INTERVAL TRAINING EFFECTS ON CARDIORESPIRATORY CAPACITY OF SWIMMERS

ABSTRACT Introduction: Cardiopulmonary function is directly related to the body's ability to perform metabolism under aerobic conditions. It is a key characteristic for the training of professional swimmers. It is believed that adding interval training to traditional workouts may contribute to the aerobic endurance of these athletes. Objective: Evaluate the interval training effects on the cardiorespiratory capacity of swimmers. Methods: Twenty volunteer swimmers were randomly divided into two groups for seven weeks. There were 4 hours of class per week, totaling 28 hours of training. In the formal training stage, the experimental group performed intermediate-intensity training, while the control group continued to perform traditional swim team training. The experimental indicators pertinent to the evaluated athletes were collected, tested, and analyzed before and after the experiment. Results: The VO2 of the athletes in the experimental group increased from 3.90±0.67L/min before the experiment to 4.06±0.73L/min after the experiment; VE increased from 156.08±35.76L before the experiment to 180.08±39.42L after the experiment; underwater endurance time increased from 46.80±8.43s before the experiment to 55.49±7.60s after the experiment. Conclusion: Intermittent training improves athletes' physical fitness and sports capacity, being an effective method to improve cardiopulmonary function. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.


INTRODUCTION
Compared with other sports, swimming requires a higher level of cardiopulmonary function. 1Because the body is almost completely immersed in water during swimming, the water resistance is much greater than that in the land environment.Therefore, a specific distance in water consumes more oxygen and physical strength than the same distance on land. 2 Therefore, the quality of cardio pulmonary training will also affect the swimming performance, which is why more and more sports academics are studying the improvement of lung capacity in the swimming training center to learn how to quickly improve the vital capacity, breathe more regularly and swim more easily. 3Many scientific researches have shown that exercise ability is closely related to cardiorespiratory function, so we can take cardiorespiratory function as a standard to evaluate a person's exercise ability and health status. 4 Sports practice shows that high-intensity interval training can increase the maximum oxygen uptake of athletes, improve cardiopulmonary function, and reduce body fat.Intermittent exercise is used by athletes to maintain high physiological response and achieve better results in many sports fields. 5The significance of this study is to observe the changes of cardiorespiratory function of swimmers through a certain interval training, so as to provide a reference for improving the training performance of swimmers in many aspects. 6

METHOD Selection of experimental objects
According to the research purpose and research focus, 20 amateur swimmers aged 17-19 were selected from a swimming club in a city before the experiment began, and all of them had been in sports for more than 7 years.The study and all the participants were reviewed and approved by Ethics Committee of Gannan Normal University (NO.GANNUF082).In order to ensure the smooth implementation of the experiment and the safety of the tested athletes, we confirmed with the coaches and athletes that they are in good physical condition and have no physical diseases in the near future, so we can participate in the experiment process.On the basis of understanding the purpose of this experiment, the consent form was signed and the pre experiment test was conducted.The athletes were divided into groups according to the principle of randomization.The basic information of the experimental group and the control group is shown in Table 1.
From the basic information data of the tested athletes in Table 1, there is no significant difference in age, height, weight and training years between the selected experimental group and the control group, which meets the basic requirements of this experiment.

Experimental control
The experiment lasts for 7 weeks, with 4 class hours per week and 28 class hours in total.The weekly training time is Monday, Wednesday, Thursday and Saturday.Each class hour is 90 minutes, mainly including 20 minutes of preparation activities, 50 minutes of formal training and rest intervals, and 20 minutes of relaxation after training.The preparation and relaxation activities of the experimental group and the control group are basically the same.In the formal training stage, the experimental group mainly conducts intermediate intensity interval training, while the control group does not change according to the original traditional training mode of the swimming team.The intermittent exercise of the experimental group was controlled at medium intensity according to the load of 17-19 year old athletes, and the height of the running platform used for training was consistent.Before and after the experiment, the relevant experimental indicators of the tested athletes were tested and recorded.The experimental equipment and measurement methods used were checked by professionals, and the recording staff were the same before and after the experiment.
During the experiment, in order to ensure the effectiveness of the experiment and avoid the influence of external factors as much as possible, except for special circumstances, the tested athletes did not miss classes at will, and successfully completed the relevant training according to the established training plan.In addition, the daily diet and living habits of the athletes were relatively consistent during the experiment.In addition to the weekly experimental training, do not carry out additional high-intensity exercise training, and try to keep adequate sleep and regular work and rest.

Experimental indicators and test methods
The measurement of the direct indexes of the cardiopulmonary capacity of the tested athletes mainly includes VO2 (oxygen uptake), V02/kg (kg oxygen consumption), VE (ventilation per minute) and HR (heart rate).The oxygen consumption and ventilation were measured with the CORTEX cardiopulmonary function instrument made in Germany and mercury 4.0 treadmill.During the measurement process, the test athletes are required to first carry out 5 minutes of preparatory activities, set the running platform to a slope of 2 °, and the speed of 5 km/h starts to increase gradually, increasing the speed of 1 km every 2 minutes until the strength limit position of the test subjects.The heart rate test uses the pulse test method in the quiet state, and the maximum heart rate under the exercise conversion is continuously monitored by the POLARRS800 heart rate meter made in Finland, which can monitor the maximum heart rate value under the exercise limit state.The indirect indexes of cardiopulmonary capacity of the tested athletes mainly include explosive force, endurance and underwater air holding time.The explosive force mainly measures the standing long jump and solid ball throwing.The solid ball is thrown in a sitting position.When holding the ball, hold both sides of the ball, and throw the ball from the back of the head upwards at an angle of 45 ° with the force of stepping on the ground and swinging the arm.Sport endurance mainly measures push ups and 1.5 mile running results.The equipment required for indirect indicator measurement mainly includes meter ruler, stopwatch, solid ball and yoga mat for sports.
The relevant indicators were measured in the indoor gymnasium used by athletes during training.The temperature was controlled at about 25 o C and the relative humidity was maintained at about 40%.

The direct index of interval training on the improvement of swimmers' cardiopulmonary capacity
After 7 weeks of experiment, this paper first measured the four indexes of the tested athletes' cardiopulmonary capacity, and compared them with the results before the experiment.The measurement results of VO2, V02/kg, VE and HR of test athletes are shown in Table 2.
Therefore, according to the results in Table 2, after a period of training, whether intermittent training or basic swimming training methods, the cardiorespiratory function of athletes be significantly improved.But in contrast, intermittent exercise with a certain intensity can provide more obvious improvement.Swimming has a high demand on cardiorespiratory function, so appropriate interval training can be applied to daily training to improve the cardiorespiratory function of athletes.

Indirect indicators of interval training for improving swimmers' cardiopulmonary capacity
In addition to the basic indexes of cardiopulmonary function, the indexes of exercise ability related to swimming can also indirectly reflect whether the cardiopulmonary function of the tested athletes has changed.Therefore, after the experiment, the explosive force, sports endurance and underwater breathing time of the athletes were tested.The results of the three indicators are shown in Table 3, Table 4 and Table 5 respectively.
The comparison results of the impact of interval training on swimmers' explosive power before and after the experiment are shown in Table 3.
The data in Table 3 shows that moderate intensity interval training can significantly improve the explosiveness of swimmers.Because the intensity of intermittent training is higher than that of general training, and the alternating exercise and rest exercise has a strong effect on the cardiopulmonary function of the subjects, the improvement of cardiopulmonary and sports functions is conducive to the enhancement of muscle explosive force.The general training conducted by the control group is more to improve the physical quality of the subjects as a whole, and has less effect on improving the special function of explosive force.
The exercise endurance of the tested athletes was compared before and after the test, and the results are shown in Table 4.
Table 4 shows that the intermediate intensity interval training has a significant effect on improving the exercise endurance of the subjects, while the improvement effect of general physical fitness training is limited.In the training process of swimmers, targeted interval training can be appropriately increased, which has a significant effect on improving the overall sports ability of swimmers.
In order to further verify the effect of interval training on the specific sports ability of swimmers, the time of underwater breath holding was tested.The comparison results before and after the experiment are shown in Table 5.

Table 1 .
Basic information of experimental group and control group.

Table 2 .
Effect of interval training on ventilatory capacity and heart rate of swimmers.

Table 3 .
The effect of interval training on the explosiveness of swimmers.

Table 4 .
The Effect of Interval Training on Swimmers' Sports Endurance.

Table 5 .
Effect of Interval Training on Underwater Breath Retention of Swimmers.