muscle fatigue is novel in light of prior art methods.

[0021] Furthermore, 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, and the so-called "long-lasting peripheral muscle fatigue", which can be recovered from these factors quickly (within minutes), and which lasts for hours or even days (e.g., after physical effort). The peripheral muscle fatigue quantified in step (iii) is preferably, and more particularly, long-lasting peripheral muscle fatigue. Optionally, short-lasting peripheral muscle fatigue can also be quantified in step (iii) by additionally quantifying muscle fatigue at intervals of time following the method of the present disclosure and subtracting the obtained results.

[0022] Within the framework of the present disclosure, the term "electrical stimulation" and any of its variations preferably refers to electrical neuromuscular stimulation or any type of stimulation of the motor neurons of the muscle being tested. Such stimulation is preferably performed by a stimulator comprising a generator of electrical pulses and electrodes adapted to be placed on the subject's skin near and / or next to the muscle and connected to the generator so that an electrical current is transmitted to the muscle by the electrodes. The intensity and frequency of the electrical pulses can be adjusted. Such generators and electrodes are well known to those skilled in the art.

[0023] Preferably, the charge is defined by the electrical intensity of the pulse and / or by the (individual) pulse duration. In the following description of the disclosed subject matter, the charge is preferably defined only by the electrical intensity of the pulse. Nevertheless, this does not exclude other types of "charge" from the scope of the disclosed subject matter.

[0024] According to an embodiment, the electrical intensity for a given pulse duration is increased by 10 to 100 mA, and / or the number is comprised between 5 and 30, and / or the charging step is according to an increased intensity comprised between +0.1 and +10 mA. Preferably, these "and / or" are "and".

[0025] In this case, the constant pulses increase from a lower value to a higher value, both between 10 and 100 mA. Preferably, the lower value is between 10 and 40 mA, more preferably about 25 mA, so that the subject feels a very gentle first electrical stimulation. Preferably, the higher value is between 30 and 60 mA, more preferably about 40 mA, so as to avoid excessive muscle strain. Preferably, the number of times is between 10 and 20, more preferably about 15, so as to obtain a sufficient quantification (e.g., measurement) of muscle fatigue and, consequently, to minimize the error from the method. Preferably, the charging steps increase in intensity by +0.5 to +5 mA, more preferably about +1 mA, such a step value being sufficient to electrically stimulate muscle fibers that are sufficiently different from those when steps (i), (ii), and (iii) are performed once.

[0026] Preferably, the electrical intensity is increased from 25 to 40 mA in 15 charging steps of +1 mA. Such an increase in intensity allows each time to grow a new layer of muscle fibers that are not affected, and therefore not enhanced, by the electrical stimulation of the previous step (i). This makes the quantification method more accurate and easier to perform.

[0027] A similar increase in voltage has the same effect, or an increase in pulse width at a fixed current.

[0028] According to a representative embodiment of the present disclosure, a first rest period, preferably comprised between 100 ms and 10 s, is performed between two electrical stimulations at different frequencies in step (i). Preferably, the first rest period is comprised between 115 ms and 5 s, and more preferably, between 300 ms and 1 s.

[0029] The rest period between two electrical stimuli at different frequencies in step (i) makes it possible to mitigate or even avoid disturbances from one electrical stimulus to another, for example due to muscle rigidity.

[0030] The 10 second upper limit allows for a reasonable duration of total application time of the method. Preferably, the 5 second upper limit allows for rapid implementation of the method. Finally, the 1 second upper limit provides a balance between the duration of useful rest periods and the total application duration of the method.

[0031] The lower limit included between 100 ms and 115 ms allows for measuring force data at another frequency in step (i) that is sufficiently unaffected by the electrical stimulation at the previous frequency to estimate and / or quantify the maximum force in step (ii) with a certain error.

[0032] The lower limit comprised between 115 ms and 300 ms is preferred because it allows sufficient time for the muscle to return to a normal or relaxed state (in particular, no contraction or residual force exerted) between the electrical stimulations at the two different frequencies in step (i). This allows for a direct quantification of the (maximum) force exerted by the muscle at each of these frequencies without disturbance of the quantification. In particular, no estimation with sufficient error, nor intermediate measurements and / or calculations are required, as for a first rest period of less than 115 ms.

[0033] When a muscle has a certain level of muscle fatigue, a phenomenon described as "blunted relaxation" can occur. If present, this phenomenon prolongs the muscle's response from an electrical stimulus at one frequency to another electrical stimulus at another frequency in step (i), thus disturbing the measurement of the muscle's response to said another electrical stimulus at another frequency during step (i). Advantageously, even when this phenomenon occurs, a first rest period longer than 115 milliseconds allows for accurate quantification of the force exerted by the muscle in response to each electrical stimulus by applying any suitable mathematical or computer-implemented process configured to counteract the disturbance due to "blunted relaxation." Indeed, because this phenomenon is known, it can be predicted in certain measurements and taken into account in step (ii). An illustrative process to implement is simply linear interpolation of the expected disturbance and its removal from the measured force.

[0034] A lower limit of more than 300 milliseconds is nevertheless preferred because it always allows a full return to the normal and / or relaxed state of the muscle between two successive electrical stimuli in step (i), without disturbances affecting measurements of the muscle response caused by said electrical stimuli at another frequency.

[0035] Values ​​for the first rest period are 1 / 2, 3 / 5, 4 / 5, 1, 6 / 5, 7 / 5, 8 / 5, 9 / 5 seconds, etc. on the other hand, they are sufficiently far from any of the other lower limits, thus ensuring to avoid any potential disturbance of the force determination in step (ii) between two successive electrical stimuli in step (i), - and on the other hand, they are sufficiently short (on the scale of human sensations) so that the whole method is easily applicable in a sufficiently short time and in an overall short time. So it is preferred.

[0036] According to one embodiment, a second rest period is performed between two performances of step (i). The second rest period further reduces or avoids potentiation, since the number of electrical impulses per unit time is reduced when performing step (i) at separate intervals. Thus, the longer the duration between repeated stimulation episodes, the smaller the potentiation in muscle fibers caused by the stimulation episodes. However, similar to the first rest period, the second rest period should not last too long, in order to avoid the method becoming too slow to be applicable.

[0037] The inventors have determined a good compromise between these two conflicting constraints for defining the second rest period between two repetitions of step (i). Preferably, this period is comprised between 100 milliseconds and 5 minutes, thereby making it possible to limit the enhancement and the execution time of the method. A better range is given by the second rest period being comprised between 145 milliseconds and 10 seconds, more preferably between 330 milliseconds and 5 seconds. Since the magnitude of the enhancement depends on the number of electrical pulses delivered in a given time, the disclosed subject matter is advantageous for limiting the enhancement by reducing the number of pulses per unit time when repeating the steps.

[0038] The second rest period, lasting 145-330 milliseconds, allows sufficient time for the muscle to return to a normal or relaxed state (i.e., no contraction or residual force exerted) between two occurrences of step (i). This allows for direct quantification of the (maximum) force exerted by the muscle in response to each electrical stimulus without disturbance. In particular, no estimation with sufficient error, intermediate measurements, and / or calculations are required, which is not the case for the second rest period of 100-145 milliseconds. Even if a slowing of muscle relaxation occurs, a second rest period longer than 145 milliseconds allows for accurate quantification of the force exerted by the muscle in response to each electrical stimulus by applying any suitable mathematical or computer-implemented process configured to counteract disturbances due to "slowing of relaxation," as discussed above with respect to the first rest period. Naturally, in both cases, such a process is preferably part of step (ii).

[0039] A second rest period longer than 330 milliseconds is nevertheless preferred because it always allows the muscle to fully return to its normal and / or relaxed state between the end of performing step (i) and the beginning of the next performance of steps (i) through (iv), so that disturbances do not affect measurements of the muscle's response to electrical stimulation.

[0040] Values ​​such as 1, 2, 3, 4 or 5 seconds for the second rest period are highly preferred because, on the one hand, they are far enough away from any of the lower limit values ​​mentioned above, thus reliably avoiding disturbances in the force quantification in step (ii) between two successive performances of step (i), and, on the other hand, they are short enough (on the scale of human sensation) to make the implementation of the entire method sufficiently quick and easily applicable.

[0041] In short, these embodiments of the disclosed subject matter minimize potentiation so that measurements of muscle fatigue are accurate and not altered or underestimated by potentiation caused by electrical stimulation, which is even more significant when stimulation is repeated and the number of pulses is high.

[0042] Preferably, a first rest period is performed between two electrical stimulations at different frequencies in step (i), and the first rest period is shorter than a second rest period performed between two electrical stimulations of step (i). The second frequency is preferably higher than the first frequency, and the muscle response level is also higher at the second frequency. Therefore, it is preferable to wait a longer time after applying the electrical stimulation at the second frequency to ensure that the muscle response following the previous electrical stimulation is relaxed or even eliminated. For example, the first rest period is about 1 second, and the second rest period is about 5 seconds.

[0043] In one embodiment, in step (i), the electrical stimulation comprises repetition of pulses at each frequency for a time period of less than 5 seconds. Limiting the time for which the pulses are repeated mitigates the risk of voluntary or reflex disturbances in the subject, which could otherwise increase the force by adding electrically induced contractions, or conversely, decrease it by contracting antagonistic muscles to the electrically stimulated muscle. This makes the method more accurate and efficient.

[0044] Preferably, the pulse repetition time is shorter than 500 milliseconds. This shorter time, in addition to the aforementioned advantages, allows for a reduction in the total application time of the method, which further mitigates the risk of voluntary or reflex disturbance of the subject. The pulse repetition time is preferably shorter than 250 milliseconds, more preferably between 100 and 250 milliseconds. Preferably, the time is between 150 and 250 milliseconds, more preferably about 150+x milliseconds, for example, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, or 250 milliseconds, where x is an integer between 0 and 100.

[0045] Any of the above times less than 250 milliseconds may additionally: - on the other hand, reaching the maximum force generated by electrically induced contractions, and - on the other hand, that this maximum force is due exclusively to the electrically induced contraction, without any disturbances related to the voluntary or reflex responses of the subject. This makes it possible.

[0046] The absence of voluntary or reflex disturbances allows for accurate measurements of the force due solely to the electrically induced contraction. This accuracy in the recorded force therefore allows for a good measurement of muscle fatigue.

[0047] In other words, these advantageous times allow the muscle to be pulsed a certain number of times at each (selected) frequency, thereby allowing the maximum force exerted by the muscle in response to pulses at this frequency to be reached (and quantified in step (ii)) in a time short enough to avoid incurring muscle fatigue and / or the patient exerting any voluntary force.

[0048] These times found by the inventors are therefore a good compromise between the two conflicting constraints, the first of which requires a sufficiently long time, and the second of which requires a sufficiently short time.

[0049] 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), which indeed satisfies the formula T=N / μ.

[0050] Preferably, for each frequency, the pulses are repeated 2 to 50 times, and more preferably, for each frequency, the pulses are repeated 5 to 20 times. This range of repetition of the electrical stimulation pulses allows the maximum intensity to be reached, the recorded force to be maximized, and therefore, allows for accurate and precise measurement of the state of muscle fatigue.

[0051] According to one embodiment, the quantification method comprises, before step (i), a step of pre-stimulating the muscle with an isolated pulse, and a third rest period comprised between 100 milliseconds and 10 seconds is performed between this pre-stimulation step and step (i).

[0052] This optional isolated pulse is advantageous for measuring muscle data information such as the magnitude of the initial muscle response to the pulse, and / or contraction velocity, and / or pre-potentiation data, which may be used, for example, to tailor the electrical intensity of the pulse to the subject (or muscle), or generally to provide a more personalized performance of the method to the subject.

[0053] Preferably, while repetitions of step (iv) are applied, the pre-electrical stimulation step is repeated before each execution of step (i). This allows for continuous collection of such muscle data information during execution of the method and / or potentially for coordinating this execution. Alternatively, this pre-electrical stimulation step may be performed only once at the start of the entire execution of the method.

[0054] The third rest period is preferably similar to either the first or second rest period. The above discussion regarding either of these rest periods may apply to the third rest period. In particular, the third rest period is preferably about 1 second.

[0055] 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. Within this document, the terms "first", "second", "third", etc. are used only to distinguish elements and do not imply any order among these elements. Within 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 not limiting, and the fact that a first quantity is determined based on a second quantity does not exclude that the first quantity is also determined together with the first quantity based on a third quantity.

[0056] Within the framework of this document, the terms "smaller" or "lower than" and "greater" or "higher than" should be interpreted as the mathematical symbols "≦" and "≧", respectively. In addition, the use of the verbs "comprise", "include", "involve", or any other similar variations and their conjugations does not exclude the presence of elements other than those stated. When the verb "comprise" is used to define a numerical range by the term "comprised between" (two values), these two values ​​should not be interpreted as being excluded from the numerical range.

[0057] Within the framework of this document, the use of the terms "preferred," "preferably," "preferred," and the like 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 particularly, the inclusion of "preferred" ranges or embodiments in this disclosure is not intended to limit the scope of the claimed subject matter to include only "preferred" embodiments. In this regard, the inclusion of "preferred" embodiments should not be construed as expressing a disclaimer of subject matter not so identified.

[0058] Preferably, the frequency is between 0 and 1000 Hz, more preferably below 500 Hz, more preferably below 200 Hz. The frequency may be between 5 and 150 Hz. Such limits make it possible to avoid the induction of muscle fatigue by carrying out the quantification method.

[0059] According to a representative embodiment of the method for quantification, the frequency of step (i) is comprised between 0 and 500 Hz, preferably between 0 and 200 Hz; - a first frequency, and - a second frequency greater than the first frequency comprising (and possibly consisting of) The first frequency differs from the second frequency by at least 10% (in the sense that μ2−μ1≧μ2 / 10, where μ1 and μ2 are the first and second frequencies).

[0060] In this case, the forces quantified in step (ii) include 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. Each of these forces preferably corresponds to the maximum force exerted in response to all repetitions of pulses at the corresponding frequency (which repetition therefore constitutes one electrical stimulation at that frequency). A difference of at least 10% between the first and second frequencies is advantageous to ensure that at least two points on the aforementioned curve graph (the frequency used in step (i), the force quantified in step (ii)) are sufficiently separated from one another to perform step (iii) more efficiently. This makes it possible to take advantage of all the non-uniformity and non-linearity of the deformation of the curve graph as a function of muscle fatigue, if the force exerted by the muscle in response to electrical stimulation at low frequencies, for example 0-50 Hz, is more affected by pre-existing muscle fatigue than the force exerted by the muscle in response to electrical stimulation at high frequencies, as illustrated in Figure 2 presented below.

[0061] In particular, the difference is preferably at least 20%, more preferably at least 50%. 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. Any other similar value pairs for the first and second frequencies may be used, such as, for example, 10 Hz and 50 Hz, 30 Hz and 80 Hz, 50 Hz and 150 Hz, etc.

[0062] More preferably, according to the above embodiment, the different frequencies in step (i) consist of a first and a second frequency, and the forces quantified in step (ii) consist of a first and a second force. Advantageously, it is possible to quantify muscle fatigue in step (iii) only by considering these two (maximum) forces, as will be explained below.

[0063] 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 by considering only a limited number of data, the implementation of step (iii) is facilitated. The disclosed subject matter, however, is not limited to different frequencies consisting of only first and second frequencies. Numbers other than two frequencies are possible. By way of example, the different frequencies (and associated forces quantified in step (ii)) can be 3, 4, 5, 6, 7, 8, 9, 10, or more frequencies, which can also be equally spaced within the range of frequencies so that they are predetermined.

[0064] According to an illustrative embodiment of the present disclosure, the quantification method comprises, in step (i), In the time range of 100 to 250 milliseconds, - 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; and - 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. This is advantageous in order to have a certain number of repetitions of the electrical pulses that allows, on the one hand, to reach (and quantify) the maximum force generated by the electrically induced contraction, and, on the other hand, to ensure that this maximum force is exclusively due to the electrically induced contraction, without any disturbances related to the subject's voluntary or reflex responses. At the same time, this results in little or almost complete no strengthening of the muscle fibers of the muscle being tested (the different layers of the muscle being stimulated), making it possible to measure muscle fatigue effectively.

[0065] Preferably, in the context of a first frequency and a second frequency greater than the first frequency, step (iii) includes calculating a ratio of the first force to the second force, and muscle fatigue is quantified based on this ratio. More specifically and preferably, step (iii) also includes comparing the calculated ratio with a threshold value and quantifying muscle fatigue based on this comparison of the calculated ratio with the threshold value. This implementation of step (iii) is very simple and allows for a fast, low-complexity calculation for quantifying muscle fatigue. It is also very efficient. Indeed, as explained above, since the first frequency differs from the second frequency by at least 10%, the ratio is completely affected by the non-uniformity of the deformation of the curve graph in function of muscle fatigue. As a result, if the above-mentioned comparison makes it possible to identify a difference between the calculated ratio and a threshold value corresponding to the ratio expected for a non-fatigued muscle, such a difference represents muscle fatigue, and muscle fatigue can therefore be quantified at least implicitly, and preferably explicitly.

[0066] This embodiment of the present disclosure, and the term "based on" does not exclude step (iii), which also considers other information or calculations derived from the forces quantified in step (ii). For example, at least one other calculation for the other forces quantified in step (ii) can be used to quantify muscle fatigue, and step (iii) can include a sub-step for calculating an average value of the muscle fatigue thus quantified and comparing the calculated ratio with a threshold value, thereby enabling a more accurate and efficient quantification of muscle fatigue as an average value of such quantification. For example, this at least one other calculation can include calculating the ratio of the third force to the fourth force among the forces quantified in step (ii).

[0067] As a generalization of the previous embodiment of the present disclosure, step (iii) preferably includes comparing the forces determined in step (ii) and determining muscle fatigue based on the force comparison.

[0068] Said threshold value, which is compared with the ratio of the first force to the second force, preferably consists of the number F(μ) / F(μ′), where: F is a regular function that increases independently of the individual as a function of the frequency of this electrical stimulus, representing the force exerted by an unfatigued muscle in response to the electrical stimulus, μ and μ′ are the first and second frequencies, respectively. In other words, in this case, F is preferably a theoretical function known to those skilled in the art that underlies a family of thresholds of the formula F(μ) / F(μ′) that can be used to define the threshold.

[0069] 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 does not limit the scope of the disclosed subject matter. For the above-described examples including only first and second frequencies, it is not necessary to consider the entire function F, as the numerical values ​​corresponding to these frequencies are sufficient.

[0070] In the context of calculating the ratio between frequencies and comparing it to a threshold, the first frequency may preferably be comprised between 10 and 40 Hz; and / or The second frequency may preferably be comprised between 90 and 130 Hz. In this case, the threshold value is preferably between 40 and 90%. More preferably, the first frequency is about 20 Hz, the second frequency is about 120 Hz, and the threshold value is about 60%, 65%, 70%, 75%, or 80%. Such a combination of values ​​makes it very easy and efficient to implement the quantification method of the disclosed subject matter in the context of a first frequency and a second frequency greater than the first frequency. It does not clearly limit the scope of the disclosed subject matter, and other values ​​are possible.

[0071] Within the framework of this document, the terms "quantifying", "quantifying", "quantification" and any other variations preferably correspond to the terms "quantifying", "quantifying" and "quantifying" 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 a calculated ratio with 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 force quantified in step (ii), such as, for example, an associated rotational force. Conversely, the scope of step (ii) does not exclude the quantification of muscle fatigue based on intermediate physical quantities related to the force that can be measured in response to the electrical stimulation of step (i), such as, for example, a displacement, acceleration and / or rotational force.

[0072] According to another embodiment of the quantification method disclosed herein, the frequencies include a minimum frequency less than 50 Hz and a family of frequencies less than 200 Hz that are integer multiples of the minimum frequency. This family more preferably includes all frequencies less than 150 Hz that are integer multiples of the minimum frequency. In other words, in this case, the frequencies in the family are equally spaced. Although this embodiment requires more electrical stimuli in step (i), this embodiment is advantageous because it allows for the acquisition of more data on which a wide variety of points (frequencies used in step (i), forces quantified in step (ii)) can be based, at least some of which are uniformly distributed at least locally, and preferably globally, on the curve graph, for efficient and accurate execution of step (iii). Such a family may consist, for example, of {5nHz|1≦n≦30, n integer}={5Hz, 10Hz, 15Hz, . . . , 150Hz} if 5Hz is the minimum frequency, or {30Hz, 60Hz, 90Hz, 120Hz} if 30Hz is the minimum frequency. A family may also consist, for example, of {10Hz, 20Hz, 30Hz, 40Hz, 100Hz, 110Hz, 120Hz, 130Hz} if 10Hz is the minimum frequency; thus, not all frequencies that are integer multiples of 10Hz are included in the family.

[0073] Preferably, according to the previous embodiment of the method, step (iii) comprises: - for each frequency of the family, calculation of the discrete integral of the (discrete) function related to the force determined in step (ii) exerted by the muscle in response to the electrical stimulation of step (i) at this frequency; and - Quantification of muscle fatigue based on calculated discrete integrals Includes:

[0074] This discrete integral typically corresponds to a Riemann sum. It is preferably implemented efficiently when the family includes all integer multiples of a minimum frequency less than 150 Hz, which is preferably less than 20 Hz, more preferably less than 10 Hz, for good calculation accuracy. Preferably, step (iii) includes comparing the calculated discrete integral with the value of a certain region and quantifying muscle fatigue based on the comparison of the calculated discrete integral with the value of that region. The value of this region is preferably the value of the region under the graph of the aforementioned function F. As is well known in sum-difference physics, the comparison makes it possible to evaluate the difference between this theoretical region for an unfatigued muscle and its approximation by a Riemann sum for the muscle, and to quantify muscle fatigue based thereon in an accurate manner due to the number of frequencies in the family and the preferred overall uniform distribution. Optionally, different frequencies are comprised in this family of frequencies.

[0075] The embodiment of the preceding paragraph is compatible with various other preceding embodiments. In particular, as explained, it is possible to consider the quantification of muscle fatigue in step (iii) based on the calculated ratio between the first and second frequencies and on said calculated discrete integral, for example by an averaged comparison of said calculated ratio and said calculated discrete integral with an expected normal value independent of the individual for a fatigue-free muscle. In this case, the first and second frequencies may also belong to the family.

[0076] According to another disclosed embodiment of the method, the forces are quantified in step (ii) by direct force measurements, preferably by strain gauges or dynamometers. In particular, the quantification of forces in step (ii) is performed directly by appropriate techniques and by measuring the forces (in Newtons), without relying on intermediate or indirect measurements and / or observations (such as by electromyography), nor on estimations or evaluations that introduce a risk of error in step (ii). These direct force measurements are preferably performed by novel dedicated devices, which are presented hereinafter as part of the system.

[0077] Preferably, the muscles involved comprise muscles of the human lower limb. Preferably, the muscles comprise the quadriceps or hamstrings. In either of these cases, according to exemplary embodiments of the present disclosure, the method further comprises, prior to step (i), the following steps: (a) a seat adapted to receive a person in a seated position and to be positioned on a horizontal support; a leg support element mechanically coupled to the seat and adapted to receive at least a portion of the leg of the lower leg; Instruments for measuring the forces (mentioned above) at the level of the leg support element providing an apparatus comprising: (b) positioning the seat on a horizontal support; (c) positioning the person on the seat in a seated position; and (d) positioning at least a portion of the leg on the leg support element; Includes:

[0078] Preferably, the force is quantified by this instrument in step (ii). This device is advantageously very simple and easy to move, while allowing for accurate quantification of the force in step (ii). The process for performing step (i) is also very simple, since when a person sits on the seat, their legs are positioned on the leg support elements, which allow them to maintain a stable position. Preferably, the person's weight, acting at the level of the seat, simply allows the device to be maintained substantially stationary relative to the horizontal support during the performance of steps (i) and (ii). In particular, no complex structure is required to receive the person and perform the method. A simple plane connected to the leg support elements is used as the seat and can be positioned anywhere on a horizontal support, such as a platform or another seat. The device is described in more detail below as part of a muscle fatigue quantification system.

[0079] Preferably, steps (c) and (d) above comprise: the feet 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 It's like this.

[0080] Advantageously, the seat is the only contact point for the lower limbs (thighs at the front level of the seat and knees at the side level of the seat), which makes it possible to fully understand the conditions for measuring the forces in step (ii) and to avoid any measurement disturbances that may be induced by forces exerted by the feet on the support, e.g., the ground. Preferably, the person is positioned in steps (b) and (c) so that their back is upright and forms a substantially right angle with the thighs of the lower limbs. Due to the simple structure of the device and the ease of positioning the person, the force measurements by the instrument are reproducible. This would be highly advantageous for the purpose of applying the disclosed method of quantification if the muscle fatigue quantified in step (iii) could be compared at any time and anywhere throughout the day, provided that the seat can be positioned on a horizontal support without having to perform the method in the same place and under the same conditions, and without having to worry about variations in parameters related to the person's positioning.

[0081] It is preferred to implement the quantification method according to the present disclosure in a system that allows for efficient quantification of muscle fatigue without inducing muscle fatigue itself, at any time regardless of the subject's will, and without exposing the subject to risk of injury.

[0082] To this end, such a system for implementing the method for quantifying muscle fatigue preferably comprises: for generating electrical stimulation of muscles at a range of frequencies, and any frequency of electrical stimulation within the frequency range, and / or any charge, preferably the electrical intensity of the pulse, and / or ○ Any number of pulses, and / or any number of repetitions of a pulse in a period of time, or any such period of time, and / or any first and / or second and / or third rest periods between the electrical stimulations at different frequencies in step (i) and / or between successive performances of step (i) and / or between the pre-electrical stimulation step and step (i), respectively, as explained above in connection with the method; an apparatus comprising a control device for selecting A device for quantifying the force exerted by a muscle in response to an electrical stimulus generated by the device; and a logic unit coupled to the device and configured to determine muscle fatigue based on forces determined by the device as forces exerted by the muscle in response to electrical stimuli generated by the device at different frequencies within the range of frequencies; Equipped with.

[0083] The device, and more particularly the control device, is also preferably configured to select and / or modify (in particular increase) the charge, preferably the electrical intensity of the pulse, between two occurrences of step (i), at a particular charging step as described above. In accordance with the above related embodiment of the method, the control device preferably allows selection of any charge-related parameters, such as the electrical intensity of the pulse, and / or the pulse duration, and / or the number of repetitions of steps (i)-(iii) performed in step (iv), and / or the charging step between two occurrences of step (i). More preferably, the control device may be programmed to implement a charge program associated with the method to replicate the charge escalation and / or frequency selection associated with the electrical stimulation as described above.

[0084] The above-described system allows for carrying out the quantification method according to the present disclosure, preferably wherein step (i) is performed by an instrument, step (ii) is performed by an apparatus, and / or step (iii) is performed by a logic unit.

[0085] All embodiments of the quantification method according to the present disclosure, and the advantages of these embodiments, apply mutatis mutandis to the present system according to the present disclosure, which is in particular an efficient, safe and adaptable system for quantifying muscle fatigue.

[0086] Preferably, the range of frequencies spans at least any of the above numerical ranges of frequencies. Preferably, it spans from 0 to 200 Hz. According to an exemplary embodiment of the system, the logic unit: a first force quantified by the device as a force exerted by the muscle in response to a first electrical stimulus generated by the device at a first frequency within the range of frequencies; and - a second force quantified by the device as a force exerted by the muscle in response to a second electrical stimulus generated by the device at a second frequency within the range of frequencies; the first frequency is lower than the second frequency and differs from the latter by at least 10%; performing calculations for at least some of the forces; Quantify muscle fatigue based on this calculation It is configured as follows. Such calculation and quantification of muscle fatigue may be performed as previously described.

[0087] According to an embodiment of the system, the device comprises at least one strain gauge or force gauge for directly measuring the forces exerted by the muscles in response to the electrical stimuli generated by the equipment. Advantageously, the device thus allows direct force quantification by appropriate instruments and by making these forces (in Newtons) a direct measurement, without relying on intermediate or indirect measurements and / or observations, nor on estimations or evaluations which introduce a higher risk of error in the force quantification.

[0088] According to an exemplary embodiment of the system, in which the muscles of a person's lower limbs are adapted to be the muscles in question, the device is itself a novel, dedicated device for quantifying any force exerted by the muscles in response to electrical stimuli generated by the device. This device has already been partially described. It is a seat adapted to receive a person in a seated position and to be positioned on a horizontal support; a leg support element mechanically coupled to the seat and adapted to receive at least a portion of a leg of the lower extremity; and An instrument for measuring the force exerted by the muscles at the level of the leg support element in response to electrical stimulation generated by the device. Equipped with.

[0089] The device is configured to be maintained substantially stationary relative to a horizontal support when, due to the weight of the person acting at the level of the seat, forces are exerted by muscles at the level of the leg support elements in response to electrical stimuli generated by the equipment at different frequencies.

[0090] The advantages of this embodiment of the system were discussed above. The device is designed to be used without a supervisory operator and has a stable, robust structure, so that force measurements are accurate and reproducible. In particular, the device is simple and lightweight. The device preferably does not have a backrest or legs associated with the seat, so that the seat is substantially flat and can be positioned on any horizontal support, such as a table or another seat. The device is therefore easily transportable, allowing force measurements to be taken wherever a person is, without the need for additional equipment or structure. In particular, a person does not need to travel to a specific medical or sports facility to quantify muscle fatigue. The seat is sufficiently wide to fully accommodate a person seated on it. It preferably extends continuously along two vertical axes, at least 40 cm, preferably at least 50 cm, or at least 60 cm.

[0091] 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 includes a semi-cylindrical hollow portion to match the curvature of the leg portion and immobilize it laterally. The leg support element may also include a strap to better immobilize the leg portion.

[0092] The gauge is preferably attached (not intermediately, or in other words directly) to a part that is (arranged to be) aligned with the direction of said force, especially in the configuration in use of the device. This gauge is preferably aligned with the leg support element. In both cases, it allows for easy, direct and very accurate force measurement. It may preferably be part of a single part with the leg support element, or in other words, it is preferably fixed to the leg support element. The gauge may consist of a strain gauge or a force gauge as described above, which can be arranged on the device to operate in traction or in compression, so that reproducible, direct and accurate measurements of force can be made.

[0093] Preferably, the leg support element of the device is (mechanically) connected to the seat by a mechanical arm or a mechanical frame. Preferably, the latter comprises a connection member to the instrument at the level of the seat or at the level of the leg support element. 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 preferably comprises at least one higher extremity connected to (or fixed with) the seat and at least one lower extremity connected to (or fixed with) the leg support element.

[0094] Optionally, the device also comprises: - the position and / or orientation of the mechanical arm or mechanical frame relative to the seat; - the position and / or orientation of the leg support element relative to the mechanical arm or mechanical frame; and at least one position adjustment element for modifying at least one of the above. Such a positioning element may preferably comprise any mechanical element known to those skilled in the art, such as a screw, bolt, pin, spring, or the like, configured to cooperate with the mechanical arm or frame, for example within a cavity. Preferably, when the mechanical arm or frame is a simply shaped mechanical arm, it comprises such a positioning element for orienting the leg support element in one of two opposing directions along a direction (or line) perpendicular to the mechanical arm, where one of these directions is adjusted to properly orient the leg support element to receive the leg portion of a person's right lower limb, and the other of these directions is adjusted to properly orient the leg support element to receive the leg portion of a person's left lower limb. When the mechanical arm or frame is a frame, it preferably comprises such a positioning element for properly positioning the leg support element along the side of the frame to properly receive the leg portion of a person's right or left lower limb. The structure of the device is therefore simple and is adjusted to the lower limb to which the muscle whose muscle fatigue needs to be quantified belongs.

[0095] More specifically, the device of the system preferably consists only of a seat, leg support elements, a scale, a mechanical arm or mechanical frame, and, if included, any position adjustment elements, which are therefore simplified to a very simple and practical form, but which allows to carry out step (ii) of the quantification method in a very satisfactory manner for quantifying muscle fatigue.

[0096] The disclosed subject matter is further presented in the claims. As will be understood by one skilled in the art from this disclosure, any one of the embodiments presented in the claims can be considered alone or in combination. The dependency of the claims can be considered in a broader manner, so that any one of the possible combinations of the claims is part of this application, as long as they are technically possible and understood by a person skilled in the art, especially in view of this disclosure.

[0097] 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 should be made to the accompanying drawings. [Brief explanation of the drawings]

[0098] [Figure 1] 1 is a flow diagram of a quantification method according to an exemplary embodiment of the present disclosure. [Figure 2] 1 is a curve graph of the (total and / or maximum) force exerted by a muscle in response to electrical stimulation at a given frequency as a function of this frequency. [Figure 3] FIG. 1 illustrates an example system for implementing an exemplary embodiment of the disclosed muscle fatigue quantification method. [Figure 4] 1 is a schematic experimental curve graph of force measured as a function of time during a method according to an exemplary embodiment of the present disclosure; DETAILED DESCRIPTION OF THE INVENTION

[0099] 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 should not be considered limiting, especially when these numbers appear in the claims.

[0100] A description of exemplary embodiments of the disclosed subject matter is given below with reference to the 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.

[0101] As shown in FIG. 1, the exemplified muscle fatigue quantification method involves applying electrical stimulation to different frequencies μ, μ, μ, μ, . . . μ for a number n of electrical stimulations, e.g., 2≦n≦50, preferably 2≦n≦5. n The muscles are electrically stimulated with the frequencies μ1, μ2, μ3, μ nThe respective (maximum) forces F1, F2, F3, ..., F exerted by the muscles in response to each of the electrical stimuli at n and determining, preferably measuring, the forces F1, F2, F3, . . . , F n Such determination may be performed, for example, by a ratio calculation and / or a discrete integral calculation of two forces and a comparison of at least one of these calculations with at least one expected value, as fully described above.

[0102] Figure 2 illustrates a graph of the (maximum) force exerted by a muscle in response to an electrical stimulus as a function of frequency. Force is read on the vertical axis 82 (in Newtons) and frequency is read on the horizontal axis 81 (in Hertz). Curve graph 61 corresponds to a graph of a theoretically expected function F, representing the force exerted by an unfatigued muscle in response to an electrical stimulus as a function of the frequency of such a stimulus. Curve graph 62 shows the force exerted by a muscle at points (μ1, F1), (μ2, F2), (μ3, F3), ..., (μ n ,F n ) shows a continuous and regular spread of dots cloud corresponding to the muscle's force. It is noted that the interval between the two curve graphs 61 and 62 is larger for low frequencies (e.g., 10-40 Hz) than for 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 high frequencies.

[0103] If it is assumed that the ratio F(20) / F(120) is known to be approximately 60%, it is therefore sufficient to measure the forces F1 and F2 exerted by the muscle in response to electrical stimulation at μ1=20 Hz and μ2=120 Hz, respectively, to quantify muscle fatigue, advantageously without the need to identify an individual-independent curve graph for the same but unfatigued muscle.

[0104] In fact, since F2 corresponds substantially to F(120), the measurement of F2 corresponds in some sense to the reference measurement, and the measurement of F1 makes it possible to clearly express deviations from the expected value in terms of a ratio to F2.

[0105] In particular, muscle fatigue can be considered to be quantified by the method and quantified when the ratio F1 / F2 is significantly different from 65%. This value of approximately 65% ​​for the ratio is illustrative and not limiting. Other values ​​such as approximately 60%, or approximately 70%, or approximately 80%, may be advantageous depending on the function F under consideration. Likewise, these values ​​of μ1 and μ2 are in no way limiting. For example, the exact same argument could be true with μ2=100 Hz instead of 120 Hz.

[0106] For the muscles of the lower limbs, forces F1, F2, F3, ..., F nAn advantageous device 1 for measuring muscle fatigue is illustrated in FIG. 3. The device is advantageous for implementing a muscle fatigue quantification method. The device 1 comprises a seat 10 having a smooth portion 11 for receiving a person in a seated position, a rigid frame 12 for the smooth portion 11, and a positioning lower member 13 for removably positioning the seat on a horizontal support. The rigid frame 12 contributes to the rigidity of the seat, particularly at the level of the smooth portion 11, which may be made of a soft and / or padded material for the person's comfort. The positioning lower member 13 may be height-adjustable below the smooth portion 11 from 0 to 1 / 20 meter 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, as other parts of the device 1 extend lower than them.

[0107] The device 1, as illustrated, comprises a leg support element 3 fixed to a seat 10 by a mechanical frame 2. The leg support element 3 comprises a semi-cylindrical hollow portion for receiving and at least partially immobilizing the lower part of the leg of the lower limb. It integrates an instrument 4 for measuring the force exerted by the muscles at the level of the leg support element 3, in particular in response to an electrical stimulus. The mechanical frame 2 comprises a connection member 5 to the instrument 4 at the level of the leg support element. In particular, in the illustrated configuration of FIG. 3 , the instrument 4 is a strain gauge sandwiched between the leg support element 3 and the connection member 5 and fixed along a first direction. The strain gauge comprises a connection tip 41 for connecting the device 1 to a logic unit (not shown) of the disclosed quantification system. The logic unit is configured to measure the frequencies μ1, μ2, μ3, . . . μ n Forces F1, F2, F3, . . . , F are quantified by apparatus 1 in response to electrical stimulation at each of n The method is configured to quantify muscle fatigue based on at least some of the following:

[0108] The connecting member 5 also comprises a position adjusting element 51 for changing the position of the leg support element 3 and the instrument 4 relative to the mechanical frame 2 along a second direction d which is perpendicular to the above-mentioned first direction.

[0109] Implementation of a method according to an exemplary embodiment of the disclosed subject matter comprises the following steps: For a given initial electrical strength comprised between 10 and 50 mA, preferably (approximately) 25 mA, For a given charging step S comprised between 0.1 and 10 mA, preferably (approximately) 1 mA, and successively, for each integer k (the so-called "number of times") from 0 to K, where K is comprised between 5 and 30, and preferably is (approximately) 15: - electrically stimulating the muscle at a first frequency μ1 (preferentially (approximately) 20 Hz) with a repetition of N1 pulses for a time T1 shorter than 250 milliseconds, the pulses having a constant duration and intensity I0+kS, - quantifying the (maximal) force F1 exerted by the muscle in response to this electrical stimulation; - waiting for a first rest period R1 comprised between 300 milliseconds and 5 seconds, preferably (approximately) 1 second, - electrically stimulating the muscle at a second frequency μ (preferentially (approximately) 120 Hz) with a repetition of N pulses for a time T shorter than 250 milliseconds, the pulses having a constant duration and intensity I+kS, - quantifying the (maximal) force F2 exerted by the muscle in response to this previous electrical stimulation; - determining at least one muscle data information, preferably muscle fatigue of a muscle, based on the determined forces F1 and F2; - waiting during a second rest period R2 comprised between 330 ms and 10 s, preferably (approximately) 5 s; Includes:

[0110] It may be noted that the equations T1 = N1 / μ1 and T2 = N2 / μ2 represent the relationship between the number of pulses, the duration of electrical stimulation, and the frequency of electrical stimulation. In particular, N1 is preferably (approximately) 5 when μ1 is (approximately) 20 Hz, and N2 is (approximately) 18 when μ2 is (approximately) 120 Hz. These numbers of pulses allow the maximum forces F1 and F2 to be reached and allow the number of electrical stimulations T1 and T2 to be limited to 250 milliseconds to avoid any disturbance in the force measurement. For example, if N2 is considered to be 25, T2 is still less than 250 milliseconds, but the (maximum) force F2 remains substantially unchanged compared to that for N2 of 18. These values ​​of N1 and N2 were experimentally derived by the inventors as a preferred embodiment of the present disclosure, particularly in conjunction with the above-mentioned values ​​of μ1 and μ2.

[0111] 4 illustrates a purely schematic curve graph 63 of the (contraction) force exerted by the muscles of a person's lower limbs as a function of time during a partial execution of a method according to a representative embodiment of the present disclosure. In particular, this figure illustrates the effect of electrical stimulation for any k, thus including the entire execution of step (i). It can easily be derived that the curve graph repeats itself similarly for each execution of step (i), i.e., for each k, after a second rest period R2. The symbols T1, R1, F1, T2, R2, F2 presented above apply equally to FIG. 4.

[0112] The graph in FIG. 4 differs from that in FIG. 2 in that it represents only the maximum force determined in step (ii) for each frequency. The curve graph 63 is reproduced in a schematic manner based on experimental measurements. The measured force (e.g., by a strain gauge) is still read on the vertical axis 82 (in Newtons), while the horizontal axis 83 now indicates time. FIG. 4 is schematic and does not show explicit experimental data. The axes are not necessarily given in linear scale. In particular, for clarity, the times N1 and N2 corresponding to the example in FIG. 4 are 3 and 5, respectively, and the times T1, R1, T2, and R2 marked on the axes 83 are not evenly scaled.

[0113] It can be seen in Figure 4 that the muscle is electrically stimulated with a first frequency μ1 in a repetition of three pulses at a time T1 shorter than 250 milliseconds, with the pulses having a constant duration and intensity I0 + kS. Each pulse occurrence corresponds to a scale line 84 on the time axis 83. The effect of the pulses on the curve graph 63 is marked by 64 and is clearly visible as a gradual increase in the force exerted by the muscle due to its contraction and, therefore, its tetanization process. In other words, the pulses generated at 84 are sufficiently close together that a kind of fusion of the effect on the muscle of each individual pulse is observed along the time T1, thus resulting in such a stepped portion of the curve graph 63 at the time T1.

[0114] The same considerations apply to the electrical stimulation of the muscle in step (i) at a second frequency μ > μ with a repetition of 5 pulses for a time T shorter than 250 milliseconds, the pulses having the same constant duration and intensity I + kS.

[0115] Each of these electrical stimuli at frequencies μ1 and μ2 at respective times T1 and T2 allows for the reaching and quantification of the maximum force F1 and F2, respectively, exerted by the muscle in response to the electrical stimuli, as visible on axis 82 in FIG. 4, and subsequent quantification of muscle fatigue in step (iii). As visible in FIG. 4, the first and second rest periods R1 and R2 are long enough to allow the muscle to fully return to a "normal" and / or "relaxed" state without any contraction due to the previous electrical stimuli, any residual force exerted, and any of these before the start of the next electrical stimuli. In other words, the rest periods R1 and R2 allow the curve graph 63 to return to the baseline. The rest period R1 occurs between electrical stimuli at frequencies μ1 and μ2 with the same pulse intensity of the formula I0 + kS. The rest period R2 occurs between electrical stimuli at frequency μ2 with pulse intensity I0 + kS and electrical stimuli at frequency μ1 with pulse intensity I0 + (k+1)S.

[0116] As broadly described in this disclosure, this method is advantageous for avoiding disturbance effects on the quantification of forces F1 and F2. Figure 4 also illustrates, by dotted lines, examples of the effects of such disturbances 91, 92, and 93 on curve graph 63. They are purely fictitious, as the method is specifically designed to avoid them.

[0117] Disturbance 91 shows an example of a tetanic effect on curve graph 63 due to failure to adhere to the lower limit discussed above for the first rest period R1. If this period is not sufficiently sustained, the muscle will still be contracted and not relaxed when the next electrical stimulation begins, thereby affecting the measurement of F2, which will be excessively high due to partial (tetanic) fusion of the effects of the electrical stimulation at frequencies μ1 and μ2. In cases where fusion is partial and very limited (i.e., for R1 greater than 115 ms), it is nevertheless possible to apply straightforward mathematical processing (e.g., by linear interpolation) to quantify force F2 from the observed disturbed curve graph 91. Similar considerations obviously apply to the second rest period R2.

[0118] Disturbance 92 shows an example of an enhancing effect on curve graph 63 over time T1 (though one skilled in the art will readily understand that such an effect is not limited to this time). By not increasing the pulse intensity of charging step S during successive performances of step (i), the muscle is enhanced, so that the actual force F1 is disturbed, particularly greater than it should be, due to some training of the muscle fibers. Increasing the intensity during successive performances of step (i) according to the present disclosure makes it possible to avoid such an enhancing effect.

[0119] Finally, disturbances 93 represent instances of voluntary and / or reflex muscle contractions by the subject in parallel with the electrical stimulation. The subject increases force during the pulse and decreases it between or after the pulse. Advantageously, such disturbances do not occur if times T1 and T2 are so short (maximum 250 milliseconds) that the subject is unable to react on his or her own during the electrical stimulation.

[0120] It will be readily understood by those skilled in the art that the number of electrical stimuli n for the class of examples is equal to 2, but that these examples can be easily generalized to any number n>1.

[0121] In other words, the present disclosure relates to a method for quantifying muscle fatigue based on information derived from the forces exerted by a muscle in response to electrical stimulation of the muscle at different frequencies, where the steps of the method are repeated with increasing charge of the electrical stimulation.

[0122] The disclosed subject matter has been described in connection with specific examples that have utility that is 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. The examples and advantages of the quantification 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: (i) electrically stimulating said muscle with a given charge at different frequencies by an electrical stimulation generating device; (ii) measuring with a quantification device the force exerted by said muscle in response to said electrical stimulation of step (i); (iii) collecting, by a logic unit, data relating to muscle fatigue based on the forces measured in step (ii); and (iv) repeating steps (i), (ii), and (iii) a number of times with increasing charge, wherein the charge in step (i) is increased by a charging step between two occurrences of step (i). A method comprising:

2. 10. The method of claim 1, wherein the electrical stimulation comprises a repetition of pulses at each frequency, and the charge is determined by one of the electrical intensity of the pulse and the duration of the pulse.

3. 3. The method of claim 2, wherein the electrical intensity for a constant pulse duration is increased from 10 to 100 mA, the number of times is 5 to 30, and the charging steps are at increasing intensity from +0.1 to +10 mA.

4. 4. The method of claim 3, wherein the electrical intensity is increased from 25 to 40 mA in 15 charging steps of +1 mA.

5. 5. The method according to claim 1, wherein a first rest period comprised between 100 milliseconds and 10 seconds occurs between two electrical stimulations at different frequencies in step (i).

6. 6. The method of claim 5, wherein the first rest period has a duration of 115 milliseconds to 5 seconds.

7. 7. The method of claim 5 or 6, wherein a second rest period occurs between two occurrences of step (i), and the duration of the first rest period is shorter than the duration of the second rest period.

8. 8. The method of claim 7, wherein the duration of the second rest period is between 100 milliseconds and 5 minutes.

9. 9. The method of claim 8, wherein the duration of the second rest period is between 145 milliseconds and 10 seconds.

10. 10. The method of claim 1, wherein the electrical stimulation comprises repetition of pulses at each frequency for a period of less than 5 seconds.

11. The method of claim 10 , wherein the period is less than 500 milliseconds.

12. 12. The method of any one of claims 1 to 11, wherein the electrical stimulation comprises pulses repeated 2 to 50 times at each frequency.

13. 13. The method of any one of claims 1 to 12, comprising a pre-electrical stimulation step of the muscle with isolation pulses prior to step (i), wherein a third rest period having a duration of 100 milliseconds to 10 seconds occurs between this pre-electrical stimulation step and step (i).

14. the frequencies in step (i) are between 0 and 500 Hz and include a first frequency and a second frequency greater than the first frequency, the first frequency differing from the second frequency by at least 10%; 14. The method of any one of claims 1 to 13, wherein the forces comprise a first force exerted by the muscle in response to the electrical stimulation of step (i) at the first frequency, and a second force exerted by the muscle in response to the electrical stimulation of step (i) at the second frequency.

15. 15. The method of claim 14, wherein the first frequency is between 0 and 50 Hz and the second frequency is between 50 and 200 Hz.

16. step (i), during a period of 100 to 250 milliseconds, - electrically stimulating the muscle with a repetition of 3, 4, 5, or 6 pulses at the first frequency of 10, 15, 20, or 25 Hz; and - electrically stimulating the muscle with a repetition of 16, 17, 18, or 19 pulses at the second frequency of 100, 110, 120, or 130 Hz.

16. The method of claim 15, comprising:

17. 17. The method of claim 1, wherein step (iii) comprises comparing the forces measured in step (ii) and collecting data regarding the muscle fatigue based on the comparison of the forces.

18. 17. The method of any one of claims 14 to 16, wherein step (iii) comprises calculating a ratio of the first force to the second force, comparing the calculated ratio to a threshold value, and collecting data regarding the muscle fatigue based on this comparison of the calculated ratio to the threshold value.

19. 19. The method of any one of claims 1 to 18, wherein the force is measured in step (ii) by direct force measurement with at least one of a strain gauge and a dynamometer.

20. Before step (i), (a) providing an apparatus (1), the apparatus (1) comprising: a seat (10) configured to receive a person in a seated position and adapted to be positioned on a horizontal support; a leg support element (3) mechanically connected to said seat (10) and adapted to receive at least a portion of a leg of a lower limb; said quantifying device (4) configured to measure said force at the level of said leg support element (3); comprising the steps of: (b) positioning the seat (10) on the horizontal support; (c) positioning the person on the seat (10) in a sitting position; and (d) positioning at least a portion of said leg on said leg support element (3); Including, 20. The method according to any one of claims 1 to 19, wherein the force is measured by the quantitative device (4) in step (ii) and the device (1) is kept substantially stationary relative to the horizontal support during the execution of steps (i) and (ii) depending on the weight of the person acting at the level of the seat (10).

21. 1. A method for planning a sporting activity, comprising: (0) identifying muscles stimulated during the sports activity; (1) performing the method of any one of claims 1 to 20 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); A method comprising:

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