Comparative Effect of Three Modes of Plyometric Training on Leg Muscle Strength of University Male Students

This study determined the comparative effect of three modes of Plyometrics training [depth jumping, rebound jumping and horizontal jumping] on leg muscle strength of untrained University male students. Participants were forty untrained male University students within the age range of 18-27 years. The randomized pretest-posttest control group design was adopted. Subjects were randomly assigned to control group, and three experimental groups based on the types of plyometrics training adopted for the study. The training programme consisted of twelve weeks of interval training administered three times a week. Data collected were analyzed using the mean score, standard deviation and range. Analysis of Covariance [ANCOVA] was used to test for significant differences in the posttest measures among the treatment and control groups using the pretest score variation as covariates. Scheffe post hoc analysis was used to determine which of the means were significantly different. All hypotheses for the study were tested at 0.05 critical level. Findings revealed that only the depth jumping and rebound jumping training significantly altered leg muscle strength of subjects (P<0.05). Based on the findings, it was concluded that plyometrics exercises with depth jumping and rebound jumping characteristics are best used in developing muscle strength of the lower extremities. Introduction Sports science generally aims at identifying and developing performance variables essential for competitive excellence. In addition to other indices like muscle endurance and power, muscle strength plays a cardinal role in achieving athletic excellence. The final common denominator in athletic events is what the muscles can do for you what strength they can give when it is needed, what power they can achieve in the performance of work and how long they can continue in their activity [Guyton (1991),. The leg muscles play vital roles in the successful execution of skills in many games and sports. Although, apart from soccer, combat sports, running and jumping events in athletics, direct use of the leg is not common to most other sports. However, most of these other sports, which depend mainly on the arm and other parts of the body, still require strength, and endurance of the leg muscle to generate force and carry them through the stress and duration of their activity. Muscular strength is the maximal force or toque a muscle or muscle group can generate at a specified or determined velocity. It is also the ability of a muscle or a group of muscles to sustain contraction in one maximum repetition.[ Komi,,1992; Hockey,1993). Muscle strength is considered to be a basic component in the performance of physical skills and in almost all competitive activities the performer with the greater amount of strength has the advantage. All sports require a certain amount of Comparative Effect of Three Modes of Plyometric Training on Leg Muscle Strength of University Male Students 578 strength, but strength becomes a priority in sports where heavy weights such as the body must be lifted, carried or thrown (Sharkey, 1986). Plyometric exercises have been used successfully over the years to elicit training responses from athletes. Plyometrics training is almost exclusively applied to extensor Muscle of the legs, and consists of a vigorous lengthening of the active extensor muscles (eccentric contraction) immediately followed by a maximal concentric contraction. They are most frequently used as a means of increasing speed and anaerobic power output in sprinters and jumpers, but the techniques may also be of value to other types of sportsmen (Watson, 1993; Wausen, 1990). Sharkey (1986) described plyometric exercises as explosive callisthenic-like exercises which involve the conditioning of the neuromuscular system to permit faster and more powerful changes of direction such as moving from up and down in jumping or switching leg positions as in running. The training modes adopted for this study were based on the principle of plyometrics training. Therefore, this study focused on the relative effect of depth jumping, rebound jumping and horizontal jumping over a distance (three modes of plyometrics training) on the leg muscle strength development of untrained University males. It was hypothesized that there no significant differences exist in the pretest posttest leg muscle strength of subject following a twelve-week depth jumping, rebound jumping and horizontal jumping over a distance plyometrics programme. Method and Procedures Participants Forty apparently healthy untrained male undergraduates of the University of Ibadan, Nigeria, participated in the study. Subjects were volunteers, certified medically and physically fit to take part in the training programme. They were randomly divided into four groups of 10 participants each. Three of these groups served as the experimental groups that participated in the depth jumping, rebound jumping and horizontal jumping exercises, while the fourth was the control group. Instrument and Measures The main variable measured in this study was the leg muscle strength. Additional variables include age, height and weight of participants. Leg muscle strength of participants was measured using the back and leg dynamometer. The test protocol for using the instrument was followed as described by Johnson and Nelson, (1986) They also reported a reliability value of .86 to .90 for the instrument. The stadiometre and its weighing scale were used to measure height and weight; three locally manufactured boxes, each of which were, 35cm, 40cm, and 45cm in height were used for depth jumping training, a training wall was used for rebound jumping training; a marked ground of nine metres in length with 6 rings placed alternately on the ground were used for horizontal jumping training; while stopwatches and measuring tape were used to measure time and distance respectively.