Method for evaluating fatigue, and kit and system for evaluating fatigue

Abstract

The present disclosure provides a means for noninvasively evaluating fatigue for purposes such as designing training intensity and evaluating training effects. A method for evaluating fatigue of a subject being tested according to the present disclosure is characterized in that a measurement step for measuring a concentration of lactic acid in tear fluid collected from the subject being tested is included, and that the concentration of the lactic acid in the tear fluid is an index for evaluating fatigue of the subject being tested. The present disclosure further relates to a tear-inducing component generation kit for use in the method for evaluating fatigue of a subject being tested, the tear-inducing component generation kit comprising LFS, alliinase, and PRENCSO. The present disclosure further relates to a system for evaluating fatigue of a subject being tested in which a measured value of a concentration of lactic acid in tear fluid of the subject being tested is compared with a reference value to determine information related to a degree of fatigue of the subject being tested.

Description

Method for assessing fatigue, and kit and system for assessing fatigue

[0001] The present disclosure relates to methods for assessing fatigue in a subject, such as a human, as well as kits and systems for assessing fatigue.

[0002] One of the energy supply systems for muscles during physical exercise in living organisms such as humans is the glycolytic pathway, which generates energy using carbohydrates such as glycogen as a substrate.

[0003] Because lactic acid is produced when energy is supplied by glycolysis, blood lactate concentration increases as the exercise intensity increases. The exercise intensity at which blood lactate concentration begins to increase rapidly is called the lactate threshold, and is used as a guideline for setting training intensity and understanding the effects of training.

[0004] Measurement of blood lactate concentration requires invasive blood sampling (see Non-Patent Document 1), which is physically and mentally painful. Furthermore, if hygiene management during blood sampling is insufficient, there is a risk of contracting an infectious disease.

[0005] For this reason, methods to measure lactate concentration in sweat or on the skin surface are being considered as non-invasive alternative methods to measuring blood lactate concentration. However, methods to measure lactate concentration in sweat cannot be used in environments where sweat cannot be collected. Furthermore, measuring lactate concentration on the skin surface is still at the research level and cannot be considered a reliable evaluation method.

[0006] Japanese Patent Application Laid-Open No. 2008-285476

[0007] Arkray website (URL: https: / / biz.arkray.co.jp / lact / confirm / introduction.html) International Ophthalmology Clinics 40(4): pp. 113-122, Fall 2000

[0008] An object of the present invention is to provide a means for non-invasively assessing fatigue.

[0009] The present inventors discovered that the concentration of lactic acid in tears, which can be collected non-invasively, correlates with the degree of fatigue of a subject and can be used as an index for assessing fatigue, leading to the completion of the following invention.

[0010] [1] A method for evaluating fatigue in a subject, comprising a measuring step of measuring the concentration of lactic acid in tears collected from the subject, wherein the concentration of lactic acid in the tears is an index for evaluating fatigue in the subject.

[0011] [2] The method according to [1], further comprising an evaluation step of evaluating fatigue of the subject based on the concentration of lactic acid in the tear fluid.

[0012] [3] The method according to [1] or [2], wherein the tear fluid is collected from the subject during or after physical exercise.

[0013] [4] The method according to any one of [1] to [3], further comprising a collection step of collecting the lacrimal fluid from the test subject, the collection step comprising: contacting the eye of the test subject with a lacrimal fluid generated by mixing LFS (lacrimatory component generating enzyme), alliinase, and PRENCESO (S-1-propenylcysteine ​​sulfoxide) to stimulate the secretion of the lacrimal fluid; and collecting the secreted lacrimal fluid.

[0014] [5] The method according to any one of [1] to [4], wherein the tear fluid is isolated from the subject.

[0015] [6] The method according to any one of [1] to [5], wherein the method for assessing fatigue in the subject is a non-medical method.

[0016] [7] Use of a lactate measurement kit or lactate meter capable of measuring the lactate concentration in tears in a method for assessing fatigue in a subject.

[0017] [8] The use according to [7], wherein the method for assessing fatigue in the subject is a method according to any one of [1] to [6].

[0018] [9] A lactate measurement kit or lactate meter capable of measuring the lactate concentration in tears, for use in a method for assessing fatigue in a subject.

[0019]

[10] The lactate measuring kit or lactate measuring device according to [9], wherein the method for evaluating fatigue in the subject is a method according to any one of [1] to [6].

[0020]

[11] Use of the concentration of lactic acid in tears collected from a subject as an index for assessing fatigue in the subject.

[0021]

[12] The use according to

[11] as an index for assessing fatigue in a subject in the method according to any one of [1] to [6].

[0022]

[13] A lachrymatory component generating kit for use in a method for assessing fatigue in a subject, comprising LFS (lacrimatory component generating enzyme), alliinase, and PRENCSO (S-1-propenylcysteine ​​sulfoxide).

[0023]

[14] Use of a lachrymatory component generating kit containing LFS (lacrimatory component generating enzyme), alliinase, and PRENCSO (S-1-propenylcysteine ​​sulfoxide) in a method for assessing fatigue in a subject.

[0024]

[15] The use according to

[14] , wherein the method for assessing fatigue in the subject is a method according to any one of [1] to [6].

[0025]

[16] Use of LFS (lacrimatory component generating enzyme), alliinase, and PRENCSO (S-1-propenylcysteine ​​sulfoxide) in the manufacture of a lachrymatory component generating kit for use in a method for assessing fatigue in a subject.

[0026]

[17] The use according to

[16] , wherein the method for assessing fatigue in a subject is a method according to any one of [1] to [6].

[0027]

[18] A system for evaluating fatigue of a subject, comprising: a memory unit, an input unit, a data processing unit, and an output unit; the memory unit stores a reference value of the concentration of lactic acid in tears and information on the degree of fatigue corresponding to the reference value, input from the input unit; the memory unit further stores a measured value of the concentration of lactic acid in tears of the subject input from the input unit; the data processing unit compares the measured value of the concentration of lactic acid in tears of the subject, stored in the memory unit, with the reference value, to determine information on the degree of fatigue of the subject; and the data processing unit further outputs the determined information on the degree of fatigue of the subject to the output unit.

[0028]

[19] The system described in

[18] , further comprising a measurement unit, which measures the concentration of lactic acid in the tear fluid of the subject to determine a measurement value, and outputs the determined measurement value to the input unit.

[0029]

[20] The system according to

[18] or

[19] , further comprising the lachrymatory component generating kit according to

[13] , wherein the tear fluid of the subject is collected by contacting the lachrymatory component generated by mixing the LFS, the alliinase, and the PRENCS0 in the lachrymatory component generating kit with the subject's eyes to stimulate the secretion of the tear fluid, and collecting the secreted tear fluid.

[0030] This specification includes the disclosure of Japanese Patent Application No. 2024-102782, from which the present application claims priority. All publications, patents, and patent applications cited in this specification are incorporated herein by reference in their entirety.

[0031] The method for assessing fatigue and the kit and system for assessing fatigue according to the present invention enable non-invasive assessment of fatigue in a subject, and are therefore useful for assessing fatigue for purposes such as designing training intensity and evaluating training effects.

[0032] FIG. 1 shows the results of measuring lactate concentrations in tears of two subjects before and after running exercise in Experiment 1. FIG. 2 shows the results of measuring lactate concentrations in tears and blood of two subjects before and after running exercise in Experiment 2. FIG. 3 shows the results of measuring lactate concentrations in tears of four subjects in the morning, afternoon, and evening over five days in Experiment 3. FIG. 4 shows the results of measuring lactate concentrations in tears while gradually increasing the running exercise load in Experiment 4. FIG. 5 is a graph showing the correlation between lactate concentrations in tears and lactate concentrations in blood measured at multiple time points before and after running exercise in Experiment 5. FIG. 6 is a configuration diagram of a system for assessing fatigue in a subject according to the present disclosure.

[0033] 1. Subject In the present disclosure, the term "subject" refers to a subject whose fatigue is being evaluated. The subject is typically a mammal, such as a human or a non-human mammal such as a horse.

[0034] 2. Method for assessing fatigue The present disclosure first relates to a method for assessing fatigue in a subject, the method comprising a measuring step of measuring a concentration of lactic acid in tears collected from the subject, wherein the concentration of lactic acid in the tears is an index for assessing fatigue in the subject.

[0035] The method according to the present disclosure was developed based on the unexpected finding that the concentration of lactic acid in tears collected from a subject serves as an index for assessing fatigue in the subject, specifically, that the higher the concentration of lactic acid in tears, the greater the subject's level of fatigue. While the concentration of lactic acid in blood has traditionally been known as an index of fatigue, as described in Non-Patent Document 2 (International Ophthalmology Clinics 40(4): pp. 113-122, Fall 2000), the component composition of blood and the component composition of tears do not necessarily correlate. Therefore, it was unexpected for those skilled in the art that the concentration of lactic acid in tears can serve as an index for assessing fatigue in a subject. In this specification, lactic acid refers to L-lactic acid unless otherwise specified.

[0036] Because tears can be collected non-invasively without the risk of infection, the method for assessing fatigue according to the present disclosure has the advantage that it can be used in a variety of situations. For example, the method for assessing fatigue according to the present disclosure can be used to assess fatigue in a subject during or after physical exercise, and the results of the fatigue assessment obtained can be used for purposes such as designing training intensity, evaluating the training effect, and evaluating the cool-down period after training.

[0037] In the measuring step, the concentration of lactic acid in tears collected from the test subject is measured. The method for measuring the concentration of lactic acid in tears is not particularly limited. For example, the concentration of lactic acid in tears can be measured using a commercially available lactate measurement kit. The lactate measurement kit can include, for example, L-lactate dehydrogenase (LDH) and a reducing color reagent. LDH contains NAD(H) as a coenzyme. In the presence of LDH, lactate is oxidized to pyruvic acid, and as a result, NAD ＋ is reduced to NADH. Lactic acid can be quantified by quantifying the generated NADH using a reducing colorimetric reagent. Examples of reducing colorimetric reagents include tetrazolium salts such as WST-1. The lactate measurement kit can further include a buffer used in lactate measurement, a microwell plate, and an L-lactate standard sample of known concentration. Alternatively, the lactate concentration in tears can be measured by analyzing tears instead of blood as a sample using a commercially available measuring device for measuring the lactate concentration in blood. Examples of lactate measuring devices that can be used include a lactate measuring device equipped with a sensor containing an enzyme membrane on which L-lactate oxidase (LOD) is immobilized. The sensor can further include an electrode that electrochemically detects the decrease in oxygen or the increase in hydrogen peroxide in the reaction in which LOD converts lactate and oxygen to produce pyruvic acid and hydrogen peroxide. Alternatively, the concentration of lactate in tears can be measured by analyzing tears or a processed product thereof as a sample using an analytical device such as a liquid chromatograph, gas chromatograph, or mass spectrometer.

[0038] The method for assessing fatigue according to the present disclosure may further include an evaluation step of evaluating the fatigue of the subject based on the concentration of lactic acid in the tear fluid. In the evaluation step, for example, reference values ​​for the tear lactate concentration obtained by measuring the lactate concentration in tears collected from the subject at multiple time points with different degrees of fatigue and information on the subject's degree of fatigue corresponding to the reference values ​​are prepared in advance, and the measured tear lactate concentration obtained in the measurement step is compared with the reference values ​​to evaluate the subject's degree of fatigue. Here, the tear fluid used to prepare the reference values ​​and information may be collected from the same individual as the subject to be evaluated, or may be collected from one or more individuals of the same species as the subject to be evaluated. The reference value may be a specific numerical value or a numerical range with a specified upper and / or lower limit. The reference value may also be a single numerical value or a numerical range, or multiple numerical values ​​or numerical ranges. For example, if it is known that physical exercise to a predetermined level of fatigue is highly effective in training, the lactate concentration in the tear fluid of the subject at the time when fatigue reaches the predetermined level can be set as a threshold value. If the lactate concentration in the tear fluid measured in the measurement step is below the threshold or in a range below the threshold (this numerical range may be referred to as a "first reference value"), fatigue can be evaluated as "not fatigued" or "insufficient training effect." If the lactate concentration in the tear fluid is above the threshold or in a range above the threshold (this numerical range may be referred to as a "second reference value"), fatigue can be evaluated as "fatigue present" or "sufficient training effect." Examples of the threshold value include the lactate concentration in the tear fluid measured at the lactate threshold (LT), at which the blood lactate concentration begins to increase rapidly with increasing exercise intensity, or at the lactate accumulation onset (OBLA), at which lactate accumulation begins. An example of a lactate concentration in the tear fluid measured at the blood lactate concentration OBLA, which can serve as the threshold, is 4 mmol / L. In the evaluation step, the reference value may be set to two or more or three or more stages, and the degree of fatigue may be classified and evaluated in accordance with the set of stages.

[0039] The method for assessing fatigue according to the present disclosure may further include a collection step of collecting tears from a test subject. The collection step preferably includes contacting the test subject's eyes with a tear-producing component generated by mixing LFS (lacrimatory component-generating enzyme), alliinase, and PRENCESO to stimulate tear secretion, and collecting the secreted tears. Specific aspects of LFS, alliinase, and PRENCESO will be described in relation to the lacrimal component-generating kit. The collection step enables tears to be collected from the test subject non-invasively and easily.

[0040] Each step of the method for assessing fatigue according to the present disclosure may be performed by an individual who is not a physician, or may be performed by a professional such as a medical assistant, a sports instructor, a veterinarian, etc. Thus, the method for assessing fatigue according to the present disclosure may be a non-medical method even when the subject is a human, and may be, for example, a preliminary method for assessing fatigue or a method for assisting in assessing fatigue.

[0041] <3. Lacrimal component generating kit for use in method for assessing fatigue> Secondly, the present disclosure relates to a lacrimal component generating kit for use in a method for assessing fatigue in a subject, the kit comprising LFS (a lacrimal component-generating enzyme), alliinase, and PRENCEO (S-1-propenylcysteine ​​sulfoxide).

[0042] By mixing the LFS, alliinase, and PRENCESO that constitute the lachrymatory component generating kit of the present disclosure, alliinase acts on PRENCESO to generate E-1-propenesulfenic acid, which is then isomerized by LFS to generate the lachrymatory component (thiopropanal S-oxide). Contacting the generated lachrymatory component with the subject's eyes promotes tear secretion, and the secreted tear can be collected and used as a sample in the method for assessing fatigue of the present disclosure. Using the lachrymatory component generating kit of the present disclosure, tears can be collected from the subject noninvasively and easily. Mixing of LFS, alliinase, and PRENCESO can be performed in an appropriate solvent, such as water or an aqueous buffer solution.

[0043] LFS that can be used includes those derived from Alliaceae plants such as onion and produced by genetic engineering, as well as mutant enzymes thereof, such as those described in International Publication WO 02 / 020808 and International Publication WO 03 / 074707. Onion-derived LFS prepared by the genetic engineering method described in International Publication WO 02 / 020808 is preferred. LFS isolated from Alliaceae plants can also be used. The LFS isolated from Alliaceae plants may be purified or crudely purified. Crudely purified LFS is obtained, for example, by extraction from onion by a simple method. A simple method for preparing crudely purified LFS includes treating an extract of pulverized onion with water with an anion exchange resin, allowing the resin to adsorb, and then eluting the LFS.

[0044] The alliinase may be derived from a plant of the Alliaceae family, and preferably derived from garlic.As the alliinase, it is preferable to use alliinase isolated from a plant of the Alliaceae family.The alliinase isolated from a plant of the Alliaceae family may be purified or crudely purified.The crude alliinase is, for example, extracted from garlic by a simple method.A simple method for preparing crude alliinase includes adding acid to an extract of garlic that has been hydrated and crushed, causing isoelectric precipitation of alliinase, and then collecting and redissolving the precipitate.

[0045] The lachrymatory component generating kit according to the present disclosure may comprise LFS, alliinase, and PRENCS0 as three separate components, or may comprise a composition containing the enzymes LFS and alliinase and the substrate PRENCS0 as two separate components.

[0046] In a preferred embodiment, the lachrymatory component generating kit according to the present disclosure comprises: (1) an enzyme composition prepared by drying a solution containing LFS (a lachrymatory component generating enzyme) and alliinase; and (2) PRENCS0.

[0047] According to the enzyme composition (1), the unstable LFS is stably maintained together with alliinase. When preparing the enzyme composition (1), it is preferable to further add a protecting agent to the solution and then dry it. Examples of the protecting agent include sugars, and the sugars are preferably disaccharides. Examples of disaccharides include one or more disaccharides selected from sucrose, trehalose, maltose, lactose, and cellobiose. The protecting agent may contain a salt in addition to the sugar. Examples of the salt include any salt, such as KCl, MgCl, etc. ２ , NaCl, etc., with NaCl being particularly preferred. Furthermore, the protecting agent may also contain pyridoxal phosphate. As a drying method for preparing the enzyme composition of (1) above, freeze-drying or hot air drying is preferred. In the case of hot air drying, it is preferable to dry within a temperature range in which the enzyme is not inactivated by heat, for example, 40°C to 80°C, preferably 55°C to 65°C.

[0048] The PRENCS0 in (2) may be provided as a powder or an aqueous solution. The aqueous solution of PRENCS0 is preferably adjusted to an acidic pH for stability.

[0049] More preferred embodiments of the enzyme composition (1) and the PRENCS0 (2) are as described in Patent Document 1 (JP 2008-285476 A).

[0050] 4. System for Assessing Fatigue Thirdly, the present disclosure relates to a system for assessing fatigue configured to implement the method for assessing fatigue according to the present disclosure. Fig. 6 is a configuration diagram of the system for assessing fatigue according to the present disclosure. The system for assessing fatigue 1 according to the present disclosure shown in Fig. 6 includes a memory unit 11, an input unit 12, a data processing unit 13, and an output unit 14, and preferably further includes a measurement unit 15. Of the system 1, the memory unit 11, the input unit 12, the data processing unit 13, and the output unit 14 can be realized by, for example, a computer system including one or more central processing units (CPUs) and one or more storage devices.

[0051] Each component of the system 1 for assessing fatigue according to the present disclosure has the following functions.

[0052] The storage unit 11 stores information on the reference value of the concentration of lactic acid in tears and the degree of fatigue corresponding to the reference value, which are input from the input unit 12. Specific examples of the reference value and the information on the degree of fatigue corresponding to the reference value are as described in relation to the evaluation step of the method for evaluating fatigue according to the present disclosure.

[0053] The memory unit 11 further stores the measured value of the concentration of lactic acid in the tear fluid of the subject input from the input unit 12. The input measured value may be a value measured in advance, or may be a value measured by the measurement unit 15 as described below.

[0054] The data processing unit 13 compares the measured value of the lactic acid concentration in the tear fluid of the subject stored in the memory unit 11 with the reference value, and determines information on the degree of fatigue of the subject.

[0055] The data processing unit 13 further outputs information on the determined degree of fatigue of the subject to the output unit 14 .

[0056] The measurement unit 15 measures the concentration of lactic acid in the tear fluid of the subject to determine a measurement value, and outputs the determined measurement value to the input unit 12.

[0057] The storage unit 11 may be in the form of a memory device such as a RAM, a ROM, or a flash memory, a fixed disk device such as a hard disk drive, or a portable storage device such as an optical disk. The storage unit 11 stores data such as data and instructions input from the input unit 12 and results of arithmetic processing by the data processing unit 13, and can further store computer programs executed by the data processing unit 13, databases, etc., as necessary.

[0058] The input unit 12 is an interface and includes an operation unit such as a touch panel, keyboard, mouse, etc. This allows the input unit 12 to input data measured by the measurement unit 15, instructions for arithmetic processing to be performed by the data processing unit 13, etc. Furthermore, the input unit 12 may include, for example, an interface unit separate from the operation unit that allows input of data such as reference values ​​for the concentration of lactic acid in tears and information on the degree of fatigue corresponding to the reference values, and data such as measurement values ​​measured by the measurement unit 15 via a network or a storage medium.

[0059] The data processing unit 13 includes a central processing unit (CPU). The data processing unit 13 performs various arithmetic operations in accordance with the program stored in the memory unit 11 to determine information on the subject's degree of fatigue by comparing the measured value of the lactic acid concentration in the tear fluid of the subject with a reference value of the lactic acid concentration in the tear fluid, both of which are stored in the memory unit 11. The data processing unit 13 includes the memory unit 11, the input unit 12, and the output unit 14, and, if necessary, a functional module for controlling the measurement unit 15, and is capable of performing various controls.

[0060] The output unit 14 is configured to output information on the degree of fatigue of the subject determined in the data processing unit 13. The information determined in the data processing unit 13 may be output directly to the output unit 14, or may be temporarily stored in the storage unit 11 and then output to the output unit 14 as needed. The output unit 14 may be a display device such as a display or a printing device such as a printer that displays the results of the arithmetic processing, or may be an interface unit for outputting to an external storage device directly or via a network.

[0061] The measurement unit 15 measures the concentration of lactic acid in the tear fluid of the subject to determine a measurement value and outputs the determined measurement value to the input unit 12. Therefore, the measurement unit 15 has a configuration that enables measurement of the concentration of lactic acid in the tear fluid. Specific examples of the measurement unit 15 include analytical instruments such as a liquid chromatograph, a gas chromatograph, and a mass spectrometer, as well as a lactate meter capable of measuring the lactic acid concentration in the tear fluid. Data measured by the measurement unit 15 can be output from the input unit 12 to the memory unit 11 via a network or a storage medium. The measurement unit 15 is not a required component; for example, the user of the system 1 can input a measurement value obtained by measuring the lactic acid concentration in the tear fluid of the subject using the means described in the measurement step of the method for assessing fatigue according to the present disclosure into the input unit 12.

[0062] The system 1 according to the present disclosure may further include a lachrymatory component generating kit 16 according to the present disclosure. The configuration of the lachrymatory component generating kit 16 is as described above, and therefore description thereof will be omitted.

[0063] According to the system 1 of the present disclosure, which further includes a lachrymatory component generating kit 16, tears can be collected from a subject by: contacting the eye of the subject with a lachrymatory component generated by mixing LFS, alliinase, and PRENCS0 contained in the lachrymatory component generating kit 16 to stimulate the secretion of tears; and collecting the secreted tears. A measured value of the lactic acid concentration in the subject's tears collected using the lachrymatory component generating kit 16 is stored in the memory unit 11 via the input unit 12, and the subject's level of fatigue is evaluated based on the measured value. In an embodiment in which the system 1 includes a measuring unit 15, the lactic acid concentration in the collected tears can be measured by the measuring unit 15. In an embodiment in which the system 1 does not include a measuring unit 15, the lactic acid concentration in the collected tears can be measured separately by external means, and the obtained measured value can be input into the input unit 12 of the system 1.

[0064] Experiment 1: Two subjects (subjects a and b) ran for 5 minutes on a treadmill at a speed of 13 km / h (subject a) or 15 km / h (subject b). Tear fluid was collected from each subject before and after the running exercise.

[0065] The lactate concentration in tears collected from two subjects before and after running exercise was measured using a commercially available lactate assay kit, Lactate Assay Kit-WST (Dojin Chemical Research Institute).

[0066] The measurement results are shown in Figure 1. In both subjects, the lactate concentration in tears increased due to the stress of running exercise.

[0067] The tear fluid was collected from the subjects by generating a tear stimulating substance using the tear stimulating substance generating kit described in Patent Document 1 (JP 2008-285476 A), contacting the tear stimulating substance with the subject's eyes, and collecting the resulting tear fluid.

[0068] The lachrymatory component generating kit includes an enzyme composition prepared by freeze-drying a solution containing onion-derived LFS (lacrimatory component generating enzyme) and garlic-derived alliinase, and a PRENCOS solution prepared by dissolving PRENCSO in phosphate buffer (pH 6.5), and the lachrymatory component (LF) is generated by mixing the two.

[0069] Experiment 2: Two subjects (subjects c and d) ran on a treadmill for 5 minutes at a speed of 13 km / h (subject c) or 15 km / h (subject d). The lactate concentrations in each subject's tear and blood were measured before and after the running exercise. The tear collection method was as described in Experiment 1. The lactate concentration in the collected tear was measured using a simple blood lactate meter, Lactate Pro2 (Arkray).

[0070] The blood lactate concentration was measured using the simple blood lactate measuring device.

[0071] The measurement results are shown in Figure 2. It was confirmed that the stress of running exercise increases the lactate concentrations in both blood and tears.

[0072] Experiment 3 Tear fluid was collected from four subjects (Subjects A, B, C, and D) in the morning, afternoon, and evening over a period of five days, and the concentration of lactic acid in the tear fluid was measured.

[0073] The tear fluid was collected in the same manner as in Experiments 1 and 2. The lactic acid concentration in the collected tear fluid was measured using a commercially available lactate assay kit, Lactate Assay Kit-WST (Dojin Chemical Research Institute).

[0074] FIG. 3 shows the measurement results of lactate concentrations in tears collected from four subjects in the morning, afternoon, and evening over five days.

[0075] It has been shown that the concentration of lactate in tears collected from the same subject can vary within and between days.

[0076] Experiment 4 Two subjects (subjects P and Q) underwent a progressive load test using a treadmill under the following conditions.

[0077] First, as a warm-up (W-up), the subjects ran at a constant speed of 7 km / h for 3 minutes, followed by a 1-minute rest.

[0078] Next, participants completed eight cycles of running exercise, consisting of three minutes at a constant speed followed by one minute of rest. The running speed was 7 km / h in the first cycle and increased by 1 km / h each time until reaching 14 km / h in the eighth cycle.

[0079] After the warm-up and during rest after each cycle of running exercise, tears were collected from the subjects, and the lactate concentration in the tears was measured.

[0080] The tear collection and measurement of lactic acid concentration were carried out in the same manner as in Experiment 2.

[0081] The measurement results of the lactic acid concentration in the tears collected from two subjects P and Q at each time point are shown in FIG.

[0082] It was confirmed that the concentration of lactic acid in tears increases as the load of running increases. This result indicates that the concentration of lactic acid in tears can be used as an indicator of fatigue caused by physical exercise.

[0083] Experiment 5: Two subjects (subject X, Y) ran on a treadmill for three minutes at a speed of 14 km / h (subject X) or 10 km / h (subject Y). Lactic acid concentrations in the tear fluid and blood of each subject were measured before the running exercise, immediately after the end of the exercise, and several minutes after the end of the exercise (subject X at one time point and subject Y at two times point).

[0084] The lactate concentrations in the tear fluid and blood were measured in the same manner as in Experiment 2.

[0085] The measurement results of lactate concentrations in tears and blood at each time point are shown in the table below.

[0086]

[0087]

[0088] Figure 5 shows a graph plotting the lactate concentration in tears on the horizontal axis and the lactate concentration in blood on the vertical axis. It is known that the lactate concentration in blood correlates with fatigue level and serves as an index of fatigue level. The results in Figure 5 confirm that the lactate concentration in tears shows a positive correlation with the lactate concentration in blood, and is useful as an index of fatigue level.

Claims

1. A method for assessing fatigue in a subject, comprising a measuring step of measuring the concentration of lactic acid in tears collected from the subject, wherein the concentration of lactic acid in the tears is an index for assessing fatigue in the subject.

2. The method of claim 1, further comprising an evaluation step of evaluating fatigue in the subject based on the concentration of lactic acid in the tear fluid.

3. The method according to claim 1 or 2, wherein the tear fluid is collected from the subject during or after physical exercise.

4. The method according to any one of claims 1 to 3, further comprising a collection step of collecting the tears from the test subject, the collection step comprising: contacting the eye of the test subject with a lacrimatory component generated by mixing LFS (lacrimatory component generating enzyme), alliinase, and PRENCESO (S-1-propenylcysteine ​​sulfoxide) to stimulate the secretion of the tears; and collecting the secreted tears.

5. A lachrymatory component generating kit for use in a method for assessing fatigue in a subject, comprising LFS (lacrimatory component generating enzyme), alliinase, and PRENCEO (S-1-propenylcysteine ​​sulfoxide).

6. A system for assessing fatigue in a subject, comprising a memory unit, an input unit, a data processing unit, and an output unit, wherein the memory unit stores information on a reference value of the concentration of lactic acid in tears and a degree of fatigue corresponding to the reference value, input from the input unit, the memory unit further stores a measured value of the concentration of lactic acid in tears of the subject input from the input unit, the data processing unit compares the measured value of the concentration of lactic acid in tears of the subject stored in the memory unit with the reference value to determine information on the degree of fatigue of the subject, and the data processing unit further outputs the determined information on the degree of fatigue of the subject to the output unit.

7. The system according to claim 6, further comprising a measurement unit that measures the concentration of lactic acid in the tear fluid of the subject to determine a measurement value, and outputs the determined measurement value to the input unit.

8. The system according to claim 6 or 7, further comprising the lachrymatory component generating kit according to claim 5, wherein the tear fluid of the subject is collected by: contacting the lachrymatory component generated by mixing the LFS, the alliinase, and the PRENCS0 in the lachrymatory component generating kit with the subject's eyes to stimulate the secretion of the tear fluid; and collecting the secreted tear fluid.

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