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©Journal of Sports Science and Medicine (2006) 5, 459-465 Research article THE EFFECTS OF A 6-WEEK PLYOMETRIC TRAINING PROGRAM ON AGILITY Michael G. Miller ▯, Jeremy J. Herniman , Mark D. Ricard , Christopher C. 2 Cheatham and Timothy J. Michael 1 1Department of HPER, Western Michigan University, MI, USA 2University of Texas-Arlington, USA Received: 21 June 2006 / Accepted: 07 August 2006 / Published (online): 01 September 2006 ABSTRACT The purpose of the study was to determine if six weeks of plyometric training can improve an athlete’s agility. Subjects were divided into two groups, a plyometric training and a control group. The plyometric training group performed in a six week plyometric training program and the control group did not perform any plyometric training techniques. All subjects participated in two agility tests: T-test and Illinois Agility Test, and a force plate test for ground reaction times both pre and post testing. Univariate ANCOVAs were conducted to analyze the change scores (post – pre) in the independent variables by group (training or control) with pre scores as covariates. The Univariate ANCOVA revealed a significant group effect F2,2625.42,p=0.0000fortheT-testagilitymeasure.FortheIllinoisAgilitytest,a significant group effect2,2627.24,p=0.000wasalsofound.Theplyometrictraininggrouphad quicker posttest times compared to the control group for the agility tests. A significant gro2,26ffect F = 7.81, p = 0.002 was found for the Force Plate test. The plyometric training group reduced time on the ground on the posttest compared to the control group. The results of this study show that plyometric training can be an effective training technique to improve an athlete’s agility. KEY WORDS: Jumping, training, performance variables, quickness. INTRODUCTION strength-training program, can contribute to improvements in vertical jump performance, Plyometrics are training techniques used by athletes acceleration, leg strength, muscular power, increased in all types of sports to increase strength and joint awareness, and overall proprioception (Adams, explosiveness(Chu, 1998). Plyometrics consists of a et al., 1992; Anderst et al., 1994; Bebi et al., 1987; rapid stretching of a muscle (eccentric action) Bobbert, 1990; Brown et al., 1986; Clutch et al., immediately followed by a concentric or shortening 1983; Harrison and Gaffney, 2001; Hennessy and action of the same muscle and connective tissue Kilty, 2001; Hewett et al., 1996; Holcomb et al., (Baechle and Earle, 2000). The stored elastic energy 1996; Miller et al., 2002; Paasuke et al., 2001; within the muscle is used to produce more force than Potteiger et al., 1999; Wilson et al., 1993). can be provided by a concentric action alone Plyometric drills usually nilt,g (Asmussen and Bonde-Peterson, 1974; Cavagna, starting, and changing directions in an explosive 1977; Komi, 1992; Miller, et al., 2002; Pfeiffer, manner. These movements are components that can 1999; Wathen, 1993). Researchers have shown that assist in developing agility (Craig, 2004; Miller et plyometric training, when used with a periodized al., 2001; Parsons et al., 1998; Yap et al., 2000; m u i d e M 6 Miller et al. 461 any type of plyometric training at the time of the directions, and run at different angles. These tests study. were selected based upon established criteria data for males and females and because of their reported Procedures validity and reproducibility of the tests (Pauole et All subjects agreed not to change or increase their al., 2000; Roozen, 2004). Finally, a force plate test current exercise habits during the course of the (Figure 3) was used to measure quickness and power study. The plyometric training group participated in (ground contact time while hopping). This test was a 6-week training program performing a variety of created to mimic the dot drill that requires an athlete plyometric exercises designed for the lower to stay balanced in order to shift their body weight in extremity (Table 2), while the control group did not several different directions. participate in any plyometric exercises. All subjects were instructed not to start any lower extremity strengthening programs during the 6-week period and to only perform activities of normal daily living. Prior to the study, procedures and guidelines were presented orally and in written form. Subjects agreeing to participate signed an institutionally approved consent form. A 6-week plyometric training program was developed using two training sessions per week. The training program was based on recommendations of intensity and volume from Piper and Erdmann (1998), using similar drills, sets, Three cones are set five meters apart on a and repetitions. From a physiological and straight line. A fourth cone is placed 10 meters psychological standpoint, four to six weeks of high from the middle cone so that the cones form a T. intensity power training is an optimal length of time ▯ Athlete starts at the base of the “T” for the CNS to be stressed without excessive strain ▯ Examiner gives signal to go and when athlete or fatigue (Adams et al., 1992). It is the belief of crosses the photocell the time begins. some sports physiologists that neuromuscular ▯ Athlete runs to middle cone and touches it. adaptations contributing to explosive power occur ▯ Athlete side steps 5 meters to the right cone early in the power cycle of the periodization phase and touches it. of training (Adams et al., 1992). Plyometrics were ▯ Athlete side steps 10 meters to the far cone only performed twice per week to allow for and touches that one. sufficient recovery between workouts as ▯ Athlete side steps 5 meters back to the middle recommended by researchers (Adams et al., 1992). cone and touches it. Training volume ranged from 90 foot contacts ▯ Athlete runs 10 meters backwards and touches to 140 foot contacts per session while the intensity the cone at the base of the T. of the exercises increased for five weeks before ▯ Time stops when athlete crosses the photocell. tapering off during week six as recommended by Figure 1. T-Test procedures. Piper and Erdmann (1998) and used previously in another study (Miller et al., 2002). The intensity of Prior to training, all subjects had their baseline training was tapered so that fatigue would not be a agility tested, using the three tests previously factor during post-testing. The plyometric training mentioned. The total testing session was group trained at the same time of day, two days a approximately one hour for each subject which week, throughout the study. During the training, all included warm-up, ten minute rest times between subjects were under direct s uesnadw e tests and approximately three minutes between reps. instructed on how to perform each exercise. Each test was explained and demonstrated. Before testing, subjects were given practice trials to become Testing procedures familiar with the testing procedures. All tests were Three tests conducted both pre and post training counterbalanced pre and post testing to ensure that were used to determine agility outcomes. The T-test testing effects were minimized. Subjects performed (Figure 1) was used to determine speed with each test 3 times and the results were averaged. directional changes such as forward sprinting, left and right side shuffling, and backpedaling. The Statistical analysis Illinois agility test (Figure 2) was used to determine Pre and post values for the dependent variables were the ability to accelerate, decelerate, turn in differenanalyzed to determine if the distributions were 462 Agility and plyometrics normal using Kolmogorov-Smirnov goodness-of-fit Tests of normality indicated that dependent variables test and the Shapiro-Wilk Normality test. Change were normally distributed. The single factor scores (post – pre) were computed for each of the ANCOVA revealed a significant group effect F = 2,26 dependent variables: T-Test agility, Illinois Agility 25.42, p = 0.000, power = 1.00 for the T-test agility Test and the force plate test. Single factor measure change score, when controlling for Pre-test ANCOVAs were used to test for differences differences. As shown in Table 3, the plyometric between groups (Control, Plyometric Training) for group improved their T-Test agility times by ▯0.62 ± the dependent variable change scores using the pre- 0.24 sec, while the control group times were test values as a covariate. Alpha was established a virtually unchanged 0.01 ± 0.14 sec. For the Illinois priori at p < 0.05. The Statis tical Package for SociaAgility test change score, a significant group effect Science (version 11.0: Chicago, Ill) was used to F =27.24,p=0.000,power=1.00wasfound, 2,26 calculate the statistics. when controlling for Pre-test differences. The plyometric training group improved their Illinois Agility Test times by ▯0.50 ± 0.32 sec and the control group times changed by ▯0.01 ± 0.05 sec. A significant group effect F2,26=7.3,p.02, B C power = 0.923 was found for the force plate test change score, when using the Pre-test values as a covariate. The plyometric training group improved their force plate agility test times by ▯26.37 ± 21.89 msec and the control changed their times by ▯0.98 ± 6.33 msec, see Table 3. A D START FINISH ▯ Test is set up with four cones forming the agility area (10 meters long x 5 meters wide). Cone at point A, marking the start ▯ Cone at B & C to mark the turning spots ▯ Athlete starts in the center force plate. ▯ Athlete balances on dominant leg. ▯ Cone at point D to mark the finish. ▯ Place four cones in the center of the testing ▯ Athlete jumps from center forward and back area 3.3 meters apart. to the center ▯ Start lying face down with the hands at ▯ Then to the right and back to the center ▯ Then backwards and back to the center shoulder level. ▯ On the “go” command, athlete begins and ▯ Then left and back to center time starts when they cross the photocells. Figure 3. Force Plate Agility procedures. Force ▯ Get up and run the course in the set path (left Plate – going clockwise on dominant foot. to right or right to left). ▯ On the turn spots B and C, be sure to touch DISCUSSION the cones with your hand. For the T-test, times were improved by 4.86%, for ▯ Trial is complete when you cross the finish line and when no cones are knocked over. the Illinois agility test, 2.93%, and for the force Figure 2. Illinois Agility Test procedures. plate, subjects improved by over 10%. By finding significant differences for all three tests, our results indicate that the plyometric training improved times RESULTS in the
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