Introduction

Plyometric training (PT) is popular between individuals involved in dynamic training and PT such as jumping; hopping, skipping and bounding are performed with a goal to increase dynamic performance of muscles (1(. Several study have shown the  programs of PT, to increase physical ability and such training leads to increase of  muscles power and boosts explosive needs in the bodies. Camp et al. (2) have studied the effects of PT on body composition; explosive strength and speed shoot in gat women footballers. The athletes have trained 3 times a week for 12 weeks and finally then study have shown that in the experimental group (PT), a significant increase was seen in the ability to jump after 6 weeks and also shooting speeds increase significantly after 12 weeks, respectively, in this study, the PT have no significant effects on body composition (2). The factors such as power and acceleration have the range of motion exercises that are useful for many sports movement (3). According to previous studies, this method in PT can be currently most useful training   to increase the explosive power in athletes (4, 5) is the requirement for athletes to achieve high levels of performance. Plyometric training is a training strategy designed to improve the performance by incorporating the basic needs of agility and power, allows muscle to reach exponential increase in the maximum strength and speed of movement in the shortest duration (6-9). A study done by Mondal and Wondirad (2014) (10), to assess the effect of 6-week Plyometric training on vertical jump performance demonstrated a significant improvement in the vertical jump performance of an athlete (11). Also, Asadi(2013), in his study concluded that a 6-week in season Plyometric training program had positive effects for improving power and agility, performance in young male basketball players (12). However, other research demonstrates that PT has positive effect on the vertical jump (13, 14,15).

Researchers have reported some improvements regarding the advantage of greater speed, a great deal of research has focused on the development of Sprint performance using a myriad of training methods, including speed training, sprint drills, sprinting against resistances, weight training, combined resistance and speed training, and PT (16). The effects of PT may be different depending on the various subjects’ characteristics, such as strength training level (17), gender (1), age (18, 19), sport activity. Researchers have used several combinations of these variables (16); therefore, it is unclear to consider the optimal combination of these factors for maximum achievement. In addition, meta-analyses can be applied for the factors partly responsible for the variability in treatment effects Observed among different training studies (1, 16). PT has been applied in numerous studies, and there is a general consensus that it improves sport specific skills such as agility (3). Thus the aim of this study was to investigate the effect of short term Plyometric training Program on sprint, strength, and power and agility performance in non-athletic men.

Materials and Methods 

Participants

This quasi-experimental study, Twenty four males were recruited and randomly assigned to a plyometric training (PL, n= 12) (age = 21.9 ± 1.7 years; body mass = 75.2 ± 2.7 kg; body height = 180.6 ± 3.63 cm) or control group (n =12) (age = 22.7 ± 1.4 years; body mass = 78.6 ± 3.1 kg; body height = 180.6 ± 3.7 cm). All participated in the training for five weeks and one session each week and 90 minutes of each session. Before any training and testing an oral explanation of the experimental procedures was given to all participants. After this a written informed consent form was signed according to the declaration of Helsinki and subjects agreed to participate in the experiment which was approved by the University Ethics Committee. All participants were familiarized with the test exercises at least one week before the beginning of the experiment. None of the participants reported current injuries of the spine or the lower extremities and no injuries occurred during the experiment.

Procedures

A five-week period was applied for PT program, followed by post-exercise tests, three days after the last training session. During the experiment, all participants continued their regular training routine, that was identical for every participant and control group did not the exercise tests. All testing sessions began with a standardized aerobic warm up (ten minutes) followed by stretching of the lower extremity muscles. The participants warmed up with their usual routine for training. This comprised ten minutes jogging, stretching, performing 8 to 10 running drills into different directions, and 4 to 6 sub maximal running strides. The plyometric drills in the experimental group were always executed immediately after the warm-up, before any other training tasks were performed on the given day.

Agility

It has been previously suggested that PT improves specific agility in sports where sudden movements (accelerations, stops and direction changes) are required (20). Two specific agility tests were performed in the present study. The T agility test (TAT) was applied to measure agility during direction Changes such as forward sprints (3). In this test three cones were set five meters apart on a straight line and a fourth cone was placed ten meters from the middle cone, forming a T shape. The Illinois agility test (IAT) was utilized to measure agility during sprints including direction changes without stopping, and running at different angles (3). Additional information about these tests has been reported by Miller et al. (2006). Participants performed two trials of each of the agility tests with five minutes recovery between trials, and ten minutes recovery between test types. The best time of the two trials was considered for later analysis. Times to complete the agility tests were measured every time by the same three assisting people using a stop watch. The times average were measured by the three assistants for statistic analysis. Until the end of the study the experimental status of the participants (PL or control) was unknown for all assistants.

Strength performance

Sit Ups Test

The athlete warms up for 10 minutes and lies on the mat with the knees bent, feet flat on the floor and their hands on their ears where they must stay throughout the test. The assistant holds the athlete’s feet on the ground and gives the command “GO” and starts the stopwatch. The athlete sits up touching the knees with their elbows, then returns back to the floor and continues to perform as many sit-ups as possible in 60 seconds. The assistant keeps the athlete informed of the time remaining and counts also records the number of correct sit-ups completed in the 60 seconds and uses this recorded value to assess the athlete’s performance.

Swedish swimming

The athlete warms up for 10 minutes and lies on the ground, places their hands by the shoulders and straightens the arms (start position). The athlete lowers the body until the elbows reach 90° and then extends the arms to return to the start position and continuous this press-up action, the assistant counts also records the number of correct press-ups completed in the 60 seconds.

Sprint performance

Subjects sprinted on a track for 30 m. In normal play, a sprint usually starts from a standing or jogging position, but in our tests, and subjects began the sprint from a stand position stopwatch, and the end time of 30-meter was recorded. The participants have performed two minute- rest period between each test three times. The best of three trials was recorded.

Power performance

Standing Horizontal Jump

The participant stood motionless with the toes stringed level with the start line and were instructed to push off strongly and jumped forward as far as possible. Participants were allowed the use of a counter movement with arms and body swing. The distance jumped from the start line at take-off to the point where the back of the heel nearest to the take-off line landed was measured in centimeters using a metal tape measure. The test was repeated 3 times, and the maximum distance achieved was recorded in centimeters and used for analysis (21, 22).

Vertical Jump Performance

The vertical jump height was measured with a contact mat system (New test 2000, Finland). All subjects completed a controlled warm-up consisting of jogging and stretching and 3 practice jumps at sub maximal effort. Each subject was allowed 3 test jumps with a 3-minute recovery between each jump. The maximum distance achieved was recorded in centimeters.

Plyometric training

The training program was based on recommendations of intensity and volume from Ba et
al. (23), using similar drills, sets, and repetitions. Training volume ranged from 80 foot contacts to 100 foot contacts per session while the intensity of the exercises increased for four weeks before tapering off during week five as recommended by (24) and used previously in another study (25). The intensity of training was tapered so that fatigue would not be a factor during post-testing. The PT group trained at the same time of day, one day a week, throughout the study. During the training, all subjects were under direct supervision and were instructed on how to perform each exercise. Specific details of the PT program are presented in Table 1.

Table 1: Plyometric Five-week training protocol

Analyses

After confirming the data normal distribution using Kolmogorov-Smirnov test, raw data were analyzed using SPSS version 18 (version 18, SPSS Inc., Chicago, IL) and average data were analyzed using sample t-test independent at a significance level of P<0.05 was considered.

Results

Results of the study showed that, power tests in the PT horizontal jump a significant increase and vertical jump showed no significant increase compared to the control group(p = 0.02 , p = 0.08) (Table 2). Results of the study showed that, in the PT group, 30 meters run test, they showed a significant decrease compared with control group(p = 0.001) (Table 2).  Also agility tests in the PT (Illinois and T agility test) was non-significantly reduced compared with the control group (p = 0.13, p = 0.06) (Table 2).Results of the study showed that in the PT, strength factor (swimming Swedish) increased significantly and sit-ups test increased non-significantly compared with the control group(p = 0.001 , p = 0.18) (Table 2).

Table 2: The effect of Short‐term PT Program on sprint, Strength, Power and Agility Performance

*Significant different between pre-and post-test (P≤0.05)

(Cm=centimeter, S=second)

Discussion

The findings of this study revealed that five weeks of PT would improve power, speed, strength, and agility in non-athletic men. The first finding of the study showed that the PT increased significantly in the horizontal jump test and no significant increase in vertical jump test than the control group. The results of the current research are consistent with are consistent with other studies (19, 13, 26, 27, 28, 29, 15).

Such change in only five weeks in our study strengthens previous evidence that plyometric exercises can improve vertical jump performance in a short period of time (30). As previously suggested, positive changes in power, after such a short training period as in the present study, can be associated with the neural components of adaptation: specifically with an increased neural drive to the agonist muscles and changes in the muscle activation strategies (i.e. improved inter muscular coordination), or changes in the mechanical characteristics of the muscle-tendon complex (31).

These neurophysiologic changes together may improve the ability to store and release elastic energy during the stretch-shortening cycle. Specifically, upon landing after a depth jump, an increased level of pre-activation enables the muscle sarcomeres to maintain their length, while the tendons keep elongating and store elastic energy (32).

The second finding of the study showed that PT is effective on the 30 meters run and reduce its time. This result of the study is according to the findings of Meylen et al (2009), Sedano et al (2011), (18, 15). It appears that in the PT, the speed of converting outward contraction to inward contraction increases, the created tension by the muscle and the production power of the muscle potentially increases, therefore reduce in the time of speed run and improvement in other sports have been partly attributed to the outward-oriented training programs and using elasticity feature of muscles. On the other hand, since in the PT, the muscles are firstly encountered outward contraction and immediately inward contraction and with shortening this phase, stronger inward contraction can be created (33), the potential energy stored in the fibers, in the inward contraction, is released and calls a greater number of muscle cords. Moreover, Thomas, French and Hayes have done their exercises twice a week which appears that three session of exercise a week will have better results and places the optimum pressure upon the player (19).

The third finding of the current research revealed that PT have low effect on the Illinois and T-agility test and reduce its time. Fewer studies examined the effects of PT on specific agility, but results are more consistent in contrast with those obtained from sprint tests. Thomas et al. (19) found that despite that sprint time was unchanged; six weeks of PT significantly improved agility (9%) in semiprofessional adolescent soccer players. The greatest improvement in agility (10%) was found in children soccer players after 8 weeks of PT (1).

Miller et al. (2006) (3) found 5 and 3% improvements in the T agility and Illinois agility tests, respectively, after 6 weeks of PT. These improvements are greater than those obtained in the present study; however, making a comparison is difficult as training status of the participants is not reported in the study by Miller et al. (2006) (3). It appears that the agility beneficial effects after PT can be attributed to neural adaptation, specifically to increase inter muscular coordination. Previous research also demonstrated increased proprioception after PT (34).

The forth finding of the study showed that Swedish swimming test increased significantly in the PT and non-significant increase in sit-ups test compared with the control group. Andrejic et al. (2012) in their study compared the effects of two types of short-term strength training and plyometric combination of power and ready to run in the teen’s basketball payment. The results of this study indicate that this is a short-term plyometric and resistance training program for teenage basketball player improves motor function (35).

Asadi et al. (2012) effect of water and land PT on strength, speed and balance in young basketball players investigated. Finally there were no significant differences between groups in any of the variables plyometric land and in the water there. Possible reasons for this discrepancy in results may differ in duration and intensity plyometric-type exercises, participants are and how to assess anaerobic power (36).

Ronnestad et al. (2008) (38) demonstrated 25% gain in 1RM squat in male Norwegian first league soccer players after 7 weeks of training, but in the program strength and PT were combined, therefore their results are not surprising (37). A suggestion has been made previously that subjects in either good or poor physical condition benefit equally from PT work (38). Therefore training volume of less than 10 weeks and with more than 15 sessions, as well as the inclusion of high-intensity programs, with more than 40 jumps per session, was the strategies that seem to maximize the probability to obtain significantly greater improvements in leg muscle strength (38).

Conclusions

According to the results of the present study, after 5 weeks of plyometric training showed a significant increase in the horizontal jump and swimming Swedish and also a significant decrease in the 30 meters run test. Thus plyometric training has been effective on the physical preparation indices and can improve the non athletes’ performance.

References

1. Impellizzeri FM, Rampinini E, Castagna C, Martino F, Fiorini S, Wisloff U. Effects of plyometric training onsand versus grass on muscle soreness and jumping and sprinting ability in soccer players. Br J SportsMed, 2008; 42: 42‐46.
2. Campo S. Effects of lower limb plyometric training on body composition, explosive strength, and kicking speed in female soccer players. Journal of Strength and Conditioning Research, 2009; 23: 1714 -1722.
3. Miller GM, Herniman J, Ricard MD, Cheatham C, Michael TJ. The effect of a 6-week plyometric training program on agility. J Sports Sci& Med.2006; 5:459-465.
4. Milic V, Nejic D Kostic R. The effect of plyometric training on the explosive strength of leg muscles of volleyball players on single foot and two-foot take off jumps. Physical Education and Sport, 2008; 6: 169 – 179.
5. Stem, JD, Jacobson BH. Comparison of Land aquatic based plyometric training on vertical jump performance, National Library of Medicine, 2007; 21: 568-571
6. Ramachandran S, Pradhan B. Effects of short term two weeks low intensity plyometrics combined with dynamic stretching training in improving vertical jump height and agility on trained basketball players, Indian J PhysiolPharmacol, 2014; 58: 133-36.
7. Santos EJ, Janeira MA, Effects of complex training on explosive strength in adolescent male basketball players, J Stren Cond Res 2008; 22:903-09.
8. Carlson K, Magnusen M, walters P. Effect of various training modalities on vertical jump, Res Sports Med 2009; 17: 84-94.
9. Matavulj D, Kukolj M, Ugarkovic D, Tihanyi J, Jaric S. Effects of plyometric training on jumping performance in junior basketball players, J Sports Med Phys Fitness 2001; 41: 159-64.
10. Mondol S, Wondirad S, Effect of 6-week plyometric training on vertical jump performance of maychew athletes, International J Physical Education, Health and Social Science, 2014; 3: 1-6.
11. King A, Cipriani J. Comparing preseason frontal and sagittal plane plyometric programs on vertical jump height in high-school basketball players, 2010; 24: 2109-14.
12. Asadi A. Effects of in-season short-term plyometric training on jumping and agility performance of basketball players, Sport Sciencesfor Healt, 2013; 9: 133-37.
13. Potach DH, Katsavelis D, Karst GM, Latin RW, Stergiou N. The effect of a plyometric training program on the latency time of the quadriceps femoris and gastrocnemius short-latency responses. National Institutes of Health. 2009; 49: 35-43.
14. Rubley MD, Haase AC, Holcomb WR, Girouard TM, Tandy RD, The effect of plyometric training on power and kicking distance in female adolescent soccer players. National Institutes of Health. 2011; 25: 129-134.
15. Sedano S, Matheu A, Redondo JC, Cuadrado G, Effect of plyometric training on explosive strength, acceleration capacity and kicking speed in young elite soccer players. National Institutes of Health. 2011; 51: 50-58.
16. Saez-Saez De Villarreal E, Gonzalez-Badillo JJ, and Izquierdo M. Low and moderate plyometric training frequency produce greater jumping and sprinting gains compared with high frequency Strength Cond Res. 2008;22: 715–725.
17. Dodd DJ, Alvar BA. Analysis of acute explosive training modalities to improve lower-body power in baseball players. J Strength Cond Res.2007; 21: 1177–1182.
18. Meylan, C and Malatesta, D. Effects of in-season plyometric training within soccer practice on explosive actions of young players. J Strength Cond Res. 2009; 23: 2605–2613.
19. Thomas K, French D, and Hayes PR. The effects of two plyometric training techniques on muscular power and agility in youth soccer players. J Strength Cond Res. 2009; 23: 332–335.
20. Yap CW, Brown LE. Development of speed, agility, and quickness for the female soccer athlete. Strength Cond J, 2000; 22: 9-12.
21. Castro-Pinero J, Artero EG, Espana-Romero V, Ortega FB, Sjostrom M, Suni J, et al. Criterion-related validity of field-based fitness tests in youth: A systematic review. Br J Sports Med. 2010; 44: 934–943.
22. Chaouachi A A, Ben Othman A, Hammami R, Drinkwater EJ, and Behm DG. “The combination of plyometric and balance training improves sprint and shuttle run performances more often than plyometric-only training with children.” The Journal of Strength and Conditioning Research 2014; 28: 401-412.
23. Ba Bs, Par JK, Singh D. effects of a short-term plyometric training program of agility in young basketball players. Brazilian Journal of Biomotricity.2011; 5:271-278.
24. Pauole K, Madole K, Lacourse M. Reliability and validity of the T-test as a measure of agility, leg power and leg speed in college aged men and women. J Strength Cond Res, 2000; 14: 443-450.
25. Miller JM; Hilbert SC; Brown LE. Speed, quickness, and agility training for senior tennis players. Strength and Conditioning. 2001; 5, 62-66.
26. Sedano Campo S, Vaeyens R, Philippaerts RM, Redondo JC, De Benito AM, Cuadrado G. Effect of lower-limb plyometric training on body composition, explosive strength, and kicking speed in female soccer players.National Institutes of Health. 2009; 23: 1714-1722.
27. Martin S, Lue-Chin P, Plyometric training improves power and agility in Jamaica national netball team. National Institutes of Health. 2010; 59: 182-187.
28. Chelly MS, Ghenem MA, Abid K, Hermassi S, Tabka Z, Shephard RJ. Effect of in-season short-term plyometric training program on leg power, jump-and sprint performance of soccer players. National Institutes of Health. 2010; 24: 2670-2676.
29. Santos EJ, Janeira MA. The effect of plyometric training followed by detraining and reduced training period on explosive strength in adolescent male basketball. National Institutes of Health. 2011; 25: 441-452.
30. Markovic G. Does plyometric training improve vertical jump height? A meta-analytical review. Br J Sports Med, 2007; 41: 349-355.
31. Markovic G, Mikulic P. Neuro-musculoskeletal and performance adaptations to lower-extremity plyometric training. Sports Med, 2010; 40: 859-895.
32. Kopper B, Csende Z, Safar S, Hortobagyi T, Tihanyi J. Muscle activation history at different vertical jumps and its influence on vertical velocity. J Electromyogr Kinesiol, 2012; 12:1050-6411.
33. Radcliffe JC, and Farentionos RC. High-powered plyometrics.Human kinetics. 1999; 6.
34. Myer GD, Ford KR, Brent JL, Hewett TE. The effects of plyometric vs. dynamic stabilization and balance training on power, balance, and landing force in female athletes. J Strength Cond Res, 2006; 20: 345‐53.
35. Andrejic O. The effects of a plyometric and strength training program on the fitness performance in young basketball players, Physical Education and Sport, 2012; 10:221 – 229.
36. Asadi A. Effects of six weeks depth jump and countermovement jump training on agility performance, Sport Science. 2012; 5 1: 67‐70.
37. Saez‐Saez de Villarreal E, Requena B, Newton RU. Does plyometric training improve strength performance? A meta‐analysis. J Sci Med Sport, 2010; 13: 513‐522.
38. Ronnestad BR, Kvamme NH, Sunde A, Raastad T. Short‐term effects of strength and plyometric training on sprint and jump performance in professional soccer players. J Strength Cond Res, 2008; 22: 773‐780.