A method for dynamically adjusting a swimming position according to a hip joint

Abstract

The application provides a method for dynamically adjusting swimming posture according to hip joints, comprising the following steps: S1, obtaining physical sign data of a target athlete; S2, obtaining three-dimensional swimming posture action data of the target athlete through a waterproof level motion sensor; S3, collecting high-speed images of the swimming posture of the target athlete through a camera, and performing calibration operation on the underwater camera to obtain parameters of the underwater camera; S4, obtaining displacement data, four-limb dynamic data and hip joint dynamic data of the target athlete according to the three-dimensional swimming posture action data and the high-speed images of the swimming posture; S5, calculating actual swimming posture data; S6, presetting standard swimming posture data and calculating a difference value; and S7, obtaining swimming posture correction data according to the difference value; the application can correct the swimming posture of the athlete according to the dynamic data change of the hip joints and the cooperation relationship with the four limbs when the athlete is swimming.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sports science and technology, in particular, to a method for adjusting swimming posture according to hip joint dynamics. BACKGROUND

[0002] Swimming is a common sport in life and competitive sports. When ordinary people swim, they often focus on the coordination of hand movements or leg movements, the force or speed of water striking, which is actually a misunderstanding of swimming. Since ordinary people do not have in-depth study on professional swimming skills, they are likely to overlook the importance of the hip joint to swimming speed. If the lower body only relies on the calf or thigh to strike the water, the water walking effect is actually limited. If the hip and leg can be coordinated, the power of the gluteus muscle can be mobilized, and the overall swimming speed can be greatly improved. No matter what swimming posture, the stability of the hip position is very important. For example, when breaststroke, if the hip position can be kept stable, the leg movement and hand movement can be combined best, and the unnecessary physical consumption of breaststroke in water resistance can be greatly reduced. For example, when freestyle, if the hip can be kept stable, the hip can be maintained at a high position, closer to the water surface, making swimming very easy, and more conducive to hip power driving whip leg to achieve better water walking effect. The stability of the hip can also provide stability for the rapid arm swing of the shoulder joint. In long-distance swimming, the hip can fully mobilize the muscle power of the hip, greatly reducing the burden of arm swimming, and producing a better overall swimming rhythm.

[0003] Due to the above reasons, professional swimmers pay special attention to the importance of hip joint coordination with the whole body, and the coaching team also emphasizes the importance of hip joint coordination with the whole body in daily training. However, since the athletes are training in the water, and the dynamics of the hip joint is not as easy to observe as the dynamics of the hands and feet, it is difficult for athletes to perceive whether their hip joint dynamics meet the standards set by the coaching team during intense swimming. The coaching team cannot directly observe whether the hip joint and the whole body are reasonably coordinated when the athletes are in the water, which is a great challenge in swimming posture correction, training evaluation, targeted training, and tactical research. SUMMARY

[0004] The present application solves the problem of providing a method for adjusting swimming posture according to hip joint dynamics, which can correct the swimming posture of athletes according to the dynamic data changes of the hip joint and the coordination with the limbs when the athletes swim.

[0005] To solve the above problems, the present application provides a method for adjusting swimming posture according to hip joint dynamics, comprising the following steps:

[0006] S1, analyze the physical signs of the target athlete to obtain physical sign data of the target athlete;

[0007] S2, attach waterproof level motion sensors to the target athlete, the number of waterproof level motion sensors located at the hip is H, the number of waterproof level motion sensors located at the limbs is L, H≥2L, the waterproof level motion sensors are used to obtain three-dimensional swimming posture motion data of the target athlete;

[0008] S3, synchronously collect swimming posture high-speed images above and under water of the target athlete when swimming through underwater cameras and above-water cameras, and calibrate the underwater cameras to obtain parameters of the underwater cameras;

[0009] S4, obtain displacement data, limb dynamic data, and hip joint dynamic data of the target athlete according to the three-dimensional swimming posture motion data and the swimming posture high-speed images;

[0010] S5, calculate speed data, limb dynamic power data, and hip joint dynamic power data of the target athlete according to the three-dimensional swimming posture motion data and the swimming posture high-speed images, and obtain actual swimming posture data in combination with the physical sign data;

[0011] S6, preset standard swimming posture data, calculate the Euclidean distance between each discrete point data in the actual swimming posture data and each discrete point data in the standard swimming posture data to obtain a difference value;

[0012] S7, obtain swimming posture correction data according to the difference value.

[0013] Further, in step S1, the physical sign data of the target athlete is obtained by using multi-frequency bioelectrical impedance measurement.

[0014] Further, in step S2, the waterproof level motion sensors include waterproof level myoelectric sensors and inertial measurement units with a waterproof level of ipx7.

[0015] Further, in step S3, the underwater cameras are distributed on the left and right sides, the bottom wall, and the start and finish point side walls of the swimming lane where the target athlete is located.

[0016] Further, in step S3, the underwater cameras are calibrated to obtain the parameters of the underwater cameras, which specifically include the following steps:

[0017] S31, cut the underwater swimming posture high-speed images into swimming posture images at different times;

[0018] S32, preset a fixed-size Zhang Zhengyou checkerboard calibration board and a world coordinate system origin, detect feature points in the swimming posture images, and obtain pixel coordinate values and physical coordinate values of each corner point on the Zhang Zhengyou checkerboard calibration board according to the feature points;

[0019] S33, according to the relationship between the pixel coordinate values and the physical coordinate values of the corner points of the Zhang Zhengyou chessboard calibration board, the internal parameter matrix and the external parameter matrix of the underwater camera are solved;

[0020] S34, the radial distortion coefficient of the underwater camera is calculated;

[0021] S35, the internal parameter matrix, the external parameter matrix and the radial distortion coefficient are optimized by using the Levenberg-Marquardt method.

[0022] Further, in step S5, the specific steps of calculating the four-limb dynamic power data are as follows:

[0023] S51, according to the four-limb dynamic data, the thrust F1 of the four limbs against water at different times is calculated;

[0024] S52, according to the four-limb dynamic data, the total moving distance S1 of the four limbs in water at different times is calculated;

[0025] S53, the work operation is performed according to the thrust F1 and the total moving distance S1 at different times to obtain the four-limb dynamic power data.

[0026] Further, in step S5, the specific steps of calculating the hip joint dynamic power data are as follows:

[0027] S501, according to the hip joint dynamic data, the thrust F2 of the hip joint against water in the up-down direction at different times is calculated;

[0028] S502, according to the hip joint dynamic data, the total moving distance S2 of the hip joint in the up-down direction at different times is calculated;

[0029] S503, the work operation is performed according to the thrust F2 and the total moving distance S2 at different times to obtain the hip joint dynamic power data.

[0030] Further, in step S6, the n-dimensional space Euclidean distance formula is used, as follows:

[0031]

[0032] Wherein, d(x, y) is the Euclidean distance between points (x1, x2,..., x n ) and (y1, y2,..., y n ) in the discrete data set of the actual swimming posture data and the standard swimming posture data.

[0033] The beneficial effect of the present application is that when the athlete swims, the swimming posture correction data can be obtained by comparing the dynamic data of the hip joint and the dynamic data of the limbs, mainly the legs, and the swimming posture correction data is suitable for the physical data of the athlete, so that the coach and the athlete can fully correct the swimming posture according to the swimming posture correction data, thereby increasing the swimming efficiency and further improving the performance in competitive games. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A step flowchart of the method of the present application;

[0035] Figure 2 A step flowchart in step S3 of the present application;

[0036] Figure 3 A schematic diagram of the three-dimensional swimming posture action data of the athlete in visual 3D in the present application;

[0037] Figure 4 A schematic diagram of the three-dimensional swimming posture action data of the lower body of the athlete in visual 3D in the present application; DETAILED DESCRIPTION

[0038] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0039] The following examples are tested by a swimmer of the school, and the swimmer adopts breaststroke and freestyle swimming posture to test 50 meters, respectively, wherein the completion time of 50 meters of breaststroke is 38.34 seconds, and the completion time of 50 meters of freestyle is 29.75 seconds. It should be noted that the athlete will jump into the water from the stepping plate at the starting point, and slide a distance in the water by swinging the legs, the purpose is to fully utilize the inertial force of jumping into the water, and in this stage, the swimming posture is not adopted, only after the sliding is completed, the corresponding swimming posture is adopted to provide further power for subsequent advancement. Since the swimming posture is not adopted in this stage, only the hip dynamic data can be calculated. The present embodiment provides a method for adjusting the swimming posture according to the hip joint dynamics:

[0040] A multi-frequency bioelectrical impedance measurement instrument is used to measure the height, weight, skeletal muscle rate, body fat mass, body surface area and waist-hip ratio of the target athlete to obtain the physical data of the target athlete. The multi-frequency bioelectrical impedance measurement instrument can accurately measure the physical data of the human body, minimizing errors. In the present embodiment, the height is 186.25 cm, the weight is 74.21 kg, the skeletal muscle rate is 42.6%, the body fat mass is 9.5%, the waist-hip ratio is 0.86, the upper limb surface area is 0.36 m 2, the lower limb surface area is 0.89m 2 , the hip surface area is 0.48m 2 .

[0041] The waterproof level sports sensor is attached to the target athlete, the waterproof level sports sensor is an electromyographic sensor and an inertial measurement unit with an ipx7 waterproof level, the number of waterproof level sports sensors on the hip is H, and the number of waterproof level sports sensors on the limbs is L, H≥2L; in this embodiment, the waterproof level sports sensors on the hip can be attached to the outside of the swimsuit or swim trunks, respectively on the front hip and the back hip, and evenly attached along the vertical direction, the total number is 12; the number of waterproof level sports sensors on the limbs is 5, among which the waterproof level sports sensors on the arms are attached in turn on the back of the hand, the forearm, the upper side of the elbow, the upper arm, and the deltoid muscle; the waterproof level sports sensors on the legs are attached in turn on the instep, the shank, the upper side of the knee, the thigh, and the crotch on the inner side of the thigh; each waterproof level sports sensor is used to obtain three-dimensional swimming posture data of the target athlete, and each waterproof level sports sensor is in communication connection with the computer system of the terminal, the computer system is provided with analysis software for three-dimensional motion capture data such as visual 3D, and the three-dimensional swimming posture data is presented in visual 3D.

[0042] Underwater cameras and above-water cameras are arranged in the swimming lane, in this embodiment, the swimming lane is a single swimming lane, and both sides of the single swimming lane are walls, the purpose is to prevent too many water ripples, water waves or water bubbles from affecting imaging; the above-water cameras are arranged on both sides of the single swimming lane and are evenly distributed along the length direction of the single swimming lane, those skilled in the art can freely adjust the number of above-water cameras according to the length of the swimming lane, in this embodiment, the length of the swimming lane is 50 meters, and the number of above-water cameras is 5, which are evenly arranged every 10 meters along the length of the swimming lane, in order to prevent water splashes from affecting shooting, the above-water cameras are arranged at a certain distance from the water surface and are raised, which can ensure good angle shooting of the athlete's swimming posture and prevent water splashes from splashing onto the lens. The underwater cameras are arranged underwater and distributed on both sides, the bottom wall and the starting and ending point side wall of the swimming lane where the target athlete is located. In order to make the underwater cameras have clear imaging, the underwater cameras need to be calibrated to obtain the parameters of the underwater cameras.

[0043] The underwater camera is calibrated to obtain the parameters of the underwater camera, and the specific steps include: cutting the underwater swimming posture high-speed image into swimming posture images at different time points; presetting a Zhang Zhengyou chessboard calibration plate with 7*10 black and white grids and an origin of a world coordinate system, detecting feature points in the swimming posture image to obtain pixel coordinate values and physical coordinate values of each corner point on the Zhang Zhengyou chessboard calibration plate; solving the internal parameter matrix and the external parameter matrix of the underwater camera according to the relationship between the pixel coordinate values and the physical coordinate values of the corner points of the Zhang Zhengyou chessboard calibration plate; calculating the radial distortion coefficient of the underwater camera; and calculating the internal parameters and the external parameters by using the Zhang Zhengyou calibration method and through the opencv library to obtain a group of chessboard calibration plate photos.

[0044] The internal parameter matrix is:

[0045]

[0046] wherein F represents a focal length; fx represents the length of the focal length in the x-axis direction; fy represents the length of the focal length in the y-axis direction; u0 and v0 represent principal point coordinates; γ represents a coordinate axis tilt parameter; the internal parameter matrix is an attribute of the underwater camera itself, and the parameters can be obtained through calibration;

[0047] The external parameter matrix is: R is the product of the rotation matrix of each axis, wherein the rotation parameter of each axis is T is a translation parameter (Tx, Ty, Tz).

[0048] The internal parameter matrix and the external parameter matrix are obtained, the camera distortion coefficient is calculated through the Zhang Zhengyou calibration method, a transformation opposite to the distortion is performed, the distortion is eliminated, and the monocular camera parameters are obtained.

[0049] The internal parameter matrix is:

[0050]

[0051] The tangential distortion (p1, p2) is [0 0], wherein the monocular camera parameters include the internal parameter matrix, the radial distortion parameters k1 and k2, and the tangential distortion parameters p1 and p2; the radial distortion coefficient is determined by using the first two items of the Taylor series expansion around the principal point, and the mathematical expression is:

[0052]

[0053] (u, v) represents ideal pixel coordinates without distortion, (u', v') represents pixel coordinates in the actual radial distortion case, (u0, v0) represents the principal point, (x, y) represents continuous image pixel coordinates in the ideal case without distortion, and (x', y') represents continuous image pixel coordinates in the actual radial distortion case; k1 and k2 represent the first two order distortion parameters; and the formula is converted into a matrix form:

[0054]

[0055] Calculate (x, y) by camera model; get (u0, v0) by the solved intrinsic matrix; solve (u, v) from the world coordinate point of the object in the camera model; calibrate n images containing chessboard, each image has m corner points of the chessboard, get 2mn equations, optimize the result by least square method, get the radial distortion parameter k = [k1, k2] by the equation k = ((D T D) -1 D T )d, where D is the coefficient matrix of the equation on the left side, d is the matrix composed of the difference between the distorted pixel coordinates and the non-distorted pixel coordinates on the right side of the equation; perform maximum likelihood estimation on the solved distortion parameter and the intrinsic and extrinsic parameters under the ideal non-distortion condition; increase k1, k2 in the parameter estimation to minimize the following function: maximum likelihood estimation: calibrate n images containing chessboard, each image has m corner points of the chessboard, let the corner point M j The projection point on the image under the calculated camera matrix is

[0056]

[0057] where R i and t i are the rotation matrix and translation vector corresponding to the ith image pair, and K is the intrinsic matrix; the probability density function of the corner point M ij is:

[0058]

[0059] Construct the likelihood function:

[0060]

[0061] Make L reach the maximum value, and the following equation is minimized:

[0062]

[0063] Optimize the intrinsic matrix, extrinsic matrix and radial distortion coefficient by Levenberg-Marquardt method. Levenberg-Marquardt method can provide a numerical solution for nonlinear minimization. This algorithm can achieve the advantages of combining Gauss-Newton algorithm and gradient descent method by modifying parameters during execution, and improve the shortcomings of the two methods.

[0064] The displacement data, the four-limb dynamic data and the hip joint dynamic data of the target athlete are obtained according to the three-dimensional swimming posture motion data and the high-speed image of the swimming posture; the speed data, the four-limb dynamic power data and the hip joint dynamic power data of the target athlete are calculated, and the actual swimming posture data is obtained by combining the physical sign data.

[0065] The specific steps for calculating the four-limb dynamic power data are as follows: the thrust of the four limbs against water F1 at different time instants is calculated according to the four-limb dynamic data; the total moving distance of the four limbs in water S1 at different time instants is calculated according to the four-limb dynamic data; and the four-limb dynamic power data is obtained by performing work operation according to F1 at different time instants. In this embodiment, the upper limb motion in breaststroke is taken as an example, and the upper limb motion of the athlete in breaststroke needs to be disassembled, and the following actions are repeatedly performed: the hands are stretched forward with palms together, the hands are opened to the sides and pressed downward, and the hands are brought back to the chest with palms together. The moving distance of the left arm and the right arm is obtained by adding the total moving distances according to the above three steps to obtain the total moving distance of the forelimbs. The lower limbs are disassembled in the same way, and details are not repeated. The resistance formula is C represents the resistance coefficient, p represents the water density, A represents the contact area, and V is the relative motion speed of the athlete and the liquid. For example, from the 0th second to the 1st second after changing to the breaststroke posture, the total moving distance of the forelimbs is 3.12 m, which can be measured according to the disassembly of the above steps and the sensing of the waterproof level motion sensor. The relative motion speed v of the forelimbs against water in this time period is 2.3 m / s. In order to simplify the model, the water resistance coefficient can be kept unchanged. It is assumed that when the hands are stretched forward with palms together, the contact surface between the arms and water is the back side of the arms, the area is 0.18 m 2 , when the hands are opened to the sides, the contact surface is the back side of the arms, the area is 0.18 m 2 , when the hands are pressed downward, the contact surface is the inner side of the arms, the area is 0.18 m 2 , and when the hands are brought back to the chest, the contact surface is the inner side of the arms, the area is 0.18 m 2 . Therefore, when the water density p is known, the resistance of water to the arms at different time instants can be calculated, and the work of the arms in this time period can be obtained according to the work formula W=FS, where F is the resistance and S is the distance.

[0066] Similarly, the upper limb motion of the athlete in freestyle needs to be disassembled. Due to the particularity of freestyle, the arm will be out of the water surface at a certain stage, so the arm out of the water surface is ignored, and only the arm in the water is calculated. The following actions are repeatedly performed: turning the body, lifting one arm out of the water, putting the arm into the water and pressing water to the waist, turning the body, lifting the other arm out of the water, putting the other arm into the water and pressing water to the waist. The moving distance of the left arm and the right arm is obtained by adding the total moving distances according to the above steps to obtain the total moving distance of the forelimbs. The lower limbs are disassembled in the same way, and details are not repeated. The resistance formula is C represents the drag coefficient, ρ represents the water density, A represents the contact area, and V is the relative velocity of the athlete's arm to the liquid. For example, during the transition from second 0 to second 1 when switching to freestyle, based on the above steps and the sensing by the waterproof motion sensor, the total distance the athlete's left and right arms move in the water can be measured to be 3.28m. The relative velocity v during this time period is 1.68m / s. To simplify the model, the water drag coefficient can be left unset. When a single arm enters the water and presses it towards the waist, the contact surface between the arm and the water is the front side of the arm, with an area of ​​0.18m². 2 Given the water density ρ, we can calculate the resistance of the water to the arms at different times. Based on the work formula W=FS, we can calculate the work done by the arms during that time period, where F is the resistance and S is the distance.

[0067] The specific steps for calculating hip joint dynamic power data are as follows: Based on the hip joint dynamic data, calculate the thrust F2 of the hip joint in the vertical direction against the water at different times; based on the hip joint dynamic data, calculate the total vertical movement distance S2 of the hip joint at different times; perform work calculations based on F2 and S2 at different times to obtain the hip joint dynamic power data. Since the hip joint amplitude is relatively large in freestyle swimming, this embodiment takes freestyle as an example and needs to break down the athlete's hip movements during freestyle swimming. Due to the special nature of freestyle swimming, the hip will repeatedly and alternately swing up and down; only the vertical swing distance of the hip at different times needs to be calculated. The resistance formula is... C represents the drag coefficient, ρ represents the water density, A represents the contact area, and V is the relative velocity between the athlete's hip and the liquid. For example, from second 0 to second 1, the athlete's hip, according to the waterproof motion sensor, can be measured to have a vertical swing distance of 36.42 cm, and a relative velocity v of 18.21 cm / s during this time period. To simplify the model, the water drag coefficient can be left unset. Assuming the hip moves downwards, the contact surface of the hip is the front, with an area of ​​0.24 m². 2 When the hip moves upward, the contact surface of the hip is the back, with an area of ​​0.24m². 2 Given the water density ρ, the resistance of the water to the hip can be calculated at different times. According to the work formula W=FS, the work done by the arms during that time period can be calculated, where F is the resistance and S is the distance.

[0068] Preset standard swimming stroke data is generated by the coaching team or athletes based on measured physical characteristics and their expectations for training or competition data. In this embodiment, the preset speed is 25 seconds to complete 50 meters freestyle; the preset hip joint dynamic data is 15.52 cm for the vertical fluctuation range of the hip in 50 meters freestyle, etc. Those skilled in the art can reasonably set these data according to the physical characteristics and expectations of different swimmers. The aim is to ensure that the athlete's training data closely approximates the expected standard swimming stroke data. Both actual and standard swimming stroke data consist of a series of discrete points. The Euclidean distance between each discrete point in the actual swimming stroke data and each discrete point in the standard swimming stroke data is calculated. Due to the large number of data dimensions, an n-dimensional Euclidean distance formula is used, as follows:

[0069]

[0070] Where d(x,y) is a dataset of actual swimming stroke data and standard swimming stroke data, with points (x1,x2,...,x...) as the coordinates. n ) and (y1,y2...,y n The difference value is obtained by measuring the Euclidean distance between the two points. Based on the difference value, swimming posture correction data is obtained. The swimming posture correction data can be used by athletes and coaching teams to see if their hip joints or limbs meet the preset standards. Targeted training can be carried out in the next training session. If the vertical swing of the hip joint exceeds the preset value, it is necessary to test again in the water after special training on the vertical swing of the hip joint, so as to continuously improve.

[0071] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A method for dynamically adjusting swimming posture based on the hip joint, characterized in that, Includes the following steps: S1. Analyze the physical characteristics of the target athlete to obtain the physical characteristic data of the target athlete; S2. Attach waterproof motion sensors to the target athlete. The number of waterproof motion sensors located on the hip is H, and the number of waterproof motion sensors located on the limbs is L, where H ≥ 2L. The waterproof motion sensors are used to obtain three-dimensional swimming posture data of the target athlete. S3. Simultaneously acquire high-speed images of the target athlete's swimming postures on and under the water using an underwater camera and a surface camera, and perform calibration operations on the underwater camera to obtain the parameters of the underwater camera. S4. Obtain the displacement data, limb dynamic data, and hip joint dynamic data of the target athlete based on the three-dimensional swimming motion data and high-speed swimming images; S5. Calculate the target athlete's speed data, limb dynamic power data, and hip joint dynamic power data based on the three-dimensional swimming motion data and high-speed swimming image, and combine the vital signs data to obtain the actual swimming motion data; S6. Preset standard swimming stroke data, calculate the Euclidean distance between each discrete point data in the actual swimming stroke data and each discrete point data in the standard swimming stroke data, and obtain the difference value; S7. Obtain swimming posture correction data based on the difference values; Step S3, calibrating the underwater camera to obtain its parameters, specifically includes the following steps: S31. The underwater high-speed swimming posture image is segmented into swimming posture images at different times; S32. Preset a fixed-size Zhang Zhengyou checkerboard calibration board and the origin of the world coordinate system, detect feature points in the swimming stroke image, and obtain the pixel coordinate value and physical coordinate value of each corner point on the Zhang Zhengyou checkerboard calibration board based on the feature points. S33. Solve for the intrinsic parameter matrix and extrinsic parameter matrix of the underwater camera based on the relationship between the pixel coordinate values ​​and the physical coordinate values; S34. Calculate the radial distortion coefficient of the underwater camera; S35. Optimize the intrinsic parameter matrix, extrinsic parameter matrix, and radial distortion coefficient using the Levenberg-Marquardt method; In step S5, the specific steps for calculating the dynamic power data of the limbs are as follows: S51. Based on the dynamic data of the limbs, calculate the thrust F1 of the limbs on the water at different times; S52. Based on the dynamic data of the limbs, calculate the total distance S1 of movement of the limbs in the water at different times; S53. Perform work calculations based on the thrust F1 and total moving distance S1 at different times to obtain dynamic power data of the limbs; In step S5, the specific steps for calculating the dynamic power data of the hip joint are as follows: S501. Based on the dynamic data of the hip joint, calculate the thrust F2 of the hip joint on the water in the vertical direction at different times. S502. Based on the hip joint dynamic data, calculate the total vertical movement distance S2 of the hip joint at different times. S503. Perform work calculations based on the thrust F2 at different times and the total moving distance S2 to obtain dynamic power data of the hip joint.

2. The method for dynamically adjusting swimming posture based on the hip joint according to claim 1, characterized in that, In step S1, the vital signs data of the target athlete are obtained by multi-frequency bioelectrical impedance measurement.

3. The method for dynamically adjusting swimming posture based on the hip joint according to claim 2, characterized in that, In step S2, the waterproof motion sensor includes an electromyography sensor with a waterproof rating of IPx7 and an inertial measurement unit.

4. The method for dynamically adjusting swimming posture based on the hip joint according to claim 3, characterized in that, In step S3, the underwater cameras are distributed on the left and right sides of the swimming lane where the target athlete is located, the bottom wall, and the side wall of the start and finish line.

5. The method for dynamically adjusting swimming posture based on the hip joint according to claim 1, characterized in that, In step S6, the Euclidean distance formula in n-dimensional space is used, as follows: ； in, This represents the discrete data center of the actual swimming stroke data and the standard swimming stroke data. and The Euclidean distance between them.

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