Method and system for determining exercise intensity at onset of lactic acid accumulation

Abstract

The present invention provides an exercise intensity determination system for identifying, using a non-invasive method, the onset of lactic acid accumulation.　An exercise intensity determination system (100) comprises a control device (20). The control device (20) determines an HR value, which is the heart rate of an exerciser (A), calculates an LF value, which is the integral of a low-frequency component obtained from a heart rate variability frequency of the exerciser (A), generates an evaluation curve plotted by setting exercise intensity on the horizontal axis and HR / LF on the vertical axis, calculates the slope of the change in HR / LF in each of prescribed exercise intensity sections on the evaluation curve, and identifies an exercise intensity at which the slope exhibits a maximum value as the exercise intensity at the onset of lactic acid accumulation.

Description

Method and system for determining exercise intensity at lactic acid accumulation start point

[0001] The present invention relates to a method for determining the exercise intensity (optimum exercise intensity) at the lactic acid accumulation start point of an exerciser performing training using an exercise apparatus with variable load, a program for causing a computer to execute the method, an exercise intensity determination system for determining the exercise intensity at the lactic acid accumulation start point of the exerciser, and an exercise apparatus incorporating the exercise intensity determination system.

[0002] The present inventor has previously proposed, as one of the methods for evaluating whether an exerciser performing training using an exercise apparatus is able to perform training effectively, an evaluation method using the heart rate (HR value) of the exerciser and the integrated value of the low-frequency component (LF value) obtained by performing power spectrum analysis on the heart rate variability frequency.

[0003] Specifically, it has been found that HR / LF, which is a value obtained by dividing the HR value (the exerciser's heart rate) by the LF value (the integrated value of the low-frequency component obtained by performing power spectrum analysis on the heart rate variability frequency), can be used for the above evaluation (Patent Document 1).

[0004] Furthermore, the present inventors have also proposed a method for obtaining the optimum exercise intensity as training aimed at functional improvement, using the integrated value of the high-frequency component (HF value) obtained by performing power spectrum analysis on the heart rate variability frequency (Non-Patent Documents 1 and 2).

[0005] This method is a method for specifying the optimum exercise intensity from a first transition graph of the HR / LF ratio in which the horizontal axis represents exercise intensity and the vertical axis represents the logarithmic value of the HR / LF ratio, and a second transition graph of the HF value in which the horizontal axis represents exercise intensity and the vertical axis represents the logarithmic value of the HF value.

[0006] Specifically, when the first transition graph that is a straight line rising to the right and the second transition graph that is a straight line falling to the right are drawn on the same graph, the exercise intensity at one point where these two transition graphs intersect is defined as the optimum exercise intensity.

[0007] It has been confirmed that the exercise intensity determined in this way is close to 100% of the lactic acid work threshold (LT) determined from the actually measured blood lactic acid level, and can be regarded as the optimum exercise intensity.

[0008] Patent No. 7493811

[0009] Yoshinari Uehara, Special Feature: Concepts and Setting Methods for "Exercise Intensity"—Development of a New Index for Safely and Easily Measuring Exercise Intensity, Coaching Clinic 2020; 34(11): 14-17. Yukiya Tagami; Yoshinari Uehara, An Attempt at a New Exercise Intensity Assessment Method Utilizing Autonomic Nervous System Components in Heart Rate Variability, Bio Industry 2021; 38(3): 82-86.

[0010] Subsequent research revealed that HF ​​values ​​are affected by exercise type and respiratory rate. Therefore, there was a risk that evaluation using HF values, and consequently HR / LF values, did not accurately assess exercise intensity.

[0011] Furthermore, it has become globally known that the optimal exercise intensity for athletes is when their blood lactate concentration reaches 4 mmol / L, and there is a growing demand to determine exercise intensity by focusing on lactate. The exercise intensity at which the blood lactate concentration reaches 4 mmol / L after the start of exercise is known as the so-called lactate accumulation initiation point.

[0012] The inventors conducted further research and discovered a method for identifying the exercise intensity at which lactate accumulation begins, leading to the present invention.

[0013] The present invention provides a method for determining the exercise intensity at the lactate accumulation initiation point, which comprises: a step (S4) of increasing the exercise intensity of the exercise equipment (10); a step (S5) of identifying the value of HR, which is the heart rate of the exerciser at a predetermined exercise intensity; a step (S6) of calculating the value of LF, which is the integral value of the low-frequency component obtained from the heart rate variability frequency of the exerciser at the predetermined exercise intensity; a step (S7) of generating an evaluation curve with the exercise intensity on the horizontal axis and HR / LF on the vertical axis; and a step (S9) of calculating the slope of the amount of change in HR / LF for each predetermined exercise intensity interval in the evaluation curve, and identifying the exercise intensity at which the slope shows the maximum value as the exercise intensity at the lactate accumulation initiation point (S).

[0014] Furthermore, the method for determining the exercise intensity at the lactate accumulation initiation point of the present invention is characterized by repeatedly applying regression analysis to the evaluation curve for each predetermined exercise intensity interval multiple times, and identifying the exercise intensity at the lactate accumulation initiation point as the exercise intensity at which the value obtained from the final regression analysis is maximized.

[0015] Furthermore, the method for determining the exercise intensity at the point where lactic acid accumulation begins according to the present invention is characterized in that the horizontal axis of the evaluation curve is the value obtained by logarithmically transforming the exercise intensity, instead of the exercise intensity itself.

[0016] Furthermore, the method for determining the exercise intensity at the lactate accumulation initiation point of the present invention is characterized in that the vertical axis of the evaluation curve is 1 / LF instead of HR / LF.

[0017] The program of the present invention is a program for causing a computer to execute the above method. The program of the present invention can be recorded on a computer-readable recording medium.

[0018] The exercise intensity determination system (100) of the present invention determines the exercise intensity at the lactate accumulation start point (S) of an exerciser (A) using an exercise device (10) with variable load from the heart rate information of the exerciser (A), and comprises: an exercise intensity control means (21A) for controlling the exercise intensity of the exercise device (10); an HR determination means (21B) for determining the value of HR, which is the heart rate of the exerciser at a predetermined exercise intensity; an LF calculation means (21C) for calculating the value of LF, which is the integral value of the low-frequency component obtained from the heart rate variability frequency of the exerciser at the predetermined exercise intensity; an evaluation curve generation means (21D) for generating an evaluation curve with the exercise intensity on the horizontal axis and HR / LF on the vertical axis; and an exercise intensity identification means (21F) for calculating the slope of the amount of change of HR / LF for each predetermined exercise intensity interval in the evaluation curve and identifying the exercise intensity at which the slope shows the maximum value as the exercise intensity at the lactate accumulation start point (S).

[0019] The exercise intensity determination system (100) of the present invention is characterized in that the exercise intensity identification means (21F) repeatedly applies regression analysis to the evaluation curve for each predetermined exercise intensity interval multiple times, and identifies the exercise intensity at which the value obtained from the final regression analysis is maximized as the exercise intensity at the lactate accumulation initiation point (S).

[0020] The exercise intensity determination system (100) of the present invention is characterized in that the horizontal axis of the evaluation curve is a value obtained by logarithmically transforming the exercise intensity, instead of the exercise intensity itself.

[0021] The exercise intensity determination system (100) of the present invention is characterized in that the vertical axis of the evaluation curve is 1 / LF instead of HR / LF.

[0022] The exercise equipment (10) of the present invention is an exercise equipment (10) that incorporates the above-mentioned exercise intensity determination system (100), wherein the exercise intensity control means (21A) maintains the exercise intensity of the exercise equipment (10) at the exercise intensity at the lactic acid accumulation initiation point (S) after the exercise intensity at the lactic acid accumulation initiation point (S) has been identified.

[0023] The reference numerals in parentheses are solely for the purpose of indicating the correspondence with the embodiments described later, and do not limit the scope of the rights.

[0024] In this invention, using an exercise device with variable load, the exerciser's heart rate (HR) and the integrated value (LF) of the low-frequency component obtained by power spectral analysis of the heart rate variability frequency are measured while increasing the load. An evaluation curve is generated with exercise intensity on the horizontal axis and HR / LF on the vertical axis. The slope of the change in HR / LF for each predetermined exercise intensity interval on this evaluation curve is calculated, and the exercise intensity at which the slope shows the maximum value is identified as the point at which lactic acid accumulation begins.

[0025] The point where the slope of the change in HR / LF reaches its maximum value and HR / LF does not decrease thereafter is identified as the point where lactate accumulation begins, and the exercise intensity at that point is determined as the exercise intensity at the start of lactate accumulation.

[0026] The exercise intensity at which lactate accumulation begins, as determined in this way, corresponds with high accuracy to the optimal exercise intensity determined based on blood lactate levels measured from blood tests of each exerciser.

[0027] Thus, according to the present invention, it is possible to accurately determine the exercise intensity at which lactic acid accumulation begins, i.e., the optimal exercise intensity, non-invasively without performing blood tests or other invasive examinations, and to suggest the optimal exercise intensity without placing a heavy burden on the exerciser.

[0028] In particular, by maintaining the exercise intensity at the point where lactic acid accumulation begins, it becomes possible to achieve the maximum training effect for each individual exerciser.

[0029] Figure 1 is a perspective view of an exercise intensity determination system and an exercise device controlled by the exercise intensity determination system according to a first embodiment of the present invention. Figure 2 is a block diagram showing the internal structure of the control device. Figure 3 is a block diagram showing the functions performed by the central processing unit. Figure 1 is a flowchart showing the operation of the exercise intensity determination system. Figure 1 is a graph of the evaluation curve for subject 1. Figure 5 is a line graph obtained by approximating the plot of the evaluation curve shown in Figure 5 with a straight line. Figure 2 is a graph of the evaluation curve for subject 2. Figure 7 is a line graph obtained by approximating the plot of the evaluation curve shown in Figure 7 with a straight line. Figure 3 is a graph of the evaluation curve for subject 3. Figure 9 is a line graph obtained by approximating the plot of the evaluation curve shown in Figure 9 with a straight line. Figure 7 is a graph of the evaluation curve for subject 2 when the 1 / LF value is used on the vertical axis instead of the HR / LF value. Figure 5 is a graph of the evaluation curve when the exercise intensity is logarithmically transformed as the horizontal axis of the evaluation curve graph shown in Figure 5. Figure 7 is a graph of the evaluation curve when the exercise intensity is logarithmically transformed as the horizontal axis of the evaluation curve graph shown in Figure 7. Figure 9 is a graph of the evaluation curve when the exercise intensity is logarithmically transformed as the horizontal axis of the evaluation curve graph shown in Figure 9. This is a graph of an evaluation curve showing a second method for determining the point at which lactic acid accumulation begins.

[0030] (First Embodiment) Figure 1 is a perspective view of an exercise intensity determination system 100 and an exercise device controlled by the exercise intensity determination system 100 according to the first embodiment of the present invention.

[0031] The exercise intensity determination system 100 is connected via a control signal cable 11 to a bicycle ergometer 10, which is an exercise device that can adjust the load to any value.

[0032] The exercise intensity determination system 100 is equipped with a control device 20. Figure 2 is a block diagram showing the internal structure of the control device 20.

[0033] As shown in Figure 2, the control device 20 consists of a central processing unit (CPU) 21, a first memory 22 consisting of ROM, a second memory 23 consisting of RAM, an input interface 24 for transferring various commands and data input to the control device 20 to the central processing unit 21, an output interface 25 for outputting calculation results executed by the central processing unit 21 to the outside, and a bus 26 connecting the central processing unit 21 to the first memory 22, the second memory 23, the input interface 24, and the output interface 25, respectively.

[0034] The first memory 22 stores various control programs executed by the central processing unit 21 and other data that cannot be rewritten.

[0035] The second memory 23 stores various data and parameters, and also provides an operating area for the central processing unit 21; that is, it stores data that is temporarily required for the central processing unit 21 to execute various control programs.

[0036] The central processing unit 21 reads a program from the first memory 22 and executes it. In other words, the central processing unit 21 operates according to the program stored in the first memory 22. In this embodiment, the first memory 22 stores a program that determines the exercise intensity at which lactic acid accumulation begins for exerciser A, who is training using the bicycle ergometer 10. The central processing unit 21 operates according to this program and determines the exercise intensity at which lactic acid accumulation begins for exerciser A. In other words, the control device 20 functions as an exercise intensity determination system 100.

[0037] Figure 3 is a block diagram showing the functions performed by the central processing unit 21.

[0038] As shown in Figure 3, the central processing unit 21 functions as: exercise intensity control means 21A for controlling the load (exercise intensity) of the bicycle ergometer 10; HR determination means 21B for determining the value of HR, which is the heart rate of exerciser A at a predetermined exercise intensity; LF calculation means 21C for calculating the value of LF, which is the integral value of the low-frequency component obtained from the heart rate variability frequency of exerciser A at a predetermined exercise intensity; evaluation curve generation means 21D for generating an evaluation curve with exercise intensity on the horizontal axis and HR / LF on the vertical axis; rise start point identification means 21E for identifying the starting point of the first rise in the evaluation curve generated by the evaluation curve generation means 21D; and exercise intensity identification means 21F for calculating the slope of the amount of change in HR / LF for each predetermined exercise intensity interval in the evaluation curve and identifying the exercise intensity at which the slope shows the maximum value as the exercise intensity at which lactic acid accumulation begins, i.e., the optimal exercise intensity.

[0039] Electrodes 31 are attached to a total of four locations on the chest and abdomen of exerciser A, and each electrode 31 is connected to a heart rate monitor 30. The heart rate monitor 30 is connected to the input interface 24 of the control device 20 via a connecting cable 32.

[0040] The heart rate monitor 30 continuously measures the heart rate of exerciser A based on the electrical signals transmitted from the electrodes 31 and creates an electrocardiogram showing the heart rate over time. The created electrocardiogram data, along with exerciser A's heart rate, is sent from the heart rate monitor 30 to the input interface 24 of the control device 20 via the connecting cable 32 as exerciser A's heart rate information 33, and further sent to the central processing unit 21.

[0041] The exercise intensity control means 21A of the control device 20 transmits a control signal 34 to the bicycle ergometer 10 via the output interface 25 to increase or decrease the load (exercise intensity) of the bicycle ergometer 10.

[0042] Upon receiving heart rate information 33 of exerciser A from the heart rate monitor 30 via the input interface 24, the central processing unit 21 of the control device 20 operates as an HR determination means 21B and calculates the HR value, which is the heart rate value for each exercise intensity, from the electrocardiogram data of exerciser A.

[0043] The central processing unit 21 further operates as an LF calculation unit 21C, and calculates an LF value that is an integrated value of a low frequency component obtained by performing power spectrum analysis on the heartbeat fluctuation frequency of the heart rate (HR value).

[0044] Further, the central processing unit 21 also operates as an evaluation curve generation unit 21D that generates an evaluation curve with exercise intensity on the horizontal axis and the HR / LF value for each exercise intensity on the vertical axis, and operates as a rise start point identification unit 21E that identifies the start point (the point where the change amount of the slope first increases) of the first rise (the increase of the HR / LF value accompanying the increase in exercise intensity) on the generated evaluation curve. The rise start point identification unit 21E calculates the slope of the change amount of HR / LF for each predetermined exercise intensity section on the evaluation curve generated by the evaluation curve generation unit 21D, and identifies the exercise intensity at which the change amount of the slope first increases as the start point of the first rise.

[0045] Further, the central processing unit 21 operates as an exercise intensity identification unit 21F, calculates the slope of the change amount of HR / LF for each predetermined exercise intensity section on the evaluation curve, and identifies the exercise intensity at which the slope shows the maximum value as the exercise intensity (optimum exercise intensity) at the lactic acid accumulation start point where HR / LF rises sharply and does not fall thereafter.

[0046] FIG. 4 is a flowchart showing the operation of the exercise intensity determination system 100. Hereinafter, the operation of the exercise intensity determination system 100 will be described with reference to FIGS. 1 to 4. First, the exerciser A turns on the power buttons of the bicycle ergometer 10, the control device 20, and the heart rate monitor 30 (step S1).

[0047] Next, the exerciser A attaches the electrodes 31 of the heart rate monitor 30 at predetermined positions, and confirms that the heart rate can be measured (step S2).

[0048] When the heart rate monitor 30 cannot correctly detect the heart rate because the attachment position of the electrodes 31 is not appropriate, the correct attachment positions of the electrodes 31 are indicated to the exerciser A via the monitor 12 of the bicycle ergometer 10, and the exerciser A is made to reattach the electrodes 31.

[0049] After confirming that heart rate measurement is possible, the control device 20 displays a mode selection screen on the display screen 27 of the control device 20 or on the monitor 12 of the bicycle ergometer 10 (step S3).

[0050] On the mode selection screen, you can choose between a measurement mode that only measures the point at which lactate accumulation begins, and a training mode that, after identifying the point at which lactate accumulation begins, performs exercise for a predetermined time while maintaining the exercise intensity (optimal exercise intensity) at that point. The following assumes that the training mode is selected.

[0051] After the training mode is selected, the central processing unit 21 of the control device 20 operates as an exercise intensity control means 21A and sets the load of the bicycle ergometer 10 to the lowest exercise intensity. As a result, exerciser A starts exercising at the lowest exercise intensity (step S4).

[0052] Furthermore, if participant A is an athlete or other person with high athletic ability, it is also possible to allow participant A to set the initial load (exercise intensity) to any value that suits them.

[0053] After exerciser A begins, the central processing unit 21 functions as an HR determination means 21B and identifies the HR value, which is the heart rate of exerciser A, from the heart rate information and electrocardiogram information detected by the heart rate monitor 30 (step S5).

[0054] Next, the central processing unit 21 functions as an LF calculation means 21C and calculates the LF value, which is the integral value of the low-frequency components obtained by power spectral analysis of the heart rate variability frequency of exerciser A (step S6).

[0055] After calculating the HR value and LF value, the central processing unit 21 operates as an evaluation curve generation means 21D and generates an evaluation curve graph with exercise intensity on the horizontal axis and HR / LF on the vertical axis (step S7).

[0056] Next, the central processing unit 21 operates as an upward start point identification means 21E, monitoring the rise in the generated evaluation curve graph (the increase in HR / LF value accompanying the increase in exercise intensity), and identifies the first rising start point as the first rising point to appear (step S8).

[0057] Subsequently, the central processing unit 21 operates as an exercise intensity identification means 21F, calculates the slope of the change in HR / LF for each predetermined exercise intensity interval in the evaluation curve, and identifies the exercise intensity at which this slope shows the maximum value as the exercise intensity at the lactate accumulation initiation point (optimal exercise intensity) (step S9).

[0058] The optimal exercise intensity determined in this way is displayed, for example, on the monitor 12 of the bicycle ergometer 10, so that exerciser A can also see it.

[0059] The method for determining the exercise intensity at which lactic acid accumulation begins (optimal exercise intensity) will be described later.

[0060] If the point at which lactic acid accumulation begins cannot be identified (NO in step S9), the central processing unit 21 increases the load (exercise intensity) of the bicycle ergometer 10 (step S10) and has exerciser A continue exercising at that intensity.

[0061] Thereafter, until the lactic acid accumulation starting point can be identified, the central processing unit 21 repeatedly performs the following steps: identifying the HR value (step S5), calculating the LF value (step S6), creating a graph of the evaluation curve (step S7), and identifying the starting point of the first rise (step S8).

[0062] If the lactate accumulation initiation point can be identified (YES in step S9), the central processing unit 21 operates as an exercise intensity control means 21A and sets the exercise intensity of the bicycle ergometer 10 to be maintained at the exercise intensity at the lactate accumulation initiation point (optimal exercise intensity) (step S11).

[0063] Exercise participant A can continue exercising for a predetermined time at an exercise intensity set to the optimal exercise intensity (step S12).

[0064] If the measurement mode is selected in mode selection (step S3), after the lactate accumulation start point is identified, the exercise intensity that serves as a cool-down for exerciser A is maintained for a predetermined period of time, after which the bicycle ergometer 10 is stopped.

[0065] The exercise intensity control means 21A of the control device 20 sets the exercise intensity of the bicycle ergometer 10 to be equal to the exercise intensity at the lactate accumulation initiation point, and after a predetermined time has elapsed (step S12), it gradually lowers the exercise intensity of the bicycle ergometer 10 to allow exerciser A to cool down, and then stops the bicycle ergometer 10.

[0066] As described above, the exercise intensity determination system 100 according to this embodiment can detect the exercise intensity at which lactic acid accumulation begins for exerciser A, i.e., the optimal exercise intensity. By continuing to exercise at that optimal exercise intensity, exerciser A can perform optimal training.

[0067] Furthermore, if the optimal exercise intensity can be identified as the exercise intensity at which lactic acid accumulation begins, then even when exercising using exercise equipment other than the bicycle ergometer 10, the exercise state can be achieved under the optimal exercise intensity, thereby enhancing the training effect for exerciser A.

[0068] Next, we will explain a method for identifying the point at which lactate accumulation begins using an evaluation curve.

[0069] (Example 1) Figure 5 is a graph of an evaluation curve for Subject 1, with the horizontal axis representing exercise intensity (watts) and the vertical axis representing the HR / LF value, plotting the HR / LF value for each exercise intensity. Figure 6 is a line graph obtained by approximating the plots shown in Figure 5 with straight lines.

[0070] As shown in Figures 5 and 6, in the evaluation curve of Subject 1, the HR / LF value is almost 0 in the range where the exercise intensity is approximately 125 or less, and from the point where the exercise intensity exceeds 125, it increases sharply as the exercise intensity increases, and the first rising region P1 appears. The exercise intensity at which the change in the slope of HR / LF first becomes large is the starting point P of the first rising region.

[0071] After the HR / LF value increases, a region R1 appears where it temporarily decreases.

[0072] The HR / LF value temporarily decreases, and then the decrease stops when the exercise intensity is approximately 179.

[0073] Note that the decrease in HR / LF values ​​varies from person to person and differs depending on the exerciser. It may decrease by about 30% of the increase in the first rising zone P1, or it may decrease by more than 30% or less than 30%.

[0074] As the exercise intensity is further increased, the HR / LF value begins to rise sharply again, and a second rising region P2 appears. The exercise intensity at which this HR / LF value rises sharply again and the slope of the change in HR / LF shows the final maximum value is identified as the lactate accumulation initiation point S, and the exercise intensity at lactate accumulation initiation point S is determined to be the optimal exercise intensity.

[0075] In other words, 178 watts, which is the exercise intensity at the lactate accumulation initiation point S, is determined to be the optimal exercise intensity.

[0076] Prior to the exercise, a blood test was performed on Subject 1 to measure its blood lactate level, and the optimal exercise intensity based on this level was calculated in advance. The optimal exercise intensity for Subject 1, determined from its blood lactate level, was 179 watts.

[0077] The optimal exercise intensity obtained from the evaluation curves shown in Figures 5 and 6 is 178 watts. The error between this and the measured value of the optimal exercise intensity (the optimal exercise intensity for subject 1 obtained from blood tests), which is 179 watts, is calculated as follows: (179 - 178) / 179 × 100 = 0.56%

[0078] Thus, the optimal exercise intensity obtained using the evaluation curve is within an error range of less than 1% compared to the optimal exercise intensity measured from blood tests.

[0079] (Example 2) Figure 7 is a graph of the evaluation curve for Subject 2, with the horizontal axis representing exercise intensity (watts) and the vertical axis representing the HR / LF value, plotting the HR / LF value for each exercise intensity. Figure 8 is a line graph corresponding to Figure 7, similar to Figure 6.

[0080] As shown in Figures 7 and 8, in the evaluation curve of subject 2, the HR / LF value is almost 0 in the range of exercise intensity below 125, and from the point where the exercise intensity exceeds 125, it increases sharply as the exercise intensity increases, and the first rising region P1 appears. The exercise intensity at which the change in the slope of HR / LF first becomes large is the starting point P of the first rising region.

[0081] After the HR / LF value increases, a region R1 appears where it temporarily decreases.

[0082] The HR / LF value decreases by about 50% of the increase in the first rising region P1, and then the decrease stops when the exercise intensity is approximately 165.

[0083] If the exercise intensity is further increased, the HR / LF value will start to rise sharply again, and a second rising region P2 will appear. The exercise intensity at which this HR / LF value rises sharply again and the slope of the change in HR / LF shows the final maximum value is identified as the lactate accumulation initiation point S, and the exercise intensity at the lactate accumulation initiation point S is determined to be the optimal exercise intensity.

[0084] In other words, 165 watts, which is the exercise intensity at the lactate accumulation initiation point S, is determined to be the optimal exercise intensity.

[0085] Prior to the exercise, a blood test was performed on Subject 2 to measure its blood lactate level, and the optimal exercise intensity based on this level was calculated in advance. The optimal exercise intensity for Subject 2, determined from its blood lactate level, was 164 watts.

[0086] The optimal exercise intensity obtained from the evaluation curves shown in Figures 7 and 8 is 165 watts. The error between this and the measured value of the optimal exercise intensity (the optimal exercise intensity for subject 2 obtained from blood tests), which is 164 watts, is calculated as follows: (164 - 165) / 164 × 100 = 0.61%

[0087] Thus, for Subject 2, the optimal exercise intensity obtained using the evaluation curve has an error of less than 1% compared to the optimal exercise intensity measured from blood tests.

[0088] (Example 3) Figure 9 is a graph of the evaluation curve for Subject 3, with the horizontal axis representing exercise intensity (watts) and the vertical axis representing the HR / LF value, plotting the HR / LF value for each exercise intensity. Figure 10 is a line graph corresponding to Figure 9, similar to Figure 6.

[0089] There are significant individual differences in the shape of the evaluation curve, and in some cases, as with subjects 1 and 2, the lactate accumulation onset point S cannot be easily identified. Subject 3 is one such example.

[0090] As shown in Figures 9 and 10, in the evaluation curve of subject 3, the HR / LF value is almost 0 in the range of exercise intensity below 170, and from the point where the exercise intensity exceeds 170, it increases sharply as the exercise intensity increases, and the first rising region P1 appears. The exercise intensity at which the change in the slope of HR / LF first becomes large is the starting point P of the first rising region.

[0091] In the evaluation curves of subjects 1 and 2, as the exercise intensity is further increased, a decreasing region R1 appears after the first rising region P1. However, in the evaluation curve of subject 3, the decreasing region R1 does not appear, and the HR / LF value remains almost constant.

[0092] This plateauing region Q continues until the exercise intensity reaches approximately 198. Once the exercise intensity exceeds approximately 198, the HR / LF value begins to rise sharply again, and a second rising region P2 appears. The exercise intensity at which the HR / LF value rises sharply again and the slope of the change in HR / LF shows its final maximum value is identified as the lactate accumulation initiation point S, and the exercise intensity at the lactate accumulation initiation point S is determined to be the optimal exercise intensity.

[0093] In other words, 198 watts, which is the exercise intensity at the lactate accumulation initiation point S, is determined to be the optimal exercise intensity.

[0094] Prior to the exercise, a blood test was performed on Subject 3 to measure its blood lactate level, and the optimal exercise intensity based on this level was calculated in advance. The optimal exercise intensity for Subject 3, determined from its blood lactate level, was 200 watts.

[0095] The optimal exercise intensity obtained from the evaluation curves shown in Figures 9 and 10 is 198 watts. The error between this and the measured value of the optimal exercise intensity (the optimal exercise intensity for subject 3 obtained from blood tests), which is 200 watts, is calculated as follows: (200 - 198) / 200 × 100 = 1.00%

[0096] Thus, the optimal exercise intensity obtained using the evaluation curve is within an error range of less than 1% compared to the optimal exercise intensity measured from blood tests.

[0097] As described above, in all three subjects (1, 2, and 3), the optimal exercise intensity values ​​obtained from the evaluation curves were within an error of 1.0% or less from the measured values. These test results for subjects 1, 2, and 3 demonstrate that the exercise intensity determination system 100 can detect the optimal exercise intensity for exerciser A with extremely high accuracy.

[0098] The exercise intensity determination system 100 according to this embodiment is not limited to the structure described above, and various modifications are possible.

[0099] The vertical axis of the evaluation curve can use the value of 1 / LF instead of the HR / LF value.

[0100] Figure 11 is a graph of the evaluation curve for Subject 2 shown in Figure 7, but with the 1 / LF value used on the vertical axis instead of the HR / LF value.

[0101] Since the evaluation curve shown in Figure 11 shows a similar trend to the evaluation curve shown in Figure 7, by using the 1 / LF value instead of the HR / LF value, the process of measuring the HR value can be omitted, thus simplifying the process of creating the evaluation curve graph.

[0102] In the exercise intensity determination system 100, the heart rate monitor 30 and the control device 20 are connected via a wired connection cable 32, but it is also possible to connect them using Bluetooth® or other wireless communication means.

[0103] Alternatively, instead of the heart rate monitor 30, a pulse wave detection device capable of detecting pulse waves can be used. From the pulse wave data detected by the pulse wave detection device, the heart rate value (HR) can be calculated, and further, the value of LF, which is the integral value of the low-frequency component obtained by power spectral analysis of the heart rate variability frequency, can be calculated.

[0104] By using a pulse wave detection device, HR and LF values ​​can be detected from anywhere on the exerciser's body.

[0105] (Second Embodiment) In the first embodiment described above, the value of the exercise intensity of the bicycle ergometer (exercise equipment) 10 is used as the value on the horizontal axis of the evaluation curve graph. However, it is possible to use a value obtained by logarithmically transforming the exercise intensity instead of the exercise intensity value.

[0106] Figures 12, 13, and 14 show the evaluation curves when the horizontal axis of the evaluation curves shown in Figures 5, 7, and 9 is the value obtained by logarithmically transforming the exercise intensity.

[0107] For example, comparing Figure 5 and Figure 12 for Subject 1, it is easier to identify the starting point of the rise in the second rising region P2, i.e., the lactate accumulation initiation point S, in Figure 12 than in Figure 5.

[0108] In this way, by using the logarithmically transformed value of exercise intensity as the horizontal axis of the evaluation curve graph, the lactate accumulation initiation point S and, consequently, the value of the optimal exercise intensity can be identified with greater accuracy.

[0109] By using a graph of an evaluation curve with the logarithmically transformed exercise intensity on the horizontal axis, it is possible to employ a method different from the method for determining the lactate accumulation initiation point S shown in the first embodiment.

[0110] Figure 15 is a graph of an evaluation curve showing a second method for determining the lactate accumulation initiation point S.

[0111] This second method comprises the following steps: (1) The change in HR / LF within a sufficiently narrow range of exercise intensity (exercise work rate) (a predetermined exercise intensity interval, which can be set to, for example, 1 watts to 10 watts, preferably 1 watts) is calculated as the slope of the regression line (regression analysis). (2) This calculation is then repeated three times (a total of four times). (3) The exercise intensity at which the slope obtained from the fourth regression analysis shows the maximum value is identified as the exercise intensity at the lactate accumulation initiation point S where HR / LF rises sharply and does not decrease thereafter.

[0112] Figure 15(A) is a graph of the exerciser's evaluation curve, with the vertical axis representing the HR / LF value and the horizontal axis representing logarithmically transformed exercise intensity (exercise work rate: unit is watts).

[0113] Figure 15(B) shows the evaluation curve obtained by performing the first regression analysis on the evaluation curve shown in Figure 15(A).

[0114] Figure 15(C) shows the evaluation curve obtained by performing a second regression analysis on the evaluation curve shown in Figure 15(B).

[0115] Figure 15(D) shows the evaluation curve obtained by performing a third regression analysis on the evaluation curve shown in Figure 15(C).

[0116] Figure 15(E) shows the evaluation curve obtained by performing a fourth regression analysis on the evaluation curve shown in Figure 15(D).

[0117] In the evaluation curve obtained from the fourth regression analysis shown in Figure 15(E), the rising region with the maximum value W of the HR / LF value is the second rising region, the starting point of the rise is the lactate accumulation initiation point S, and the exercise intensity at the lactate accumulation initiation point S is the optimal exercise intensity.

[0118] Thus, by using a regression line, it is possible to identify the starting point S of lactic acid accumulation.

[0119] In the second method described above, the horizontal axis of the evaluation curve graph uses the logarithmically transformed value of exercise intensity. However, as in the first embodiment, it is also possible to use the unlogarithmically transformed value of exercise intensity as the horizontal axis.

[0120] A Exerciser 10 Bicycle ergometer 11 Control signal cable 12 Monitor 20 Control device 21 Central processing unit 21A Exercise intensity control means 21B HR determination means 21C LF calculation means 21D Evaluation curve generation means 21E Ascent start point identification means 21F Exercise intensity identification means 22 First memory 23 Second memory 24 Input interface 25 Output interface 26 Bus 27 Display screen 30 Heart rate monitor 31 Electrodes 32 Connection cable 33 Heart rate information 34 Control signal 100 Exercise intensity determination system S Lactate accumulation start point

Claims

1. A method for determining the exercise intensity at which lactic acid accumulation begins for an exerciser using an exercise equipment with variable load, comprising: increasing the exercise intensity of the exercise equipment; identifying the value of HR, which is the exerciser's heart rate at a predetermined exercise intensity; calculating the value of LF, which is the integral value of the low-frequency component obtained from the exerciser's heart rate variability frequency at the predetermined exercise intensity; generating an evaluation curve with the exercise intensity on the horizontal axis and HR / LF on the vertical axis; and calculating the slope of the amount of change in HR / LF for each predetermined exercise intensity interval in the evaluation curve, and identifying the exercise intensity at which the slope shows the maximum value as the exercise intensity at which lactic acid accumulation begins.

2. The method for determining the exercise intensity at the lactate accumulation initiation point according to claim 1, characterized in that the exercise intensity is determined by repeatedly applying a predetermined regression analysis to the evaluation curve for each exercise intensity interval, and identifying the exercise intensity at which the value obtained from the final regression analysis is maximized as the exercise intensity at the lactate accumulation initiation point.

3. The method for determining the exercise intensity at the point where lactic acid accumulation begins, according to claim 1, characterized in that the horizontal axis of the evaluation curve is the value obtained by logarithmically transforming the exercise intensity, instead of the exercise intensity itself.

4. The method for determining the exercise intensity at the lactate accumulation initiation point according to claim 1, characterized in that the vertical axis of the evaluation curve is 1 / LF instead of HR / LF.

5. A program for causing a computer to perform the method according to any one of claims 1 to 4.

6. An exercise intensity determination system for determining the exercise intensity at which lactate accumulation begins for an exerciser using an exercise equipment with variable load, comprising: exercise intensity control means for controlling the exercise intensity of the exercise equipment; HR determination means for determining the value of HR, which is the heart rate of the exerciser at a predetermined exercise intensity; LF calculation means for calculating the value of LF, which is the integral value of the low-frequency component obtained from the heart rate variability frequency of the exerciser at the predetermined exercise intensity; evaluation curve generation means for generating an evaluation curve with the exercise intensity on the horizontal axis and HR / LF on the vertical axis; and exercise intensity identification means for calculating the slope of the amount of change in HR / LF for each predetermined exercise intensity interval in the evaluation curve, and identifying the exercise intensity at which the slope shows the maximum value as the exercise intensity at which lactate accumulation begins.

7. The exercise intensity determination system according to claim 6, characterized in that the exercise intensity determination means repeatedly applies regression analysis for each predetermined exercise intensity interval to the evaluation curve, and identifies the exercise intensity at which the value obtained from the final regression analysis is maximum as the exercise intensity at which lactic acid accumulation begins.

8. The exercise intensity determination system according to claim 6, characterized in that the horizontal axis of the evaluation curve is the value obtained by logarithmically transforming the exercise intensity, instead of the exercise intensity itself.

9. The exercise intensity determination system according to claim 6, characterized in that the vertical axis of the evaluation curve is 1 / LF instead of HR / LF.

10. An exercise device incorporating an exercise intensity determination system according to any one of claims 6 to 9, wherein the exercise intensity control means maintains the exercise intensity of the exercise device at the exercise intensity at the lactate accumulation initiation point after the exercise intensity at the lactate accumulation initiation point has been identified.

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