Effects of Resuming Training Using Yoga on Physical Functions and Fitness of Taekwondo Athletes After High-intensity Training

Objective: This study aimed to analyze the effects of resuming training using yoga on the physical functions and tness of Taekwondo athletes after high-intensity training. Method: A total of 50 Taekwondo athletes from this college were randomly divided into 2 groups. 25 athletes are in the control group, and they massage their muscles after high-intensity training to help recovery. Meanwhile, 25 athletes are in observation groups, and they practice yoga after high-intensity training for resuming training. After 8 weeks, the physical functions and tness of the two groups of athletes were compared. Result: There was no statistically signicant difference between the observation group and the control group before starting high-intensity training from 1st week to 8th week (P<0.05). From the 4th week to the 8th week after high-intensity training, the observation group's heart rate, heart rate after resuming training and subjective physical sensation degree scores were lower than the control group (P<0.05). After 8 weeks of resuming training in the observation group, hemoglobin was higher than the control group, blood urea nitrogen and creatine kinase was lower than the control group (P<0.05). The observation group's exion test results of the sitting position after 4th week and 8th week of resuming training were higher than those of the control group (P<0.05). Conclusion: The use of yoga for resuming training after high-intensity training can improve the physical function and tness of Taekwondo athletes, improve the exibility of athletes and promote their professional skills.


Background
Professional Taekwondo athletes have a high level of competition, and contests between athletes must ensure good physical reserve, so as to ensure that their skills are fully displayed on the competition eld. Athletes' physical reserve must go through the process of exercise stimulation, fatigue, recovery, and adaptation, and the athlete's physical tness can be recovered excessively after the process is completed.
Athletes generate fatigue after exercise stimulation. In this case, if the fatigue is not eliminated in time, athletes will not be able to adapt to further training load, which will eventually have an adverse effect on the training results [1][2].
Taekwondo training has a large amount of exercise, high intensity, and needs to be repeated continuously. It belongs to a type of periodic exercise. If the resuming training is not done after each training, fatigue is easy to accumulate, and the body will not adapt to the training for a long time. Athletes will not be able to complete the prescribed training content, which will affect the athlete's athletic ability [3]. For the recovery of high-intensity training, athletes generally choose some moderate and light-load training to achieve the relief of exercise fatigue. Alternating the large load of training with the moderate and low load of recovery training can make different metabolites interact with each other, thereby promoting a better metabolism of a party [4]. In the past, the commonly used restorative methods mostly used jogging, stretching, and ice compress. However, the application effect of a single method is not outstanding, and it usually takes a long time to harvest the effect, and it is necessary to alternately perform different methods to recover [5].
Recently, Henan Taekwondo team has gradually tried yoga training after high-intensity training of Taekwondo to help recovery. Yoga, as a movement to regulate the state of mind and body, is mainly carried out by adjusting breathing and performing posture exercises. Many studies on the physiological and psychological effects of yoga on the body suggest positive conclusions [6]. There is not much research on whether yoga is effective as a small-intensity recovery training method after high-intensity training. This study speci cally analyzed 50 Taekwondo athletes of Henan Taekwondo team in training, and provided new directions for the selection of Taekwondo athletes' recovery training methods after training.

Materials
In 2019, the Henan Taekwondo team selected 50 male athletes in training as the subjects of this study.
They were divided into 2 groups by random drawing method, and there are 25 athletes in control group and observation group, separately. Before participating in this study, all athletes participated in the training normally, and their activities, life patterns, and emotional states were not abnormal. And all the athletes have received professional taekwondo training for more than 2 years, and have no health problems before participating in the study.

Methods
All athletes in the two groups receive training with the same exercise intensity and the same amount of exercise every day according to the training plan. The control group massaged their muscles after each training session to help relax for 20 minutes. The observation group received yoga rehabilitation training after each training session for 20 minutes.
Method of control group. The players are divided into groups of two. One of them is lying on a yoga mat, the other one is stepping on the muscles of the whole body including the legs, waist, back, and hands with his feet, and the two players exchange after a sense of relaxation.
Method of observation group. Yoga preparation: use 5 minutes to adjust your breathing yourself. Yoga practice: Choose forward bending sitting, one leg side stretching, swinging, big worship, supine twisting, crescent and horseback twisting, pulling feet, leg extension, pigeon style and neck extension for practice [7] for ten minutes. End of Yoga: Keep lying on your back for 5 minutes. You should pay attention to the following two points during yoga training. The rst is that the selected yoga action must be combined with the characteristics of Taekwondo. And it is necessary to focus on the stretching of the ankle, hip, shoulder, and waist for the speci c fatigued parts of the athlete after the training. The second is that during yoga training, all postures must not cause discomfort to the athletes. During the training, guide the athletes to breathe steadily and experience the feeling of body feedback.

Observation Index
Physical function: Determine the heart rate, subjective physical sensation, hemoglobin, blood urea nitrogen and creatine kinase levels of the two groups of athletes. The heart rate needs to be measured before training, immediately after high-intensity training, and after recovery. The degree of subjective physical sensation is completed using the simpli ed version of the subjective physical sensation table [8], which is divided into 10 levels. Level 0 means no feeling, level 1 and level 2 means weak, level 3 means mild, level 4 means slightly stronger, level 5 means strong, level 6 means medium, and level 7 means very strong, level 8, level 9 and level 10 means very strong. The scores are 0-10, respectively. The higher the score, the worse the physical strength. The levels of hemoglobin, blood urea nitrogen, and creatine kinase was measured after the test of 2ml of elbow vein blood collected by the team doctor under sterile conditions.
Physical tness: Considering that the exibility of Taekwondo athletes is very important, this study adopts exibility as an evaluation index of athletes' physical tness. Speci cally, measure the exion distance of the sitting position. Each athlete performs two sitting exion tests to record the nal result with better results.

Statistical Method
Statistical analysis was performed with SPSS23.0, and measurement data was expressed as (±s), and results were compared using independent sample t test. Counting data is represented by [n(%)], X2 test is used for comparison of results, ANVOA is used for multi-point comparison within the group, F test is used, graphs are made by Graphpad Prism 8. If P<0.05, the difference is considered statistically signi cant.

Physical Data
The average age, height, body weight, body mass index (BMI) and training time of the 25 athletes in the observation group and the 25 athletes in the control group were not signi cantly different, and there was no statistical signi cance (P> 0.05) ( Table 1). Heart Rate Before Training The heart rate level of the observation group before starting high-intensity training from 1st week to 8th week only uctuated about 1 time/min, and the heart rate comparison between different times showed no statistical difference (P>0.05). The heart rate of the control group uctuated only about 2 times/min before the beginning of high-intensity training from 1st week to 8th week. The comparison of heart rate between different times did not show statistical difference (P>0.05). There was no statistically signi cant difference between the observation group and the control group before starting high-intensity training from 1st week to 8th week (P<0.05) ( Table 2). There was no statistically signi cant difference in the instant heart rate between the observation group and the control group at 1st, 2nd, and 3rd week after high-intensity training (P>0.05). There was no statistically signi cant difference in the instant heart rate in the observation group from 1st week to 8th week after high-intensity training (P>0.05). There was no statistically signi cant difference in the instant heart rate in the control group from 1st week to 8th week after high-intensity training (P>0.05). The observation group's instant heart rate from 4th week to 8th week after high-intensity training was lower than that of the control group (P<0.05) (Figure 1).
Compared with the control group's instant heart rate after 1st week, 2nd week, and 3rd week after highintensity training, the observation group showed no signi cant difference (P>0.05). Compared with the instant heart rate after high-intensity training at 4th, 5th, 6th, 7th, and 8th week in the control group, the observation group was lower (P<0.05). * Indicates P<0.05 between the two groups.

Heart Rate After Resuming Training
There was no statistically signi cant difference in heart rate between the observation group and the control group after the resuming training at 1st, 2nd, and 3rd week (P>0.05). There was no statistically signi cant difference in the heart rate comparison of observation group from 1st week to 8th week after high-intensity training (P>0.05). There was no statistically signi cant difference in the heart rate comparison of control group from 1st week to 8th week after the recovery training (P>0.05). The heart rate of the observation group was lower than that of the control group from the 4th week until the end of the 8th week of resuming training (P<0.05) ( Figure 2).
Compared with the heart rate of the control group after 1st week, 2nd week, and 3rd week of resuming training, the observation group had no signi cant difference (P>0.05). Compared with the heart rate of the control group after 4th, 5th, 6th, 7th, and 8th week of resuming training, the observation group was lower (P<0.05). * Indicates P<0.05 between the two groups.

Subjective Physical Sensation
There was no statistically signi cant difference between the observation group and the control group in the scores of subjective physical sensation degree at 1st week, 2nd week, and 3rd week (P>0.05). There was a statistically signi cant difference in the subjective physical sensation degree scores in the observation group from 1st week to 8th week(P<0.05). There was no statistically signi cant difference in the scores of subjective physical sensation between the control group for adjacent 2 weeks. From the 4th week to the 8th week, the observation group's subjective physical sensation score was lower than that of the control group (P<0.05) (Figure 3).
Compared with the scores of subjective physical sensation after 1st week, 2nd week, and 3rd week of resuming training in the control group, the observation group showed no signi cant difference (P>0.05). Compared with the scores of subjective physical sensation after 4th, 5tth, 6th, 7th, and 8th week of resuming training in the control group, the observation group was lower (P<0.05). * Indicates P<0.05 between the two groups.

Biochemical Index
There was no signi cant difference in the levels of biochemical indexes hemoglobin, blood urea nitrogen, and creatine kinase before the resuming training between the observation group and the control group (P>0.05). After 8 weeks of resuming training, the observation group had a slight increase in hemoglobin, a slight decrease in blood urea nitrogen, and a slight decrease in creatine kinase. Meanwhile, in the control group, hemoglobin decreased slightly, blood urea nitrogen increased slightly, and creatine kinase increased slightly. However, there was no statistically signi cant difference between the two groups before and after resuming training(P>0.05). After 8 weeks of resuming training, the observation group had higher hemoglobin than the control group, blood urea nitrogen and creatine kinase was lower than the control group (P<0.05) (Figure 4).
Compared with the level of hemoglobin, blood urea nitrogen, and creatine kinase before the start of resuming training in the control group, there was no statistical difference in the observation group (P>0.05). Compared with the control group after 8 weeks of resuming training, the observation group had higher level of hemoglobin and lower level of blood urea nitrogen and creatine kinase (P<0.05). * Indicates P<0.05 between the two groups.

Physical Fitness
Before the start of resuming training, the sitting body exion test had no statistically signi cant difference between the observation group and the control group (P>0.05). After 4th week and 8th week of resuming training, the results of the sitting exion test of the two groups were gradually increased, and the difference between the groups at different times was statistically signi cant (P<0.05). After 4th week and 8th week of resuming training, the observation group exion test results were higher than the control group (P<0.05) ( Table 3).

Conclusion
The heart rate before training measures the heart rate of the athlete in the resting state before starting high-intensity training. The normal level is between 45-80 beats per minute. Generally, the lower the athlete's heart rate in the resting state, the stronger the heart function, the stronger the tolerance to training, and the better the body function. On the contrary, it reminds athletes that they lack the adaptability to the training load, which is easy to accumulate fatigue [9]. After high-intensity training, the instant heart rate is the exercise rate, and the highest heart rate of Taekwondo athletes under highintensity exercise is usually between 180-200 beats/min [10]. The level of the athlete's heart rate during exercise is related to the intensity of training. Under the same exercise load, the slower the athlete's heart rate rises, the better his physical function. The lower the maximum heart rate of an athlete who receives the same intensity training, the better the athlete's physical function [11]. The heart rate measured after the athlete completing their respective resuming training is heart rate after resuming training. Under the same exercise intensity, the faster the heart rate level decreases after resuming training, the better the cardiovascular function, the faster and better the body recovery speed [12]. This study showed that the observation group and the control group had no signi cant difference in heart rate levels from the rst week to the eighth week before starting high-intensity training. However, from the 4th week to the 8th week after high-intensity training, the instant heart rate and the heart rate after the resuming training in the observation group were both lower than the control group (P<0.05). This indicated that the athletes in the observation group slowed down their maximum heart rate during high-intensity exercise after receiving yoga for resuming training. Compared with the control group, the observation group has better physical function, and the heart rate recovers more quickly after receiving yoga for resuming training. It shows that the athletes in the observation group have stronger heart reserve capacity. After the highintensity training, the athlete's body function can be recovered more quickly, and the athlete can better adapt to the training load. As can be seen from the above results, yoga can play a regulating role in heart rate. Since yoga training itself places a high priority on breathing regulation, insisting on breathing regulation exercises helps improve the body's autonomic nerve function, and at the same time strengthens the conversion of excitement and suppression between sympathetic and parasympathetic nerves. In addition, it can coordinate the adjustment mechanism to keep the sports center always in a benign state of excitement, so that the heart rate can be reduced and the recovery of the athlete's heart rate after training can be accelerated [13][14].
The subjective physical sensation degree is simple and effective for evaluating exercise intensity. This evaluation is actually a combination of physiological function and psychological perception [15]. From the 4th week to the 8th week, the observation group's subjective physical sensation degree score was lower than the control group (P<0.05). It shows that the athletes in the observation group have better tolerance to the training intensity than the control group from the fourth week, indicating that the choice of yoga as a resuming training method can improve the athlete's physical strength. Because yoga practice emphasizes relaxation, slow movements can promote the recovery of body fatigue. In yoga practice, the self-perception ability can guide the body's relaxation, and continuous practice can let body learn to follow the body's wishes, which can speed up the relief of physical and mental fatigue [16]. In this study, many results of the observation group only began to show the difference from the control group at the fourth week. Since athletes have not contacted to yoga before, they are beginners. It is impossible to grasp the essence of yoga at the rst contact, so it is impossible to fully gather energy during practice, which may affect the function of yoga. With the extension of the practice time, the athlete's mastery is improved and the degree of integration with yoga is higher, so the role of yoga can be gradually highlighted.
Hemoglobin levels re ect exercise endurance, and high hemoglobin levels suggest that athletes have more physical strength and are less prone to fatigue during training [17]. Athletes' blood urea nitrogen level will increase early in a training cycle, and then slowly return to the normal range. This change suggests that there is enough stimulation of the exercise load, and the body can adapt well [18]. If the athlete's blood urea nitrogen continues to rise during training, there is no tendency to decrease at all, meaning that his body's function has not been restored completely. In this case, the rest of the athlete needs to be increased. Creatine kinase can re ect the slight damage caused by skeletal muscle. The uctuation of this index level is related to the amount and the intensity of training. Excessive exercise load stimulation will cause creatine kinase to increase, while at rest, creatine kinase will decrease [19]. The results of this study showed that after 8 weeks of resuming training, the observation group had higher hemoglobin than the control group, and blood urea nitrogen and creatine kinase was lower than the control group (P<0.05). This means that the athletes in the observation group have stronger exercise endurance, and their bodies can recover more quickly and completely after training. The study found that girls in sports and dance majors who received yoga resuming training after training had better recovery quality than natural recovery, and athletes had stronger ankle exor and extensor muscle groups after fatigue [20]. After training, football players choose yoga as resuming training. The results show that the players' relaxation experience and autonomous physiological response are better than the natural recovery group [21].
Taekwondo athletes with good exibility have higher movement amplitude and movement quality when participating in training and formal competitions, and the attack strength of the movements is stronger, and the athletes with better exibility are more likely to restore body function after exercise [22]. In this study, after 4 weeks and 8 weeks of resuming training, the sitting ante exion test results of the observation group were higher than those of the control group (P<0.05). It shows that the hip joint exibility level of the observation group receiving yoga resuming training is increased more. The higher the exibility of the hip joint of the athlete, the greater the action torque and the greater the completion of the action, and the more avoidance and attack can be completed in the same time. The function of yoga to improve exibility is as follows: Yoga posture movements include stretching, bending, pushing, twisting, and fully stretching the muscles of the body through various asanas. Continuous practice can effectively increase the stretchability of athletes' ligaments and exercise muscles, so it can promote the exibility of athletes [23][24]. Studies have suggested that the static stretch formed after exercise can speed up the recovery of skeletal muscle structure, strengthen the deformability of skeletal muscle, improve the exibility of the body, thereby helping to reduce the risk of sports injuries, and also help restore the function after training [25].
In summary, the use of yoga for resuming training after high-intensity training can improve the physical function and physical tness of Taekwondo athletes, enhance the exibility of athletes, and promote professional skills. However, this study included fewer subjects, and only selected male taekwondo athletes from the Henan Taekwondo team. In addition to the shorter research time, the results obtained may be somewhat biased, lacking su cient scienti city and representativeness. In the future, a longer period of time and a larger amount of studies should be carried out to further verify the value of yoga in the resuming training of athletes. Ethics approval and consent to participate This article has clearly informed the research subjects of the background, purpose, content, process, possible risks, powers and privacy protection of the research subjects in the research. And has obtained