Correlational Effects Of Plyometric Training On Leg ... - CiteSeerX

Correlational Effects Of Plyometric Training On Leg Muscle Strength, Endurance And Power Characteristics Of Nigerian University Undergraduates Ademola O. Abass

Department of Human Kinetics And Health Education Faculty of Education University of Ibadan, Ibadan Nigeria. E-mail: [email protected] Phone: +2348055436276

Abstract This study focused on the relationship among strength, endurance and power performance characteristics of untrained university undergraduates following three different modes of plyometric training. Participants were 40 untrained volunteer male undergraduates, randomly assigned to three experimental plyometric training groups of depth jumping, rebound jumping and horizontal jumping over a distance, and a fourth group which served as the control. The three experimental groups were made to go through a 12-week exercise programme based on plyometric training procedures. Interval training method was adopted while the progressive resistance training principle was considered to determine the duration and intensity of training. Data collected were analyzed using the mean, standard deviation and range. Relationship between variables was determined using the Pearson Product Moment Correlation Coefficient. Results show that there were no significant relationships among the groups in strength and endurance performance characteristics. Significant correlations were recorded in power performance between horizontal jumping and rebound jumping group [0.672; P= 0.033]. All other interactions among the groups on leg power were not significant. On relationship among the three variables based on pooled data across the groups, significant correlation was recorded only between muscle strength and power [0.327;P= 0.039]. Correlation between all other variables was found not to be significant. Based on the finding of the study it was concluded that plyometrics training with repeated jumps horizontally and that which involves rebound jumping on the spot, are capable of improving leg muscle power in similar ways. Moreover, the study also concluded that, plyometrics training is capable of improving leg muscle strength and power significantly. Introduction Sports science generally aims at identifying and developing performance variables essential for competitive excellence. Performance indices like muscle strength, endurance and power, play cardinal role in achieving athletic excellence. According to Guyton (1991), the final common denominator in athletic events is what the muscle 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. The leg muscles play important roles in the successful execution of skills in many games and sports. Although, apart from soccer, combat sports, running and jumping events in athletics, the direct use of legs is not common to most other sports. Most of these other sports that utilizes mainly the arms directly for skill execution, still require strength, and

International Journal of African & African American Studies Vol. IV, No. 1, Jan 2005

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endurance of the leg muscle to generate force and carry them through the stress and duration of their activity. Plyometric exercises have been used successfully over the years to elicit training responses from athletes. According to Chu, (1998) plyometrics are training techniques used by athletes in all types of sports to increase strength and explosiveness 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. It consists of a rapid stretching of a muscle (eccentric action) immediately followed by a concentric or shortening action of the same muscle and connective tissue (Baechle and Earle, 2000). 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 stored elastic energy within the muscle is used to produce more force than can be provided by a concentric action alone ( Komi, 1992; Miller, et al., 2002; Pfeiffer, 1999; Wathen, 1993). Researchers have shown that plyometric training, when used with a periodized strength-training program, can contribute to improvements in vertical jump performance, acceleration, leg strength, muscular power, increased joint awareness, and overall proprioception (Harrison and Gaffney, 2001; Hennessy and Kilty, 2001; Miller et al., 2002; Paasuke et al., 2001). The fundamental reason to train with plyometrics is to reduce the ground contact time that an athlete spends when running or jumping. This time is reduced as the athlete matures, gets stronger, and practices the skills of their game. To further enhance resistance training the athlete spends considerable time practicing the specific movement skills they wish to improve; namely, running and jumping. These two movement patterns are often thought of as genetic endowments and affected little by outside influences such as training programs. To the contrary, research has shown that virtually all athletes can positively influence their performance outcomes by using plyometric training on a regular basis.(Chu, 2004). The training modes derived for this study were based on the principle of plyometrics training. This study focused on the correlational effect of depth jumping, rebound jumping and horizontal jumping over a distance (three modes of plyometrics training) on the leg muscle strength,, endurance and power performance of untrained University males. The hypotheses tested in this study are as follows: 1. There is no significant relationship in the leg-muscle strength, endurance and power performance characteristics among the various groups under study. 2. There is no significant relationship in the posttest leg muscle strength, endurance and power performance of all subjects across the groups. 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.


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Instrument and Measures The main variables measured in this study were leg muscle strength, leg muscle endurance, and leg muscle power. Additional variables include age, height and weight of participants. Leg muscle strength 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 reported a reliability value of .86 to .90 for the instrument. Leg muscle endurance of subjects was measured using the half-squat jump test as described by Johnson and Nelson, (1986A reliability of .82 was recorded for the test. The Vertical jump (Sergeant chalk jump) test was used to measure leg muscle power. The measurement and scoring procedure adopted were those of Johnson and Nelson, (1986, who recorded a reliability of . 93 for the test. 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. The entire training programme was designed according to the recommendations of experts in plyometrics training. Data collection All the tests were administered by the researcher with the help of four research assistants who helped in recording, observing and timing the subjects as the need arose. Subjects were informed of the nature of the test and each of them signed an informed consent form before commencement of training. Training The training programme lasted for a period of 12 – weeks. Participants were trained three times a week between 3 pm and.6pm. Subjects were randomly divided into four groups of ten subjects each. Group one engaged in depth jumping as their training mode, participants in groups two and three engaged in rebound jumping and horizontal bounding with rings respectively, while the fourth group served as the control group which received no treatment. The training programme was based on the interval training principle, which comprised series of plyometrics exercise work intervals, interspersed with relief intervals with a work relief ratio of 1:3. The progressive resistance training principle was used in determining the dosage at every period of training. The intensity and duration of exercise were gradually increased every two weeks, when training was assumed to have become less challenging to the leg muscles of the subjects. The plyometrics - training modes, developed for this study are described as follows: Depth Jumping: This exercise was performed by using three wooden boxes that were 60cm in width, and 35cm, 40cm and 45cm in height. The subject was expected to climb the box and stand straight in the front edge of the box. He steps down and rebound from his jump after landing to the height of the box. He then moves quickly to the back of the box and repeats the exercise all over until the stipulated time. Rebound Jumping: - This exercise was performed near a training wall. It involved continuous jumping with the two feet leaving the ground at the same time. The subject was expected to rebound after landing from each jump. To ensure efficiency in this exercise, a


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20cm distance from the standing - reach height of the performer was marked against the wall in front of the performer. This served as the minimum height he can get to with his arms raised when he is jumping. Horizontal bounding with rings: - This exercise was performed on a marked ground of 9metres in distance. Six rings were alternately placed on each side of the marked line. The subject jogs into the start of the drill for forward momentum. After a few feet, forcefully push off with the left foot and bring the right leg forward. At same time swing left arm forward and land into the first ring, which is 3-4 feet out and to the left, with the right foot. He continue and repeat with other leg and arm into the second ring, which is now 3-4 feet up and to the right. This exercise is an exaggerated running motion focusing on foot pushoff and air time. Research Design and Methodology. The design for this research was the randomized pre- test - posttest control group design. Participants were randomly assigned to experimental and control groups after the selection, to eliminate selection bias as a threat to internal validity. The descriptive statistics of mean, standard deviation and range were used. Also Pearson Product Moment Correlation Coefficient was used to determine whether significant relationships existed among the groups on each of the variables tested in the study; and also to determine whether there was any significant correlation in the posttest strength, endurance and power performance of subject across all the groups. Variables. All variables were tested at 0.05 level of significance. Results GROUPS Depth Jumping Group

AGE [years]

Height[metres]

Weight [kg]

X ± SD

21.90±3.07

1.74±0.05

65.27± 6.48

Rebound Jumping Group

X ± SD

21.90 ± 4.82

1.76 ± 0.06

64.90 ± 3.74

Horizontal bounding with rings Group

X ± SD

24.50 ±2.01

1.70+ 0.07

64.54 ± 6.24

X ± SD

24.30 ±5.48

1.69 ± 0.07

66.42 ± 8.05

Control Group


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TTable 1: Descriptive Data on Age, Height, Weight Characteristics of Subjects. Table 1 shows the mean and standard deviation of age, height and weight of participants. The horizontal bounding with rings group was the oldest with a mean age of 24.50 + 2.01 years followed by the control group (24.30 + 5.48). The depth jumping and rebound-jumping group had the lowest age (21.90+ 3.07years and 21.90+4.82years respectively. The rebound jumping group was tallest with a mean height of 1.76+ 0.06 metres, followed by the depth-jumping group with 1.74+ 0.05 metres. The horizontal bounding with rings group had a mean height of 1.70+ 0.07 metres, while the control group had the lowest mean height of 1.69+ 0.07 metres. The control group recorded the heaviest mean weight of 66.42+8 05kg, followed by the depth -jumping group[ 65.27+6.48kg], the rebound jumping group [64.90+ 3.74kg] and the horizontal bounding with rings group [64.54+ 6.24kg] respectively. This showed that the control group was heaviest, while the horizontal bounding with rings group recorded the lowest weight. Groups

N

Mean

Depth jumping group

10

64.00

Standard Deviation 21.18

Rebound jumping group 10 55.60 19.01 Horizontal bounding with rings 10 41.00 25.95 group Control group 10 34.90 10.59 Table 2: Descriptive statistics on posttest Leg muscle strength performance of subjects Table 2 shows that the depth jumping group had the highest posttest leg muscle strength mean performance (64.21± 21.18); followed by the rebound jumping group, (55.60± 19.01); and horizontal bounding with rings group (41.00 ± 25.95),and the control group(34.90± 10.59) respectively. Groups

N

Mean

Depth jumping group

10

42.50

Standard Deviation 9.63

Rebound jumping group Horizontal bounding with rings group

10 10

38.10 43.40

13.31 14.58


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Control group 10 23.30 11.93 Table 3: Descriptive statistics on posttest Leg muscle endurance performance of subjects Results from the above table shows that horizontal bounding with rings group had the highest mean leg endurance performance (43.40±14.58), followed by depth jumping group (42.50±9.63), and rebound jumping group (38.10±13.31), while the control group (23.30±11.93), recorded the lowest performance. Groups

N

Mean

Standard Deviation 12.09 12.06 8.73

Depth jumping group 10 105.70 Rebound jumping group 10 104.10 Horizontal bounding with rings 10 110.50 group Control group 10 101.70 12.19 Table 4: Descriptive statistics on posttest leg muscle power performance of subjects Results from the above table revealed that horizontal bounding with rings group recorded the highest posttest relative leg power (110.50±8.73),followed by the depth jumping group (105.70±12.09), and the rebound jumping with rings group (104.10±12.06). The control group again recorded the least performance (101.70±12.19) in posttest leg power performance. Group scores on all variables

N

Mean

Standard Deviation 22.46 14.52

Leg strength score across all groups 10 48.88 Leg endurance score across all 10 36.83 groups Leg power score across all groups 10 105.50 11.39 Table 5: Descriptive statistics of performance on all variables across all the experimental groups

The above table shows that the mean leg strength performances of subjects across the experimental groups is 48.88±22.44, while their mean leg muscle endurance performance is 38.83±14.52, and mean relative power performance is 105.50±11.39.

depth jumping (post-teststrength)

Depth jumping (post-teststrength)

Horizontal jumping (posttest strength)

Rebound jumping (posttest strength)

Control gp(posttest strength)

Pearson Correlation

1.000

.69

.290

-346

Sig. (2tailed) N

.

.851

.416

.327

10

10

10

10



Rebound jumping(posttest strength)

48

Pearson Correlation

.069

1.000

.096

-307

Sig. (2tailed) N Pearson Correlation

.851

.

.791

.388

10 .290

10 .096

10 1.000

10 -201

.

.577

10 -.201

10 1.000

.577

.

10

10

Sig. (2.416 .791 tailed) N 10 10 Control (posttest Pearson -.346 -.307 strength) Correlation Sig. (2.327 .388 tailed) N 10 10 *Correlation is significant at the 0.05 level (2-tailed)

Table 6: Correlation coefficients matrix of muscle strength performance among all the groups The above correlation coefficient matrix table reveals that there was no significant relationship in leg muscle strength of subjects in the three-plyometric groups and the control group. This shows that there was no significant association in the muscle strength training effects generated by the three-plyometric training modes used in this study following 12weeks of training


Horizontal jumping(posttest strength)

Rebound jumping(posttest strength)



Rebound jumping (posttest strength)


Pearson Correlation

1.000

-.504

.066

.041


.

.137

.857

.910

10 -.504

10 1.000

10 -.295

10 .083


.137

.

.409

.820

10 .066

10 .-295

10 1.000

10 -.626

Sig. (2-

.857

.409

.

.053



tailed) N Pearson Correlation

10 .041

49

10 -.083

10 -.626

10 1.000

Sig. (2.910 .820 .53 . tailed) N 10 10 10 10 *Correlation is significant at the 0.05 level (2-tailed) Table 7: Correlation coefficients matrix of muscle strength performance among all the groups The correlation matrix table above also reveals no significant relationship in leg muscle endurance of subjects among the three plyometric groups and the control group. This shows that there was no significant correlation in the training effects elicited by the three plyometric training modes following 12 weeks of training.

depth jumping (post-teststrength) Horizontal jumping (posttest relative power) Rebound jumping(po sttest relative power) Control gp(posttest relative power)

Horizontal jumping (posttest strength) .198

Rebound jumping (posttest strength) .363

Control group (posttest strength) .098

Sig. (2-tailed) . N 10 Pearson .198 Correlation

.583 10 1.000

.302 10 .672

.788 10 -.350

Sig. (2-tailed) .583 N 10 Pearson .363 Correlation

. 10 .672

*.033 10 1.000

.321 10 .074

Sig. (2-tailed) .302 N 10 Pearson .098 Correlation

*.033 10 -.350

. 10 .074

.840 10 1.000

Sig. (2-tailed) .788

.321

.840

.

Pearson Correlation

Depth jumping (post-teststrength) 1.000


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N 10 10 10 10 *Correlation is significant at the 0.05 level (2-tailed) Table 8: Correlation matrix of muscle performance among all the plyometric and control groups Table 8 shows that there was significant relationship in leg muscle power (0.672; P=0.033) between subjects in the horizontal bounding with rings and rebound jumping groups subjects. However, no significant correlation was recorded in all other inter-group comparisms on leg-muscle power. This shows that only horizontal bounding with rings and rebound jumping plyometric training modes have similar capacity to develop leg muscle power out of the three modes used in the study.

Strength score across all the groups Endurance score across all the groups Absolute power score across all the groups Relative power score across all groups

Strength score across all the groups 1.000

Endurance score across all the groups .189

Relative power score across all the groups .327

Sig. (2-tailed) N Pearson Correlation

. 40 .189

.243 40 1.000

*.039 40 .160


.243 40 .461

. 40 .371

.324 40 .517


.003 40 .327

.018 40 .160

.001 40 1.000

Sig. (2-tailed) N

*.039 40

.324 40

. 40

Pearson Correlation

correlation is significant at the 0.05 level (2-tailed) Table 9: Correlation matrix of strength, endurance and power performance across all the groups following plyometric training Table 9 presents the relationship that existed in strength, endurance and power performance of subject across all the groups. Results shows there was significant relationship only between leg muscle strength and power (0.327;P = 0.039). correlations between all other variables were found not to be significant. This shows that there was relationship only in the strength and power effects generated in the athletes following plyometric training. Discussion


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Results of this study revealed a non-significant correlation among the plyometric and control groups used in this study on strength and endurance performance characteristics of subjects. This shows that there were no significant interactions in the muscle strength and endurance training effect generated by the various plyometric training modes used in the study. A significant relationship was however recorded in leg power performance of horizontal jumping and rebound jumping group. This result may not come as a surprise because the real essence of plyometric training is not development of strength but explosive power. According to Gambetta (2003) plyometric training is specific work for the enhancement of power. It deals with the rate and not magnitude of the stretch to determine the utilization of elastic energy and the transfer of chemical energy into mechanical work. Also in determining whether relationships exists among the variables under study based on performance across all the groups, a significant relationship was recorded only between muscle strength and power (0.327; 0.039 2 tail sig.). This result only confirms the fact that strength has a significant contribution in power performance. Power performance has been found to be a product of efficient strength and speed development. Conclusion Based on the findings of this study, it was concluded that only the horizontal bounding with rings and rebound jumping training used in this study have similar capacity to develop leg power attributes. This implies that these two plyometrics training can be used interchangeably in developing leg muscle power in various sports. Moreover, the plyometric training techniques used in this study only exhibited relationship in leg muscle power and leg muscle strength attributes of athletes. Based on the findings of this study, it is recommended that plyometric mode should be included in all trainings that involve the development of explosive power and strength of the leg muscles either for recreation, competition, or rehabilitation purposes. REFERENCES Baechle, T.R. and Earle, R.W. (2000) Essentials of strength training and conditioning. 2nd edition.Champaign, IL: National Strength and Conditioning Association. Brown,M.E,Garbutt, G Reilly, T.Linge, K & Troup, J.D.G (1988). The effects of gravity inversion on exercise induced spinal loading. Ergonomics, 31,(1631-1637). Brzyckim M (1986), Plyometrics : A giant step backwards. Athletics Journal,72, (86), 22-23. Chu, D.A. (2004).Plyometric Training for Youth. http//www.donaldchu.com Guyton, A.C. (1991). Textbook of medical physiology (8th ed.) Philadelphia:W.B.Saunders co. Harrison, A.J. and Gaffney, S. (2001) Motor development and gender effects on stretch-shortening cycle performance. Journal of Science and Medicine in Sport 4, 406-415. Hennessy, L. and Kilty, J. (2001) Relationship of the stretch-shortening cycle to spring performance in trained female athletes. Journal of Strength and Conditioning Research 15, 326-331.


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