The effect of plyometric exercises on the selected biomechanical parameters of breaststroke among male swimmers aged 10-14

International Journal of Sport Studies. Vol., 4 (3), 277-283, 2014 Available online at http: www.ijssjournal.com ISSN 2251-7502 2014; Science Research Publications The effect of plyometric exercises on the selected biomechanical parameters of breaststroke among male swimmers aged 10-14 Rasoul Mohammadi 1*, Heydar Sadeghi 2, Amir Hossein Barati 3 1- Master in Biomechanics of Sport, lecturer of Faculty of Physical Education and Sport Science, Islamic Azad University Eslamshahr branch (*corresponding authors) 2- Full Professor, Faculty of Physical Education and Sport Science, Kharazmi University 3- Assistance Professor, Physical Education Department, Teacher Training University Shahid Rajaee *Corresponding author, Email: rasool.m1411@yahoo.com Abstract In swimming tournaments, a good swim start can help the swimmer achieve a good record. The present paper aims to compare the effect of two plyometric exercises in water and on land on breaststroke grab and track starts among male swimmers. 20- elite swimmers were divided into in-water and on-land groups. Swimmers performance variables include anaerobic power of hands and legs, 25-meter record, the time of contact of head with water and the time of keeping movement in water, flying distance from the starting point to the end point of contact with water and the distance of continuing movement after entering water using both start techniques, the number of movements of hands and legs in 13 meter breaststroke swimming without start and glide. Mean and standard deviation were used to describe the sample, and MANOVA at P 0.05 was used to determine intergroup difference. A significant difference was seen in the time mean of head contact with water in both start techniques of breaststroke swimming; in addition, there is a significant difference in number mean of hand movements and leg movements in breaststroke swimming as well as the number of hand and leg movements in full 13 meter breaststroke swimming after polymeric exercise in both groups. It seems that plyometric exercises improve and enhance the measured parameters in both on-land and in-water groups, so the use of these exercises to improving swimmers start performance is recommended. The effect of plyometric exercises on the selected biomechanical parameters of breaststroke among male swimmers aged 10-14. Key words: Aquatic Plyometric; Land Plyometric; Start Breast Stroke Swimming. Introduction Since a good swim start boosts the chance to achieve a good record in competitive swimming and Swimming speed in particular, swimmers ought to improve their physical fitness and ability to achieve a decent record. In doing so, it stands to reason that the coach and swimmers develop a good training program and focus on biomechanical, physiological, and psychological factors affecting the performance. Plyometric exercise is a physical exercise defined as an eccentric contraction followed by a rapid concentric contraction which results from a powerful explosive move (Chelly er al., 2010; Ranjbar, 2011). Research on plyometric exercises have found that these kinds of exercises give rise to an improvement in the lower extremities strength (Bebi et al., 1984; Adam, 1986; Martel et al., 2005; Arazi et al., 2011), an increase in the upper extremities power (Ghoyehali, 2001; Ranjbar, 2011), and enhance vertical jumps (Guimaracs et al., 1985; Ghoyehali, 2001; Haghighi Najafabadi, 2007). In order to have a rapid entry into water at the start time, it is essential for the swimmer to have a speedy start and then maintain efficient underwater to reduce horizontal velocity (Ranjbar, 2011). Besides, higher power of leg muscles and enhanced jumping ability may play a part in reducing the start time as well as the overall race time (Gutierrez et al., 2010). Grab (feet standing together 277

and parallel) and track starts (one foot forward and the other back) are techniques commonly used in swimming competitions (Almeida et al., 1999; Robinson et al., 2004; Jorgic et al., 2010). Since the use of appropriate and purposeful exercises can help enhance an athlete s abilities and capabilities (Ranjbar, 2011), and on the other hand, to achieve a decent record in swimming is contingent upon giving a good performance of skills especially the start skill, thus plyometric exercises is a good way to strengthen swimmers leg strength and start parameters. It is well documented that plyometric exercises along with strength training can furnish athletes with better and higher performance (Anderst et al., 1994; Almedia et al., 1999). For instance, Bishop et al. (2009) found that plyometric exercises led to a reduction in the time of 5.5 meter breast stroke swimming as well as the time of head contact with the water. Reviewing their findings, Miller et al. (2007) concluded that doing plyometric exercises both in water and on land resulted in enhanced muscular strength and power. A similar research has also affirmed the effect of these exercises on increased muscular strength (Miller et al, 2002). Technically speaking, other research on swimming and plyometric exercises in water and on land have indicated these kinds of exercises give rise to an enhancement in swim start performance, crawl and backstroke swimming as well as muscular strength (Ghoyehali, 2001; Gutierrez, 2010; Ranjbar, 2011;). It, therefore, is a challenge to figure out which kind of exercise enhances explosive power, and which technique works in water or on land. In retrospect, no research was found to have examined the effect and use of plyometric exercises in water on biomechanical start and breast strokein male swimmers. It seems plyometric exercises can be used alongside technical exercises to improve swimmers performance of start skill. Therefore, supposing plyometric exercises impact on start biomechanical parameters and breast stroke record, the present study aims at examining the effect of plyometric exercises both in water and on land on the selected biomechanical parameters of breast stroke in an elite group of swimmers. Thus, The present paper aims to compare the effect of two plyometric exercises in water and on land on breaststroke grab and track starts among male swimmers aged 10-14. Material and Methods This was a before-after quasi-experimental study. The target population consisted of Tehran elite swimmers aged between 10-14 with over three year experience in this field who could perform these two kinds of swims. 20 subjects were randomly sampled and this way divided into two water (10-subject) and land-based (10-subject) plyometric exercise groups. After granting consent and filling out the health form, subjects general characteristics (age, height, weight, Body Mass Index (BMI), Body Fat Percent) were examined. Using Jackson and Pollak s three point formula (chest, triceps, sub-scapular) and with the aid of caliper, Body Density, as follows, was measured through subcutaneous fat (equation 1) (Matinhomaee et al., 2011): Body density = 1.1125025 0.0013125 (X1) + 0.00000055 (X1)2 0.0002440 (X2) Where X1 = the total sum of chest, triceps, sub-scapular fat, X2 = age. After measuring Body Density, Body Fat Percent was measured using Siri equation. The ratio of mass to the square of height was used to measure BMI. The selected biomechanical parameters are leg explosive power, swimmers hands power, 25 meter record, The time of contact of head with water and the time of keeping movement in water, throwing distance and the distance of continuing movement after entering the water, the number of hand and leg movements of in breast stroke swimming. Vertical jump test and Luis formula was used to measure the explosive power of legs. In the test, athletes each was asked to perform Sargent jump three times, then the highest record was recorded and the values were inserted in the following formula (equation 2) to measure their leg strength (Hadavi, 2009). (2) (Anaerobic power) P = Swimmers hand power was measured in the same way as the leg power was, that is, using the above formula and by calculating the flying distance of medicine ball. To do so, each athlete was asked to throw medicine ball three times and the longest throw distance was counted as his hand power. To measure the record of 25 meter breast stroke, performing each start technique, swimmers swam all the way to the end of the 25 meter long pool as fast as they could and the time measured by the stopwatch was considered the record of each swimmer. Thus, two 25 meter breast stroke records were yielded for each swimmer where the best one was counted. To determine the time of contact of the head with water and the time of continuing movement in water after entry into water, two stopwatches were used where one recorded the time of entry into water and the other the time when head was out of water. The difference between the time of entry to water and the time out of water was calculated as the time of continuing movement underwater. In this test, each swimmer was asked to perform each start technique two times and then the time 278

of entry to water and the time of continuing movement were recorded for each time. Given each start, two times of entry to water and two times of continuing movement were recorded and the best times of entry and continuing movement were counted for each swimmer. To determine the throwing distance and the distance of continuing movement in water, a meter was set up in the edge of the pool, the subjects were asked to perform each start technique two times, and then each performance was measured. To do so, the distance of start platform to the place where the swimmer s head came into contact with water was considered the swimmer s throw distance, afterwards the place where the swimmer s head got out of the water was recorded, and then the difference between the distance of entry to water and the distance of head being out of water was measured as the distance of continuing movement in water. To determine the number of hand and leg movements in breast stroke swimming, swimmers each kicked out a 13 meter distance in breast-stroke for one time (meaning they only used breaststroke legs to swim the distance). Another time they used arms movements to swim the distance and the third time they swam so in breaststroke. Each time the number of legs movements, arms movements and at the third time the total sum of legs and arms movements were counted. After measuring the selected parameters, the subjects participated in a training program and the parameters were re-measured at the end of the training program. Before each training session, the swimmers would did warm up exercises for 10-15 minutes. The program training was made of 6 weeks with 3 sessions in each week; each session would go on for 45 to 60 minutes. The exercises were scheduled based on Bishop et al. (2009) s training schedule, but with some slight modifications in the intensity and volume of the exercises. Mean and standard deviation were used to describe the sample, 1-sample K-S was used to examine the normality of the data, and to determine intergroup difference, we applied MANOVA at P 0.05. Table 1: 6 week plyometric training protocol Week Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Exercise recovery/ repetition/ set Bended knee 2.8 (60) 2.8 (60) 3.6 (60) 3.6 (60) 3.8 (60) 3.8 (60) jump Squat jump 2.6 (60) 2.6 (60) 2.8 (90) 2.8 (90) 3.6 (90) 3.6 (90) Jump to side 2.6 (60) 2.6 (60) 2.8 (60) 2.8 (60) 2.10 (60) 2.10 (60) with one leg Jump depth 1.6 (60) 1.6 (60) 2.4 (90) 2.4 (90) 2.6 (90) 2.6 (90) Jump missile 2.6 (60) 2.6 (60) 3.6 (60) 3.6 (60) 4.6 (60) 4.6 (60) Standing broad jump Standing high jump with medicine ball Vertical swing with dumbbell Right and lefthanded swing with a dumbbell Chest pass with medicine ball The front and rear swing arm with dumbbell Skip throwing the ball over the head of 3.8 (60) 3.8 (60) 3.10 (90) 3.10 (90) 3.12 (90) 3.12 (90) 2.6 (60) 2.6 (60) 2.8 (90) 2.8 (90) 3.6 (90) 3.6 (90) 2.6 (60) 2.6 (60) 2.8 (60) 2.8 (60) 3.6 (60) 3.6 (60) 2.8 (60) 2.8 (60) 2.10 (60) 2.10 (60) 3.8 (60) 3.8 (60) 3.10 (60) 3.10 (60) 3.12 (90) 3.12 (90) 4.10 (90) 4.10 (90) 2.8 (60) 2.8 (60) 2.10 (60) 2.10 (60) 3.8 (60) 3.8 (60) 3.1 (60) 3.1 (60) 4.1 (60) 4.1 (60) 5.1 (60) 5.1 (60) 279

Results Individual characteristics of subjects of control and experiment group are presented in table 2. Pretest results revealed that two groups are homogenous in terms of physical and anthropometric characteristics. Table 2: mean and standard deviation of subjects characteristics variable number Age (year) Height (cm) Weight (Kg) In-water group 10 12.70 ± 1.49 157.70 ± 9.66 53.70 ± 10.37 On-land group 10 13.50 ± 1.08 161.80 ± 5.33 58.30 ± 9.63 As shown in table 3, BMI and Body fat Percent of on-land group were higher than those of in-water group. The mean of swimmers leg power indicates that after a program of plyometric exercise in-water group performance is about 1.4 Kg better than on-land group performance, but no difference was found between two groups subjects (p = 0.999). In regard to arm power, on-land group swimmers outperformed inwater group swimmers by about 1.84 Kg after a program of plyometric training, however no significant difference was revealed between the results of two groups subjects (p = 0.941). Table 3: mean and standard deviation of BMI, Body Fat Percent, arm power and anaerobic power after and before plyometric exercise Group Parameter water land BMI (Kg/square meter) 21.58 ±3.72 21.52 ± 3.63 22.39 ± 3.42 *22.32 ± 3.45 Body Fat Percent 5.61 ± 3.54 15.06 ± 3.60 16.94 ± 1.59 *16.27 ± 4.36 Arm power (Kg) 5.91 ± 5.13 37.92 ± 5.68 37.54 ± 3.52 *39.76 ± 3.78 Leg anaerobic power (Kgmeter 9.29 ± 1.09 9.88 ± 1.06 9.89 ± 1.02 * 10.48 ± 1.19 per second) Swimmers performance variables pertaining to grab and track starts in breaststroke are presented in table 4. The most variation goes to the mean of the 25 meter breaststroke in track start and in-water group outperformed on-land group reducing the record of 25 meter by nearly 0.4 seconds. According to the results, no significant difference was revealed between in-water and on-land groups in terms of grab start (p = 0.945) and track start (p = 0.826). Concerning the mean of the time of head contact with water in grab and track starts, there was a significant difference in in-water group (p = 0.007, p = 0.000) so that the mean of the time of swimmers head contact with water in grab and track starts was respectively reduced by 20.99 and 18.69 percent after a program of plyometric training. On-land group, however, no difference was found in the time of the head contact with water in both grab and track starts (p = 0.180, p = 0.169).Regarding the mean of the time of continuing movement after entry to water, no difference was found in on-land and in water groups in grab start (p = 0.117, p = 0.172) and track start (p = 0.278, p = 0.068). in regard to the throw distance from the start point to the point of contact with water, there was an increase in grab start (in water group about 4.32, on land group about 4.03) as well as in track start (in water group about 4.22, on land group about 6.06). However, there was no significant difference between grab start (p = 0.977) and track start (p = 0.749) in onland and in-water groups. In regard to the mean of the distance of continuing movement in water, there was also no significant difference in grab start (p = 0.939) and track start (p = 0.930) in both on-land and in-water groups after the course. 280

Table 4: mean and standard deviation of swimmers performance variables in breaststroke Grab and track starts before and after plyometric exercises parameter group water Land Type of start Pre-test Post-test Pre-test Post-test 25 meter record (second) Time of head contact with water (second) Time of continuing movement in water after entry to water (second) Throw distance from start point to point of head contact with water (meter) Distance of continuing movement in water after entry to water (meter) Grab 25.13±2.18 33.44±2.72 24.48±3.14 22.92±3.44 Track 25.23±2.35 23.31±2.48 24.52±3.18 23±3.32 Grab 0.97±0.09 0.76±0.10 0.93±0.21 *0.80±0.17 Track 1.01±0.17 0.82±0.10 0.91±0.22 *0.84±0.12 Grab 3.91±0.59 3.52±0.63 4.08±0.38 *3.81±0.34 Track 3.69±0.54 3.55±0.50 2.66±0.23 *2.78±0.26 Grab 2.66±0.23 2.78±0.26 2.73±0.29 0.32±2.84 Track 2.61±0.19 2.72±0.20 2.64±0.25 0.32±2.80 Grab 5.63±0.55 5.83±0.61 5.23±0.82 0.83±5.3 Track 5.41±0.37 5.62±0.39 5.05±0.94 0.95±5.22 As shown in table 5, it was revealed that there as a significant difference in the number of hands, the number of legs, and the number of hands and legs movements in the 13 meter breaststroke in both on-land and in-water groups after the plyometric exercises, that is, the mean of breaststroke hands and breaststroke legs in on-land and in-water groups was respectively reduced by p = 0.017, p = 0.028, and p = 0.025, p = 0.017. The mean of hands in full breaststroke and legs in full breaststroke in in-water and on-land groups was respectively reduced by p = 0.010, p = 0.025, and p = 0.009, p = 0.025. Table 5: mean and standard deviation of number of breaststroke hands and legs in the first 13 meters before and after plyometric exercises variable water land Breaststroke swimming hands legs hands full breaststroke legs in full breaststroke Pre-test Post-test Pre-test Post-test 7.70±1.06 6.50±0.97 7.60±1.27 6.30±1.16 7.20±1.23 6±0.94 7.30±1.25 6±0.94 5.80±0.92 5±0.47 6.20±1.03 5±0.82 5.80±0.92 5±0.47 6.10±0.88 5±0.82 Discussion and conclusion The present paper aimed to investigate the effect of a program of plyometric exercises in water and on land on the selected biomechanical parameters of breast stroke start among an elite group of male swimmers. The findings revealed that the subjects in both groups demonstrated enhanced leg power, however no significant difference was found in the swimmers leg anaerobic power after the program which is in accord with other studies (Ghoyehali, 2001; Martel et al, 2005; Haghighi Najafabadi, 2007; Miller et al, 2007; Ranjbar, 2011). We didn t find any significant difference in the post-test which could probably be because of subjects immaturity, the level of subjects skill, age, or training load. Compared with the previous research, the present research revealed that plyometric exercises can improve leg s anaerobic power and therefore can 281

be recommended for leg s power enhancement. The subjects of both on-land and in water groups showed enhanced arm s power, but in comparison with the pre-test, no significant difference was found in the two groups subjects enhanced performance. Literally, the enhancement in strength demonstrates that the subjects arm in on-land group outperformed in-water group which is consistent with Ranjbar s (2011) findings as well as Robinson et al. s (2004) study reporting that on-land group outperformed in-water group. Considering the previous research and the present one, we recommend using plyometric exercises to enhance arm s strength. The 25 meter breaststroke record in both groups decreased numerically and this enhancement was better in in-water group s performance than in on-land group s in terms of track and grab starts. Although the findings show no significant difference between two groups in terms of grab and start techniques after the program, this is in agreement with Ranjbar s (2011) study, Ghoyehali s (2001) research, and Bishop s et al. (2009) study. Given the effect of plyometric exercises on reducing swimmers record, it is recommended for athletes. In regard to the throw distance from the start point to the point of head contact with water, both in-water and on-land groups were revealed to have better performed in grab start than in track start. The performance of in-water group was rather considerable in grab start. We also found enhanced performance in the throw distance in both groups and this enhancement was more considerable in in-water group and in grab start. Based on the findings, it can be inferred that plyometric exercises had no effect on the throw distance from the start point to the point of head contact in water and the distance of continuing movement in water after entry to water in start and grab starts among the swimmers of both groups. This was in accord with the findings of Ranjbar (2011), and Bishop et al. (2009). This insignificance could probably be attributed to the subjects immaturity, the level of subjects skill, age, or the training load. Since plyometric exercises positively affect the explosive power of legs, they may be useful for start platform jump. The findings revealed that there was a significant difference in the mean of the time of head contact with water among the swimmers of in-water group in grab and track starts and this reduction was more tangible in grab start. In spite of a reduction in the means, however, no differencewas found in the mean of the time of head contact with water as well as the time mean of continuing movement in water among the swimmers of on-land group in grab and track starts after the course, in the time mean of continuing movement in water after entry to water among the swimmers of on-land group in breaststroke garb and track starts after the course; There was also no significant difference in the time mean of continuing movement in water after entry to water in breaststroke grab and track starts after the mixed method of plyometric exercises in water and on land. Generally speaking, it seems that plyometric exercises significantly affect the time of continuing movement in water after entry to water in breaststroke grab and track starts in both groups as well as the time of head contact with water in on-land group, resulting in a reduction in the time which isn t in accord with the findings of Ranjbar (2011), but in accord with the findings of Bishop et al. (2009). Bishop et al. (2011) reported a significant enhancement and reduction in the time of head contact with water and continuing movement among the swimmers after training. To determine the effect of two kinds of plyometric exercises in water and on land on swimmers performance in breaststroke swimming, we, here, separately measured the number of hands, the number of legs, and the number of hands and legs together in full breaststroke swimming. 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