The Effects of Concentric, Eccentric and Isometric Training Methods on Leg Extensor Strength PDF Download

Author: Richard R. Danielson
Publisher:
ISBN:
Category : Leg
Languages : en
Pages : 0

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Book Description
A study was undertaken in order to compare the relative efficacy of concentric, eccentric and isometric training on strength of leg extensor muscles. Subproblems investigated were the rate of training for each of the 3 groups, the establishment of concentric, eccentric and isometric strengths of leg extensors and the formulation of equations for predicting any one strength from one of the other two. Three groups of 10 University of Alberta freshmen participated in and completed a training and testing program over a period of 9 weeks, 7 weeks serving as training sessions. Four tests were given throughout the course of the experiment; concentric, eccentric and isometric strength being measured during each test. During the first 3 train ing sessions, all subjects executed 6 contractions of the type assigned to their respective groups and by the eighteenth training session, they executed 18 training con tractions per session. Training occurred on an average of 3 times weekly for all subjects; usually Monday, Wednesday and Friday. Subject data was subjected to analyses of variance and the leg strength data was subjected to 3 analyses of variance; one for concentric strength over the 4 test periods, one for eccentric strength and one for isometric strength. The analyses for concentric and eccentric strength were conducted on average force (lbs.) of 2 contractions at knee angles of 80 to 140 degrees inclusive. The analysis for isometric strength was conducted on average force at knee angles of 70, 110 and 150 degrees respectively. Each analysis was of a split-plot design with 2 factors between and 2 factors within subjects. Sheffe's test for multiple comparisons was applied to all significant interaction mean squares. Results indicated that the 3 training groups did not differ significantly in mean age, height, initial weight, final weight, upper leg length, lower leg length, initial leg girth or final leg girth. Subjects increased signifi cantly in weight. Both the concentric and eccentric training groups increased significantly in leg girth (cm.) over the course of the experiment, while the isometric group did not increase significantly. Both concentric and isometric strength could be described more advantageously by a quadratic than by a linear equation linking average force with knee angle. Eccentric strength could be described equally well by either a linear or quadratic equation. Average eccentric strength over angles of 60 to 150 degrees inclusive was found to be 87.07% greater than average concentric strength over the same 10 angles. Average isometric strength over the angles of 70, 110 and 150 degrees was found to be 92.09% greater than average concentric strength and 0.16% less than average eccentric strength over the same 3 angles. Eccentric and concentric strength at angles 80 to 140 degrees inclusive, as well as eccentric and isometric strength at a knee angle of 110 degrees were found to be essentially unrelated as indicated by their small amount of common variance (less than 20%). Concentric and isometric strength at 110 degrees were better related (45.14% common variance) indicating that prediction from one to the other at that angle would be possible. Results of the concentric analysis showed that the eccentric and isometric training groups both increased sig nificantly at the .05 level in mean concentric strength. The concentric training group showed a decrease in performance from test 3 to test 4 and did not increase significantly over the experiment. The isometric training group was found to produce the optimum rate of mean strength increase over the first 5 weeks of training after which the eccentric training group proved to be as effective as that group. All groups increased significantly in mean eccentric strength over the 7 weeks of training. Although the mean strength for the concentric training group was found to be significantly greater than the mean for the other 2 over the first 3 tests, it was seen by inspection that the linear slopes of the concentric and isometric training groups were similar and greater indicating that these 2 methods of training provided faster rates of eccentric strength increase than did isometric training. The concentric and isometric training groups increased significantly in mean isometric strength over the 4 test periods. The eccentric group did not increase significantly in mean isometric strength, but did not differ significantly from the other 2 training groups with respect to rate of strength increase. It was concluded that all 3 training methods are equally effective in increasing isometric strength. In all 3 methods of measuring strength, it was seen that the greater knee angles showed training effects more than the lesser knee angles. The general conclusion of the study was that isometric training proved to be the most advantageous in improving strength measured concentrically, eccentrically and isometrically. Specificity of training effects were not seen in the present study.