JP2007236663A - Method and device for evaluating muscular fatigue, and exercise support system reflecting physiological situation of user in real-time - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for evaluating muscular fatigue by estimating the internal situation of a human body through the use of the angle of joints in doing exercise and mechanical amounts outside of the human body such as floor reactive force, and to provide a device therefor, and a safe and effective exercise support system using the method and device. <P>SOLUTION: The muscular fatigue evaluating method is the method for calculating muscular stress by using the angle θ of the joints, which is obtained via a sensor mounted on a user and the floor reactive force F, and integrating the obtained muscular stress within a time range from a measurement start till a measurement end by using the sensor. The evaluating method and the system using the method and the device are provided. The calculation is performed based on an expression; F<SB>ce</SB>=k(V<SB>ce</SB>, L<SB>ce</SB>)(q-αf<SB>fatigue</SB>(∫F<SB>ce</SB>dt)), where F<SB>ce</SB>is the force of a contraction element in muscle, V<SB>ce</SB>is the contraction speed of the contraction element, L<SB>ce</SB>is the length of the contraction element, q is excitement standard, α is a parameter by each muscle, k is the speed-force relational expression of the muscle to be determined by each muscle, and f<SB>fatigue</SB>is an integration muscular potential fatigue characteristic expression. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an evaluation of muscle fatigue using a computer and an exercise support system that reflects a user's physiological situation in real time using the result, and in particular, a joint angle and floor reaction corresponding to a user's exercise site. The present invention relates to a method for calculating a muscle fatigue level of a user by exercise from force data using a computer, an apparatus therefor, and an exercise support system that reflects a user's physiological situation using the same in real time.

  Traditionally, rehabilitation has been advised and directed by physical therapists, but because the physical therapists have a large burden, today's aging society and high welfare society have not been able to adequately answer demand. It's real. Therefore, development of medical devices not only for conventional health promotion devices but also for rehabilitation that requires more advanced technology is desired. In other words, in the case of a device for health promotion, the optionality of the performance required for the device can be widely accepted. However, in the case of a device for a weak person different from a healthy person, the user's condition is It is desirable to be able to cope with this, and the requirement for safety becomes more severe.

Conventionally, from the viewpoint of ensuring safety, a method has been employed in which the body is prevented from falling by performing an operation in a supine position, or the degree of freedom of the body is restrained to some extent using a harness or the like (Patent Documents 1-4) ), The device itself had to be increased in size. Until now, the idea of adjusting the device according to the situation inside the human body has not been proposed. However, if the information inside the user's human body can be easily estimated and the estimated information can be reflected on the device in real time, the effect of rehabilitation or the like should be maximized.
JP 2000-102576 A JP 2005-192695 A Japanese Patent Laid-Open No. 2005-211086 Japanese Unexamined Patent Publication No. 2005-211328

Therefore, the first object of the present invention is to provide a method for estimating the degree of muscle fatigue by estimating the internal conditions of the human body using various physical quantities outside the human body, such as the joint angle and floor reaction force during exercise. It is in.
The second object of the present invention is to convert information inside the human body into data using the various physical quantities outside the human body such as the joint angle and floor reaction force during exercise, and to evaluate the degree of muscle fatigue Is to provide.
Furthermore, a third object of the present invention is to exercise the user's situation in real time and the user's physiological situation in real time so that the exercise can be exercised safely and effectively. To provide a support system.

As a result of diligent research to achieve the above-mentioned objectives, the present inventors have made calculation by a computer using a specific calculation formula, so that the joint angle, which is a mechanical quantity outside the human body, and the floor reaction force can be obtained. The present inventors have found that the user's muscle fatigue level can be estimated and arrived at the present invention.
That is, the present invention calculates the muscle tension using the joint angle θ and the floor reaction force F obtained through a sensor attached to the user, and then measures the obtained muscle tension from the start of measurement using the sensor. A method for evaluating the degree of muscle fatigue that integrates in the time range until the end, wherein the calculation is performed based on the following general formula (1), and is used for the evaluation method It is an exercise support system that reflects a user's physiological situation using the apparatus and its evaluation method in real time.
General formula (1)
In the present invention, it is preferable to employ each angle of ankle joint, knee joint, and hip joint as the joint angle. If the upper body is a relevant part, the main joint angles up to that part must be entered. If the corresponding part is close to the lower end of the lower body, the knee and hip angles are not necessarily required. Further, a more detailed result can be obtained by making the human body model in detail and increasing the number of joints to be input. In order to ensure safety, it is preferable to provide a safety device so that the exercise device stops when the set muscle fatigue level is reached.

  According to the present invention, the degree of muscle fatigue is estimated using a mechanical quantity outside the human body, so that it is easy and does not place a burden on the user, and the obtained data is reflected in the exercise device in real time. Therefore, it is easy to obtain the maximum effect safely.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a conceptual diagram of an embodiment of the present invention. In the figure, reference numeral 1 is an exercise tool for forcibly walking a user having a foot, knee, hip joint angle and floor reaction force detection sensor, and reference numeral 2 is used based on each obtained joint angle and floor reaction force. A computer 3 for calculating the muscle tension and muscle fatigue of the person is a control unit for reflecting the calculated muscle fatigue on the carrying tool and controlling the movement of the user.

In the present invention, the angles between the user's skeletons are measured, and these angles are input to a human body model having a human skeleton embedded in a computer to solve the multisystem problem, and then the obtained joint moment Is applied to a muscle model including the following general formula (1), the user's muscle tension is determined using an optimization method, and finally the muscle fatigue level is calculated from this muscle tension (see FIG. 2).
General formula (1)

For example, when the muscles of the lower limbs during walking are the target region, the posture of the human body model in the computer having a human skeleton is uniquely determined by designating each angle of the foot, knee, and hip joint. be able to. Therefore, if the joint angles θ _foot , θ _knee , θ _hip of the user are detected by a sensor attached to the exercise tool worn by the user and are input to the computer, the human body model in the computer is the same as that of the user. I will take a posture. In addition, as said sensor, it can select from a well-known sensor suitably and can be used.

The mass of each part of the human body model in the computer is set according to the user, and the gravity applied to the human body model is automatically calculated, so that the human body model is subjected to the same load as the user. In addition to this, if an external force received from a point where the user's body comes into contact with the outside is input, the mechanical state of the human body model becomes the same as that of the user. In the case of walking, the only point where the user including the equipment is in contact with the outside is the contact point between the sole of the foot and the floor. By inputting the left and right floor reaction forces F _r and F _l , The target state can be reproduced in the computer 2.

  Since the human body model in the computer 2 reflects the movement of the user, each muscle tension and muscle fatigue level at each time step can be output. Although FIG. 1 has an output screen for outputting results, it is natural that a printer for printing out may be further included. A system flow for calculating muscle tension and muscle fatigue from each joint angle θ and floor reaction force F is shown in FIG.

(About the human body model)
Assuming each part of the human body is a rigid body with an appropriate mass and moment of inertia, and considering each joint as a mechanical joint with the same degree of freedom and function, the human body is mathematically represented as a collection of a series of rigid bodies. The problem of obtaining the force and torque generated at each joint during exercise can result in an inverse dynamics problem for many systems. Therefore, it is impossible to non-invasively measure the mass and moment of inertia of each part, but according to past studies and statistical approaches, it is possible to obtain estimates from height and weight ( Non-patent document 1).
Tsuyoshi Ae, Takashi Yokoi: Estimation of body part inertia characteristics of Japanese athletes Biomechanism 11, 23-33 University of Tokyo Press

Moreover, in the field of mechanics, arbitrary functions in each joint have been mathematically expressed. For example, the human elbow and knee joints can sufficiently estimate the behavior during a large displacement movement such as walking or throwing even if it is assumed to be a rotary joint with only a single degree of freedom of rotation. Is known (Non-Patent Document 2).
Nobutoshi Yamazaki, Kazunori Hase: Biomechanical determination criteria for pace and step length in free walking Biomechanism 11,179-189 University of Tokyo Press

(Example of constraint type: Rotation constraint, acceleration type)
A rotary joint that only allows rotation around an axis in a two-dimensional plane is mathematically
It can be expressed as. Where r is the translational coordinate of each rigid body, s is a vector from the center of the rigid body to the constraint center of the joint, and the subscripts i and j represent the two rigid bodies connected by the joint. The objects i and j connected by the rotary joint must always move within a range that satisfies this equation.

  Moreover, a constraint equation (speed equation) relating to speed can be obtained by partial differentiation of this equation with respect to time. The velocity equation is an equation for the velocity that the rigid body connected by the rotating joint must satisfy during movement. Further, by further differentiating the velocity equation, the acceleration equation can be similarly obtained.

The three-dimensional rotational constraint formula is
It is expressed. Φ ^s in the equation is similar to the two-dimensional rotation constraint equation, and means that the joint centers P _i and P _j on the rigid bodies i and _j are the same point. Φ ^pl means that the rotation axes h _i and h _j defined by both _i and _j are always parallel. A conceptual diagram is shown in FIG. Specifically, each of Φ ^s and Φ ^pl is expressed as follows.
In the above formula, A is a coordinate transformation matrix for transforming each rigid body to the global coordinate system, h is a vector that defines the rotation direction of the joint shown in the figure, and f and g are orthogonal to the vector h with point P as the origin. It is a vector that forms a joint coordinate system.

By specifying the joint angle for each time in addition to the joint constraint formula, the joint state at each time can be uniquely determined. The joint angle information to be input is called driver restraint.
It is represented by Even in three dimensions, the velocity equation and the acceleration equation can be obtained by differentiating the constraint equation with respect to time.
In the actual program, constraint equations, velocity equations and acceleration equations are algebraically libraryized, calculated by inputting the state quantities of the related objects, and by directly calculating without time differentiation, It is processed at high speed.

(Equation of motion)
When each joint of the human body is expressed by a constraint equation Φ _i (i = 0,1, Λnj) (nj is the number of joints),
Newton-Euler equation of motion is
It can be expressed as. In the equation, M is a diagonal matrix having the mass of each part of the human body as a diagonal component, and J ′ is a diagonal matrix having the inertial moment around the local coordinate system of each part as a diagonal component. Indicates that the target is the local coordinate system. Φ _r and Φ _{π ′} are a constraint equation regarding the degree of freedom of translation and a constraint equation regarding the degree of freedom of rotation of the local coordinate system expressed by Euler angles, respectively.

  The second [] on the left side is a variable matrix, r is the acceleration in the translation direction of each part, ω ′ is the angular acceleration in the local system, and λ is a Lagrange multiplier that links the equation of motion and the acceleration equation. In inverse dynamics analysis, the force and torque generated in each joint can be determined by obtaining this λ.

F ^にお^{け る} in the right-hand side matrix represents the generalized external force. The generalized external force represents an external force acting on the system in the local coordinate system of each part that acts. The two items represent generalized torque, and ^N′Α is the external torque acting from the outside. Further, γ is the above-described acceleration formula obtained from each constraint formula.

(About the solution)
Since the coefficient matrix on the left side is a symmetric matrix and the vector on the left side is determined from various conditions input to the model, the above equation of motion can be solved by the Gaussian elimination method, the LU decomposition method, or the like. When the Lagrange multiplier vector λ is determined, the restraining reaction force and reaction torque generated at each joint are
It can be expressed as. “” ”In the expression indicates that these expressions are expressed in the joint coordinate system. C represents a coordinate conversion matrix from a joint coordinate system to a related object, and the superscript “˜” represents a distortion matrix.

By using the construction of the human body model and the designation and solution of the motion described above, the joint reaction force and joint torque during the motion can be calculated. This method is based on multi-body dynamics (Non-Patent Document 3), and the obtained joint torque is the sum of torques generated around the joint due to muscle tension of a plurality of muscles. It is known that the muscle tension of each muscle can be estimated by solving the joint torque by an optimization method using a muscle model having appropriate parameters for each muscle (Non-Patent Document 4).
EJ Haug: Fundamentals of Computer-Based Mechanism Analysis, 1996, Taiga Publishing Kazunori Hase, Nobutoshi Yamazaki (1995): Development of a general-purpose three-dimensional musculoskeletal model.

(About muscle model)
The muscle tension generated by each muscle around the joint when the joint torque obtained from the human body model is input can be estimated by an optimization method using an appropriate muscle model. The following general formula (1) is a muscle model having fatigue characteristics used by the present inventors.
In the formula, F _ce is the contraction element force of the muscle, V _ce is the contraction speed of the contraction element, L _ce is the contraction element length, q is the excitement level, and α is a parameter for each muscle. k is the muscle speed-force relationship, and when the contraction element contracts
FACTOR = Min (1,3.33 ・ q)
It is expressed. Here, A _rel and B _rel take values around 0.4 and 5.0, respectively, and V _ce is a value obtained by dividing the contraction element speed by the contraction element length.

The relationship between force and speed at the time of expansion of the contraction element is as follows.
It can be expressed as Here, F _asympt (asymptotic level of the exertion tension) and Slopefactor (ratio of the slope of the extension part and the contraction part of the force-speed curve at zero speed) are parameters, and should be values around 1.5 and 2.0, respectively. It is reasonable.

On the other hand, in the high extension speed part
It can be expressed as Here, Slopelin is a parameter that defines the relationship between force and speed in the high extension speed portion, and takes a value around 200. The boundary between the low speed part and the high speed extension part
This is the point. Many studies have been made on the mechanical properties of the above muscles (Non-Patent Documents 5 to 7).
Hill AV (1938): The heat of shortening and the dynamic constants of muscle.Proceedings of the Royal Society of London, Series B 126: 136-195 Felix E. Zajac (1989): Muscle and Tendon: Properties, Models, Scaling And Application to Biomechanics and Motor Control, Critical Reviews in Biomedical Engineering Volume 17, Issue 4: 359-411 Nagano and Gerritsen (2001): Effect of neuromuscular strength training on vertical jumping performance-a computersimulation study.Journal of Applied Biomechanics 17: 113-128

(About fatigue properties)
F _fatigue in the general formula (1) is a surface myoelectric potential-fatigue characteristic derived by the present inventors through experiments,
f _fatigue = m [(-5.0y + 9.0) × 10 ^-8・ x ³ + (2.0y-4.0) × 10 ^-5・ x ² + (-2.2y + 5.9) × 10 ^-3・ x + 0.3] + E
It is expressed. In the equation, m is a parameter determined for each muscle, x is an integral value of the force generated by the muscle from the start of exercise to the current time (∫F _ce dt), y represents the cycle of motion [second], E is This represents a correction term for reducing an error when the period is near zero.

The above-mentioned f _fatigue is determined by changing the exercise conditions during repetitive exercise under light load, observing changes in integrated muscle potential (iEMG) accompanying fatigue, and regressing the obtained muscle fatigue characteristics data. It is a potential rise characteristic formula. This formula uses the integrated value from the start of exercise as an argument when calculating muscle tension, and adds fatigue characteristics to the muscle contraction element model as expressed by the general formula (1). Is a formula not described in the literature, which is derived for the first time by the present inventors.

  The apparatus for carrying out the above-described muscle fatigue evaluation method of the present invention is a means capable of measuring the joint angle θ and the floor reaction force of the place where the user wears the device, the θ, F, and the general It comprises means for calculating the user's muscle fatigue level using equation (1) and output means for outputting the calculated muscle fatigue level (see FIG. 1).

  As a means for measuring the joint angle θ and the floor reaction force, a sensor appropriately selected from known sensors can be used, and the device can be movable, but it can be used as a simple step. Or can be made non-movable using a forced walking device such as a treadmill (see FIG. 6). The means for calculating the muscle fatigue level of the user using the measured θ, F and the general formula (1) includes an input means for inputting θ and F, such as a keyboard, and the general formula (1). The output means for outputting the calculated muscle fatigue is a variety of displays and / or printers that can be displayed as images.

The exercise support system of the present invention includes (1) an exercise device such as a computer-controllable treadmill for forcibly exercising the user, and (2) a user-mounted exercise device such as a joint angle θ and a floor reaction at a desired location. An exercise support system comprising measurement means for measuring force F and (3) means for calculating muscle fatigue using the obtained data of θ and F. In particular, by inputting the data on the muscle fatigue level to the computer control unit of the exercise device (1), the forced exercise of the exercise device is controlled to reflect the muscle fatigue level of the user. As described above, the exercise support system according to the present invention is the exercise support system that reflects the physiological state of the user in real time. Thus, by using the exercise support system of the present invention, it is possible to support exercise such as rehabilitation safely and efficiently within a range that is not unreasonable for the user. In order to further enhance safety, it is preferable to provide a safety device so that the fatigue level allowed by the user is set in advance and the exercise system automatically stops when the value is reached.
Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

Example Muscle fatigue during walking was estimated as follows using a muscle model represented by the general formula (1) and a human body model including the muscle model.
The surface myoelectric potential when walking on a treadmill at a speed of 4 km / h for 10 minutes and the walking data (each joint angle, floor reaction force), which is synchronized with the walking at that time (T ≒ 1 second), Fatigue level was estimated by simulation by inputting the calculation program of Equation (1) into the installed computer. The surface myoelectric potential was measured for the inner vastus muscle. FIG. 5 shows the positions of the electrodes for measurement, and FIG. 6 shows the arrangement of the electrodes and electromyographs at the time of measurement. The comparison between the estimation result and the experimental value is as shown in FIG.

  In the method for evaluating muscle fatigue according to the present invention, the degree of muscle fatigue of the user due to exercise is calculated from the joint angle and floor reaction force data corresponding to the user's exercise site using a computer. In addition, since the device becomes smaller, it is extremely meaningful in industry. In addition, since the system of the present invention reflects the user's situation in real time, it has a great advantage that it is safe and the support efficiency is improved.

It is explanatory drawing for demonstrating the structure of this invention. It is a routine flow for calculating muscle fatigue. It is a model figure of a rotation joint. It is the graph which compared the result of the simulation using this invention, and the measured value of myoelectric potential. It is a figure which shows an electrode position when a myoelectric potential is measured in an Example. It is a figure which shows arrangement | positioning of the measuring device in an Example.

Explanation of symbols

1 Equipment 2 Computer that calculates fatigue 3 Control unit

Claims (8)

The muscle tension is calculated using the joint angle θ and the floor reaction force F obtained through the sensor attached to the user, and the time range from the start of measurement using the sensor to the end of the measurement of the obtained muscle tension is then calculated. A method for evaluating the degree of muscle fatigue, wherein the calculation is performed based on the following general formula (1):
General formula (1)
In the general formula (1), F _ce is the contraction force of the muscle, V _ce is the contraction speed of the contraction element, L _ce is the contraction element length, q is the excitement level, and α is a parameter for each muscle. K is a muscle speed-force relational expression determined for each muscle, and f _fatigue is an integral muscle potential fatigue characteristic expression.   2. The muscle fatigue evaluation method according to claim 1, wherein the joint angles are angles of an ankle joint, a knee joint, and a hip joint. When k is contracted,
(However, FACTOR is Min (1,3.33 · q), and V _ce is a value obtained by dividing the contraction element velocity by the contraction element length.)
In particular, in the high extension speed part,
(Where Slopelin is a parameter that defines the relationship between force and speed in the high stretch rate portion). 3. The method for evaluating the degree of muscle fatigue according to claim 1 or 2. The method for evaluating the degree of muscle fatigue according to any one of claims 1 to 3, wherein the f _fatigue is represented by the following formula;
f _fatigue = m [(-0.5y + 9.0) × 10 ^-8・ x ³ + (2.0y-4.0) × 10 ^-5・ x ² + (-2.2y + 5.9) × 10 ^-3・ x + 0.3] + E
Here, m represents a parameter determined for each muscle, x represents ∫F _ce dt, and y represents a motion period (second). E is a correction term for reducing the error when the period is near zero. A means of measuring the joint angle θ and floor reaction force of the place where the user wears it, and calculating the degree of muscle fatigue of the user using the θ, F and the following general formula (1) Means and an output means for outputting the calculated muscle fatigue level;
General formula (1)
In the general formula (1), F _ce is the contraction force of the muscle, V _ce is the contraction speed of the contraction element, L _ce is the contraction element length, q is the excitement level, and α is a parameter for each muscle. Further, k is a muscle speed-force relational expression determined for each muscle, and f _fatigue is an integral myoelectric potential fatigue characteristic expression, which is expressed as follows.
(However, FACTOR is Min (1,3.33 · q), and V _ce is a value obtained by dividing the contraction element velocity by the contraction element length.)
In particular, in the high extension speed part,
(Here, Slopelin is a parameter that defines the relationship between force and speed in the high extension speed section.), And f _fatigue is expressed as follows.
f _fatigue = k [(-0.5y + 9.0) × 10 ^-8・ x ³ + (2.0y-4.0) × 10 ^-5・ x ² + (-2.2y + 5.9) × 10 ^-3・ x + 0.3] + E
Here, x represents ∫F _ce dt, and y represents the period of motion (seconds). E is a correction term for reducing the error when the period is near zero.   (1) a computer-controlled exercise device for forcibly exercising the user; (2) a measurement means for measuring the joint angle θ and the floor reaction force F at a desired location by attaching the user to the user; (3) obtained And a means for calculating muscle fatigue using the θ and F data, wherein the muscle fatigue data is input to the computer controller of the exercise device (1). An exercise support system that reflects a user's physiological condition in real time, wherein forced exercise of the exercise device is controlled to reflect the degree of muscle fatigue of the user. 5. The exercise support system that reflects a user's physiological situation in real time according to claim 4, wherein the calculation of the muscle fatigue level is performed using the following general formula (1).
General formula (1)
In the general formula (1), F _ce is the contraction force of the muscle, V _ce is the contraction speed of the contraction element, L _ce is the contraction element length, q is the excitement level, and α is a parameter for each muscle. Further, k is a muscle speed-force relational expression determined by the muscle, and f _fatigue is an integral myoelectric potential fatigue characteristic expression, which are expressed as follows, respectively.
(However, FACTOR is Min (1,3.33 · q), and V _ce is a value obtained by dividing the contraction element velocity by the contraction element length.)
In particular, in the high extension speed part,
(Here, Slopelin is a parameter that defines the relationship between force and speed in the high stretch rate part), and f _fatigue is expressed as follows:
f _fatigue = k [(-0.5y + 9.0) × 10 ^-8・ x ³ + (2.0y-4.0) × 10 ^-5・ x ² + (-2.2y + 5.9) × 10 ^-3・ x + 0.3] + E
Here, x represents ∫F _ce dt, and y represents the period of motion (seconds). E is a correction term for reducing the error when the period is near zero. 8. The exercise support system for reflecting a user's physiological condition in real time according to claim 6 or 7, wherein a safety device is provided so that the exercise device stops when a set degree of muscle fatigue is reached.