IMPACTS OF RESISTANCE EXERCISE ON PERFORMANCE IN SWIMMERS

ABSTRACT Introduction: The need for strength of the lower limbs to provide absolute speed in competitive-level swimmers requires methodological and evidence-based training. Resistance training is an effective way to increase muscle strength and it is believed that it can be adapted to benefit swimmers. Objective: Study the impacts of lower-limb resistance exercise on the sport performance of swimming athletes. Methods: Twelve volunteer athletes were selected for the experiment, randomly divided between experimental and control groups. There was no significant difference between the two groups. The experimental group received intervention with lower limb resistance training, while the control continued with routine physical training. Results: The thigh circumference of the experimental group increased from 56.01±5.40 cm to 57.14±5.06 cm; the Dive angle decreased from 44.85±6.74 to 43.23±7.71; the Entry distance increased from 3.51±0.36 m to 3.69±0.39 m; flight time was reduced from 0.33±0.05 s to 0.31±0.07 s; freestyle performance was reduced from 28.90±2.40 s to 27.18±2.72 s. Conclusion: The training with resistance exercise in the lower limbs showed evident improvements in the swimmers’ physical performance, besides the evident gain of muscle mass. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.


INTRODUCTION
Swimming mainly depends on the swing of the limbs, and the lower limbs are the main source of strength of the limbs in the water. 1 The balance and swimming in the water environment are realized through the action of the lower limbs beating and kicking on the water, while maintaining a high body position.And good kick is also an important factor to reduce resistance in water.Previous studies have shown that resistance training is an effective way to increase the physical muscle strength of athletes, and has a certain impact on improving the overall physical quality and sports performance. 2Lower limb resistance training is a training method that focuses on the lower limb muscles of the body.It has a significant effect on transferring the core muscle group and enhancing the lower limb muscle strength and body balance ability. 3In the process of lower limb resistance training, the tensile strength of muscles and ligaments can be effectively expanded by resisting the resistance brought by sports equipment.Resistance exercise with appropriate resistance and frequency can increase the cross-sectional area of muscle fibers, thus achieving the effect of shaping. 4At the same time, the resistance training of the lower limbs will also exercise the muscles of the whole body except the muscles of the lower limbs, and also have a certain impact on the cardiopulmonary function. 5According to the characteristics of swimming, combined with the professional needs of swimming, this study designed and conducted a control experiment with lower limb resistance training as a variable. 6By studying the relevant effects of lower limb resistance training on athletes, some suggestions are provided to better improve the performance level of athletes.

METHOD Research object
According to the purpose of the experiment and the research method, this paper chooses the method of control experiment to carry out the relevant research.The subjects were selected from a swimming club in a city, and the athletes aged between 16 and 20 were randomly selected for investigation.The study and all the participants were reviewed and approved by Ethics Committee of Jiangsu College of Nursing (JSCN2289SR).In order to ensure the accuracy of the final experimental results, after sorting out the basic information, 12 athletes were selected to carry out the experiment, excluding the athletes who could not participate in the experiment for various reasons.12 athletes were randomly divided into experimental group and control group.See Table 1 for the basic information of the age, height, weight and training years of the two groups of subjects.

Experimental ideas
The experiment lasted for 8 weeks.The experimental equipment used in this experiment mainly includes FMS test kit, electronic scale, tape measure, stopwatch, camera and tripod.The experimental equipment used in the exercise process mainly includes dumbbells, steps and yoga mats for lower limb resistance training in the experimental group.All tests and training are conducted in the swimming pool and gymnasium of the club.

Improvement of swimmers' physical quality through lower limb resistance exercise
First of all, by analyzing the changes of swimmers' lower limb circumference, the effect of lower limb resistance exercise on the improvement of swimmers' physical quality is explored.The results are shown in Table 2.
The data in Table 2 shows that after 8 weeks of lower limb resistance training, the thigh dimensions of the tested athletes in the experimental group changed significantly.The thigh circumference increased from 56.01 ± 5.406cm before training to 57.14 ± 5.060cm after training; The change of calf circumference was not obvious, only a small range was reduced, from 37.58 ± 3.700cm before the test to 37.21 ± 3.346cm after the training.The change in the control group was more obvious, and the trend was opposite to that in the experimental group.The thigh circumference decreased from 57.22 ± 6.340 cm before training to 56.20 ± 6.125 cm after training; The calf circumference increased from 37.74 ± 3.594cm before the test to 38.60 ± 3.510cm after training.

Improvement of swimmers' movement skills through lower limb resistance exercise
After testing the changes of swimmers' movement skills, the data of each index are shown in Table 3, Table 4 and Table 5.
The data in Table 3 shows the impact of lower limb resistance exercise on distance indicators of swimmers.
It can be seen from the data in Table 3 that the water entry distance of the experimental group shows an increasing trend after training, compared with the control group, there is no significant change.The water entry distance of the experimental group was increased from 3.51 ± 0.366m before training to 3.69 ± 0.398m after training, and the sliding distance was increased from 11.34 ± 1.316m before training to 11.60 ± 1.367m after training.Since the lower limb resistance training will improve the strength of the lower limb muscles, the water entry distance and sliding distance largely depend on the explosive force of the swimmer when kicking, the lower limb resistance training has obvious effect on the improvement of the water entry distance and sliding distance of the swimmer.
In addition, the angle indicators of swimmers are measured, and the results are shown in Table 4.
The take-off angle and entry angle of swimmers are the important factors that affect the glide speed of swimmers.The smaller the angle of taking off and entering the water, the easier it is for athletes to start swimming.It can be seen from Table 4 that after training, the takeoff angle of the experimental group changed slightly, only slightly, but the water entry angle changed greatly, from 44.85 ± 6.747 before training to 43.23 ± 7.717 after training.In contrast, the two indicators in the control group did not change significantly.
The measurement results of the time indicators of the tested athletes are shown in Table 5.
As can be seen from the data in Table 5, after 8 weeks of training, the flight time of the experimental group changed greatly, from 0.334 ± 0.0598s before training to 0.319 ± 0.0709s after training.The departure time changed little, only the mean value decreased slightly, from 0.587 ± 0.0407s before training to 0.579 ± 0.0497s after training.The departure time of the control group did not change significantly, but the flight time increased to a certain extent, from 0.328 ± 0.0304s before training to 0.346 ± 0.0298s after training.

Improvement of swimmers' performance level by lower limb resistance exercise
In addition to testing the movement skills of the tested athletes, a comparative analysis of the performance level of the tested athletes was carried out, and the results are shown in Table 6.
The data in Table 6 shows that resistance training and general physical training can improve athletes' performance to a certain extent.However, there will be certain differences according to the athletes themselves and the different sports.Therefore, the two can be organically combined during training to maximize the overall performance of athletes.

DISCUSSION
The change of body composition is mainly reflected in the change of skeletal muscle mass.Resistance training usually has a positive effect on the enhancement of muscle strength and circumference, which is mainly reflected in the increase of the cross section volume of single muscle cell and whole muscle due to the increase of the number and During the 8-week training period, all subjects were given the same swimming skill training and training warm-up and relaxation exercises.The difference was only when the experimental group received the intervention training of lower limb resistance movement, while the control group received the basic physical training according to the previous swimming training.The resistance movement of lower limbs mainly includes dumbbell squat, dumbbell step climbing and elastic lunge walking.Focus on training the gluteus, quadriceps and hamstring muscles of the athletes in the experimental group.The exercise frequency of the two groups of athletes remained the same.They trained once a day on Monday, Tuesday, Thursday and Friday, with a training duration of 2 hours, including warm-up exercise before training and stretching exercise after training.

Table 1 .
Sorting out the basic situation of swimmers in this paper.

Table 2 .
Effect of lower limb resistance exercise on swimmers' lower limb circumference.

Table 3 .
The Effect of Resistance Exercise of Lower Extremities on Distance Index of Swimmers.

Table 4 .
Influence of lower limb resistance exercise on swimmers' angle index.