RESEARCH ON THE APPLICATION OF SPORTS BIOMECHANICS IN IMPROVING ATHLETES’ PHYSICAL FITNESS IN TRACK AND FIELD PHYSICAL EDUCATION COURSES

1. Introduction

The public favors basketball because of its good fitness effect and viewing effect. After more than 100 years of development, its competitive level and level have been continuously improved. Prolonged physical activity can easily lead to muscle fatigue in athletes. Basketball is a multi-limb competitive sport. Its steals, emergency stops, jump shots, dunks, blocks, and other actions are all completed by the upper body, and the contraction and relaxation of the upper body muscles drive the movement of the arm. And in the movement that directly touches the ball with the hand, the dependence on the upper body is the greatest.¹ This paper uses the method of sports biology to test the physical fitness of eight male basketball players. The content of the physical examination is the isokinetic muscle strength of the shoulder joint. This paper aims to investigate the effect of shoulder isokinetic muscle strength on athletic performance. The results of this paper can provide a scientific basis for the daily training of Chinese men’s basketball players. The results of this study can effectively prevent the occurrence of shoulder exercise fatigue.

2. General Information and Methods

2.1. Subjects

This study selected eight active men’s basketball players who had undergone 2–3 years of vocational and technical training. Athletes ranged in age from 16 to 18 years (Table 1).

2.2. Investigation method

Different angular velocities (60°/s, 180°/s, and 240°/s) are present in this paper. A rapid clinometry system such as the BiodexS4 is used.² This paper processes and analyzes it by computer and prints out the test results. Eight patients underwent shoulder joint testing in an anatomical sitting position. Athletes should do a moderate 5-min warm-up exercise to ensure shoulder stability before the test begins. This avoids accidents. Athletes performed different speed test times: exercise to 60°/s with a 1-min interval, 60°/s to 180°/s with a 3-min interval, and 180°/s to 240°/s with a 3-min interval. The entire content of this experiment strictly complied with the regulations of the isokinetic muscle tester.

2.3. Simulation and simulation of biomechanical systems

The internal environment of organisms has a certain complexity. In this paper, to better obtain biomechanical signals, it is necessary to analyze the effect of physiological stimuli on the body with the help of external force devices. Typically, these devices include cell culture and control systems. The primary forms of biomechanics are fluid shear, compressive and tensile stress, and shock waves. Since the sheer force of the fluid is the main effect of the adaptability of the bone to the mechanical environment, many scholars have used it to analyze the conduction mechanism of the bone. Currently, in vitro analysis of fluid shear forces mainly employs two devices: vertebral flow and parallel-plate flow. In addition to the pressure created by the liquid, it can also be created by a flat plate. Such devices are often used to simulate the stress conditions of human cartilage.³ Tensile stress can be divided into uniaxial and biaxial. In both force-enhancing devices, the cells are on a special elastic membrane. Cells exert different tensions on them with different forces. A uniaxial stretching device with good performance will also generate a stress perpendicular to the pressure on its surface during the resulting stretching process. This force can accurately reflect the force state of the body’s internal structure. This paper uses various biological forces collected by the instruments mentioned above. This can ensure the integrity and effectiveness of the plane’s multi-mode low-frequency biomechanical signal processing.

2.3.1. Preset signal

Signal preprocessing mainly includes signal acquisition, filtering, spectrum analysis, displacement amplitude transformation, etc. In acquiring the signal, the photoelectric encoder is used in this paper. Its minimal analytical expression is :

where $m_{\partial }$ is a group of pulses generated each time the encoder is rotated. In this signal acquisition system, 2000 pulse signals are obtained by turning 1 circle. Its minimum resolution is 0.18. When the body is active, the nervous system stimulates the neurons with electric current to put them in a state of excitement. This can create muscle tension and tension. On this basis, the biomechanical signal with muscle signal as input is established in this paper.⁴ This paper takes the joint angle as the output of the biomechanical model. This paper uses a ninth-order Butterworth low-pass filter to filter the signal to remove high-frequency interference. Since an acceleration sensor is used, the amplitude obtained after spectrum analysis must be converted into displacement. In this paper, the displacement time value of sinusoidal vibration is obtained by the following method : In this paper, when derivation on both sides of Eq. (2), the following velocity expression can be obtained : Then, Eq. (3) is solved to obtain the calculation formula of acceleration In this way, when the sinusoidal vibration displacement peak is ${\kappa }_{\sigma }$, its relative acceleration peak is ${\kappa }_{\sigma }{\sigma }^2$, and there is the following relationship between the two where ${\lambda }_{\sigma }$ is represented in the equation by the acceleration peak of the vibration and $R$ is the frequency of the vibration.

2.3.2. The application of wavelet analysis in image fusion

The preprocessing based on biomechanical signal adopts the wavelet analysis method to realize the fusion of muscle images.⁵ The wavelet transform is a local transformation of space and frequency. It can effectively extract the information in the image and realize the division of the low-frequency band. The image fusion process based on wavelet analysis mainly includes wavelet analysis on the target muscle. In this way, low-frequency and high-frequency sub-images can be obtained. According to the characteristics of wavelet decomposition coefficients, different fusion algorithms are used to process the fusion operators of frequency components with different resolutions. The wavelet transform $P(x)$ can be regarded as the decomposition and reconstruction of the wavelet function $\eta (x)$ and the scale function $\lambda (x)$. The decomposition formula of the wavelet of the signal $P(x)$ at a particular scale $T$ is as follows :

where $C(i,j)$ and $D(i,j)$ represent the scale coefficients and wavelet coefficients of the scale $T$, respectively. The fusion method and rules of muscle images significantly influence the speed and effect of fusion. To improve the processing efficiency of the signal, this paper must distinguish between high frequency and low frequency.⁶ Therefore, in high-frequency fusion, the consistency check rule of adjacent windows is introduced into discrete wavelet analysis to ensure the continuity and stability of fusion. The change of a specific area in the muscle image can reflect the grayscale distribution of each pixel in the area. This can reveal the details and texture information of the image. Therefore, we must choose a local region fusion suitable for low-frequency wavelet coefficients when performing fusion.

(1)	In the object image, the number of points $(a,b)$ is regarded as the local variances $V_i^j(a,b)$ and $V_k^j(a,b)$. $$V_m(a,b)=\sum _{i=1}^m{\omega }_i(a^{\prime },b^{\prime })[P(x)(a+a^{\prime },b+b^{\prime })].$$(7)
(2)	Perform local region correlation matching $N_{OP}$ on the image. $$N_{OP}(a,b)=\sum _{i=1}^m[{\omega }_i(a^{\prime },b^{\prime })].$$(8)
(3)	This paper combines local matching and variance.7 This paper obtains a suitable threshold by calculating the fusion weight in the wavelet space. $$D_l(a,b)=\left\{\begin{array}{c}{D}_s(a,b)V_s(a,b)\ge V_d(a,b),\hfill \\ D_d(a,b)V_s(a,b)<V_d(a,b).\hfill \end{array}\right.$$(9)

This paper uses the fusion coefficients obtained by the above methods for fusion.

2.4. Statistics

The results of the experiments were organized and analyzed through Excel spreadsheets.

3. Results and Analysis

3.1. 60°/s, 180°/s, and 240°/s shoulder torque peak test

The peak torque is the golden indicator for measuring isokinetic muscle strength in humans. It can well reflect the maximum muscle strength of athletes during isokinetic exercise.⁸ The average flexor moments of the left shoulder at 60°/s, 180°/s, and 240°/s were averaged as 26.29, 21.45, and 9.9, respectively. The results showed that the average peak extensor torque was 43.12, 44.66, and 27.72.

The mean peak flexor torque at the right shoulder joint was 23.65 and 45.76, respectively, at 60°/s. The mean peak flexor torque and extensor force at 180°/s were 16.06 and 42.79, respectively.⁹ The mean peak flexor and extensor torque at 240°/s were 6.71 and 30.25, respectively. The torque peak decreases with an increasing angular velocity and has an inverse relationship (see Fig. 1) (as shown in Table 2).

3.2. Cyclic test results of 60°/s, 180°/s, and 240°/s to maximum power output

The purpose of the maximum work cycle test is to understand better the total output of the muscles under the limited state. In this way, we can better understand the ability of the tested muscles to generate, reproduce, and stabilize their functions.¹⁰ It can be seen from Table 3 that the maximum function of the left shoulder joint reached 48.07 in the movement of 60°/s, and the maximum function of the extensor muscle reached 88.33. At 180°/s, the maximum work cycle for the flexors is 48.07, and the extensors is 80.85. The maximal function of the flexors reached 11.77, and the maximal function of the extensors reached 43.67 during a movement of 240°/s.

The maximum work value of the right shoulder flexor at 60°/s was 42.9, and the extensor was 93.61. At 180°/s, the maximum work of the flexor was 16.72, and the extensor was 83.6. The maximum work value of the flexors during the 240°/s movement is 6.27, and the extensors is 49.17. The maximum princess period value decreases with the increasing angular velocity and is inversely proportional (Fig. 2).

3.3. Determination of shoulder fatigue index at 60°/s, 180°/s, and 240°/s

The formula for calculating the fatigue index when exercising at high-speed = (the work done by the muscle in the first three times − the work done in the following three times)/the work done in the third time × 100%. This value is related to the endurance of the muscles. The smaller the value, the stronger the muscular endurance of the athlete.¹¹ It can be seen from Table 4 that the fatigue index of the left shoulder joint is 57.53% and 31.9%, respectively, when performing 60°/s. In the case of 180°/s, the fatigue index of bending is 6.05% and 1.98%, respectively. The fatigue index of the unilateral shoulder performed at 240°/s was 63.91% and 9.02%, respectively.

As shown in Table 4, when the right shoulder was flexed within 60°/s, the fatigue indices were 20.79% and 17.16%, respectively. In the case of 180°/s, the fatigue index of bending is 20.35% and $-$144.1%, respectively. The fatigue index of the unilateral shoulder at 240°/s was 38.06% and $-$1.32%, respectively.¹² The most exhausted is 180°/s. Bending your shoulders is more prone to fatigue than stretching your shoulders (see Fig. 3).

4. Discussion

The movement of the human body depends on the skeletal muscles. More than 600 muscles make up different muscle groups. These muscle groups can complete various movements of the human body. The strength of these muscles will affect the training effect of the athletes and have a particular impact on their performance. Existing studies have shown that athletes’ muscle strength shows significant sports characteristics. The most basic in evaluating athletes’ unique sports ability is the evaluation of muscle strength.¹³ The shoulder is the central movement joint of basketball players, and it plays a pivotal role in shoulder extension.

The peak torque is the “golden data” for measuring the human body’s isokinetic muscle strength. Which can accurately reflect the maximum muscle strength of the body when the athlete is performing the isokinetic exercise. The shoulder is the most critical part of the upper body muscles. When performing isokinetic movements, the peak torque in the shoulder can reflect the maximum power output of the athlete’s muscles.¹⁴ The torque peaks on the left shoulder are smaller than on the right, which is the best. The maximum torque of the shoulder flexors is less than that of the extensors. As the angular velocity increases, the torque peak has a negative correlation.

The literature pointed out that an excessive flexion–extension ratio of the shoulder can lead to the balance of the agonist and antagonist muscles during activities, and long-term imbalance can also lead to joint damage. Prime movers and antagonists are two different muscles whose actions are mutually exclusive, whereas human muscles follow the opposite rules.¹⁵ In physical activity, prime mover and the antagonist’s muscles interact and alternate.

The cycle that measures the maximum shoulder work value measures the total muscle output of the participant under maximum load that reflects the muscle’s ability to generate, regenerate, and reliability throughout the movement (the lower the value, the more repeatability). The period of maximum work value refers to the total muscle output of a male basketball player at full speed. The results show that when the angular velocity increases, the maximum work value cycle intensity of the shoulder is positively correlated with the angular velocity, indicating that the strength and recovery ability of the shoulder muscles are better.¹⁶ The shoulder extensors have more cycles than the flexors, suggesting that the flexors are more important for the cycle of isokinetic movement. The maximum work of the left shoulder joint was less different from that of the right, suggesting that the muscle strength of the left and fitting shoulder joints was similar.

The fatigue index in the isokinetic exercise is the work fatigue degree of the muscle, and its calculation formula = [(the work done by the muscle for the first three times − the work done in the last three times)/the work done in the third time] × 100%. In isokinetic exercise, the fatigue index reflects the endurance of the muscles. At 180°/s, the fatigue index of the shoulder is the lowest, and the muscle strength of the shoulder joint is the best. The fatigue index of the shoulder flexors is higher than that of the extensors, indicating that the extensors have better endurance.¹⁷ The results showed that the exercise intensity of the left shoulder was better than that of the right shoulder. The results showed that male basketball players’ index of shoulder extensors was higher than that of flexors. With the increase in the angular velocity, the peak flexor and extensor strength also decreased. Under the conditions of 60°/s and 240°/s angular velocity, the shoulders of the male basketball team are more prone to fatigue. They are more likely to cause the subjects to produce lower maximum work capacity and lower reliability than shoulder extension.

At the same time, the frequency of exercise is also closely related to the coordination of the prime mover and antagonist’s muscles. Therefore, the prime mover and antagonist’s muscles are only partial movements, not a whole. However, many people focus on the prime mover muscles in strength training and ignore the antagonist’s muscles. It is easy to regard some muscles as the prime mover muscles of the movement and regard them as part of determining the result of the exercise. In addition, the main factor that produces sports injuries during exercise is the imbalance between the prime mover and the antagonist’s muscles.

5. Conclusion

For the men’s basketball team, strengthen physical training. For male basketball players, the training of isokinetic muscle strength is 60°/s. It can increase isokinetic muscle strength in regular training. Men’s basketball teams should focus on isokinetic muscle strength exercises at 180°/s. In particular, the muscles on the left side need to be exercised to achieve a balanced development of the movement frequency.