UPPER LIMBS PHYSICAL FITNESS TRAINING IN VOLLEYBALL PLAYERS

ABSTRACT Introduction: Dedicated fitness training has greatly influenced many qualities required of volleyball players, but specific upper limb training is still poorly documented. Objective: Study the impacts of fitness training on upper limb strength and functional impacts during volleyball players’ ball throws. Methods: Twenty volleyball students were randomly divided into experimental and control groups for a six-week experiment. The experimental group mainly performed a training protocol involving ball throws while the control group continued with traditional training methods. The data regarding functional kinematics and fitness performance were collected and statistically compared. Results: In the experimental group, shoulder flexor strength evidenced an increase from 0.41±0.19 J/kg to 1.29±0.19 J/kg; elbow flexor strength elevated from 0.38±0.23 J/kg to 1.61±0.02 J/kg. On the specific functional performance, the peak score increased from 4.84±1.44 to 7.47±1.43; The overall score increased from 9.05±1.70 to 13.31±1.72. It was noted that the rate of increase of each index was more significant than that of the control group. Conclusion: Dedicated fitness training can improve the upper limb strength and hitting effect of volleyball players, and its combination with special strength training is recommended to improve the overall skills of athletes. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.


INTRODUCTION
The stability of hitting is one of the basic requirements in volleyball.Players need good physical ability and the ability to control the ball to achieve basic hitting success. 1 The higher the player's level is, the smaller the score gap is, the longer the game will be and the higher the physical requirements for the player will be. 2At this time, it is easy to hit the ball off the net or the ball flies out of the line.The slightest deviation in hitting will lead to more mistakes and higher loss rate. 3Therefore, players should not only learn different ways of hitting the ball, but also strengthen the hitting skills, including the height of the service point, the swing force of the hitting arm, the shape of the hand when hitting the ball, and the ability to control the opposite arm and body.Only in this way can we have a greater chance to send high-quality balls. 4The accuracy and coordination of hitting action depend on the integrity of technical action on the one hand, and the strength connection between muscles and the ability of nerves to accurately regulate muscles on the other hand. 5Its coordination has a great relationship with the stretching ability.If the muscle development is not balanced, it is very easy to have twisting throwing action and muscle damage.The upper limb strength of athletes is particularly important. 6Therefore, through the relevant research on volleyball training, this paper further summarizes the importance of batting training in improving volleyball players' upper limb strength and batting effect.

METHOD Experimental object
Through the methods of literature collection and actual interview, this experiment finally selected 20 sophomore volleyball students in a college of physical education through questionnaires.The study and all the participants were reviewed and approved by Ethics Committee of Chongqing Normal University (NO.CQNU-PT20N018).Twenty students were randomly divided into experimental group and control group.Through the comparison of basic information, it is determined that there is no significant difference between the physical fitness and other basic indicators of the two groups of students before the start of the experiment, and the volleyball training years are between 5-6 years, and there is no significant difference between the professional level of volleyball.There were no other relevant training courses except during the experiment to avoid the influence of irrelevant variables.The students were in good physical condition and had no injuries or other basic diseases recently, meeting the basic requirements of experimental training.Before the experiment officially started, the 20 students were explained, signed a letter of understanding on the basis of fully understanding the relevant training content and purpose of the experiment, and ensured that there were no unexcused absence, late arrival and early leave during the experiment that would affect the overall experimental training results.The batting training of the experimental group mainly includes the empty hand swing exercise at the core starting point, the upward throwing and spiking exercise for training spatial perception, the service exercise for training stability, and the cushion exercise for training arm control.The students are required to master the correct hitting movements as much as possible, understand the essentials of the movements and use them skillfully.

Design and implementation of experiment
In order to minimize the influence of independent variables during the experiment, the training ground and training time of the two groups were conducted in the volleyball court of the school gymnasium.After each class, the relevant indicators of the athletes should be measured.In addition, the living habits of the two groups of athletes remained relatively consistent.Ensure adequate sleep and rest time after training and class.

Experimental indicators
According to the purpose of the experiment, the main indicators of the test after the experiment include the relative total skill of the upper limb joints, the physical fitness of the players and the hitting effect.The test was conducted 24 hours after 6 weeks of training.
The relative total attack of upper limb joints was tested by the method of collecting EMG signals during exercise.The muscle groups of four parts, namely, shoulder flexor, shoulder extensor, elbow flexor and elbow extensor, were mainly selected for measurement.Before the test, athletes are required to prepare for about 20 minutes to avoid muscle strain during measurement.During the measurement, the EMG signal acquisition device should be fixed at a suitable position on the athlete's back for offline testing.Measure and record the data when selecting the spike swing action.Each indicator is recorded 3 times respectively, and the maximum value is taken.During the exercise, the interval between each measurement should be 1-2 minutes to avoid muscle fatigue.
The test of batting effect mainly includes four indicators, namely, spiking within the boundary, overhand service rate and expert skill score.It is used to measure the changes of players' hitting accuracy and volleyball skill level indicators after training.The measurement of athletes before and after the experiment is evaluated and recorded by the same experts and staff to avoid errors.

The improvement of upper limb strength of volleyball players by batting training
The change of relative total work of upper limb joints can reflect the characteristics of athletes' power generation during sports.After six weeks of training, first of all, statistical analysis was made on the effect of hitting training on the volleyball players' relative total skill of upper limb joints.The results are shown in Table 1.
The data in Table 1 shows that after the experimental training, the relative total work index of upper limb joints in the experimental group and the control group changes significantly (P<0.05), and the change rate is high.However, the change rate of the control group was significantly lower than that of the experimental group.Table 1 shows that after a period of experimental training, the upper limb strength of the two groups of athletes has been improved to varying degrees.But compared with the control group, the upper limb muscle strength of the experimental group athletes increased more rapidly.This shows that the experimental group uses more force when hitting the ball, which will improve the stability of hitting to a certain extent.

The improvement of volleyball players' physical quality by batting training
In order to further study the impact of batting training on the overall quality of volleyball players, a comparative analysis of the five indicators of the physical quality of the tested players was carried out.The results are shown in Table 2.
It can be seen from the data in Table 2 that after six weeks of experimental training, except for the volleyball throw distance indicators of the control group, the physical quality indicators of the two groups have relatively significant changes compared with those before training (P<0.05).In the experimental group, the two indexes of volleyball throw and push ups changed significantly (P<0.01).In contrast, except for the three indicators of badminton throw, pull up and rope skipping, the change rate of the experimental group and the control group is not much different, the experimental group has significantly improved on the two indicators of volleyball throw and push up.And the overall results of the five indicators of the experimental group are due to the control group.Because badminton throw far, volleyball throw far, push up and pull up are all greatly affected by upper limb strength, the improvement of the experimental group's performance further proves that hitting training has a more obvious effect on volleyball players' upper limb strength than general training.

Training of hitting effect on volleyball players
The hitting standard test is an important means to reflect the training results of experimental objects.After six weeks of experimental training, two professional volleyball coaches were invited to conduct technical evaluation on the standard test of spiking and serving of the two groups.The results are shown in Table 3.
The data in Table 3 intuitively shows that after six weeks of experimental training, the athletes in the experimental group have a large change rate in the four indicators of hitting effect, which has a significant change compared with that before the experiment (P<0.05),among which the expert skill score indicators of spiking have a very significant change (P<0.01).Table 3 proves that batting training is helpful for volleyball players to improve their batting professional skills, especially in the two indicators of spiking and overhand service.At the same time, the traditional volleyball training will also help to improve the overall hitting skills, but the effect is relatively slower, so it is necessary to assist the hitting training in actual training.

DISCUSSION
The batting stage is a very aggressive action, which is characterized by a short time to perform functional actions and requires a certain amount of batting force to complete.The whole power launching process is to take the waist and abdomen as the axis, bend and stretch the trunk, rotate the body, so that the whole body can coordinate the force and drive the arm to swing.Following the principle of the power chain, the power and speed are transferred from the big arm to the small arm, and finally to the palm of the hand to accelerate the hitting of the ball.The process of hitting the ball in the air can be divided into three stages: the first stage refers to the moment when the ground releases to the maximum of the guidance arm when taking off; The second stage is the moment from the maximum movement of the guiding arm to the hitting; The third stage is to hit the volleyball until the ball crosses the net.In the first stage, that is, from the moment of taking off from the ground Before the experiment, the students were randomly divided into experimental group and control group.The experiment lasted for 6 weeks.The training frequency of the two groups of athletes remained the same, three times a week, 80 minutes each time.Besides the formal training, the rest of the preparation activities are the same as the stretching activities, without additional related training.The formal training time in each training process is 60 minutes, including basic physical training, volleyball skill training and confrontation training.The difference between the two groups is that the experimental group mainly conducts hitting training while the control group does not change the traditional volleyball training methods according to the previous training plan.

Table 1 .
The improvement of volleyball players' relative total skill of upper limb joints by batting training.

Table 2 .
The improvement of volleyball players' physical quality by batting training.

Table 3 .
Training of hitting effect on volleyball players.