Doctoral Dissertations

Date of Award

12-1994

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Education

Major Professor

Wendell Liemohn

Committee Members

David Bassett, Craig Wrisberg, Thomas Namey, Ed Howley, Mary Sue Younger

Abstract

The purpose of this investigation was to examine the effects of submaximal eccentric isokinetic exercise on indicators of muscle damage, and to determine the optimal submaximal percentage at which eccentric isokinetic training should be performed to achieve strength and power gains in the quadriceps and hamstring muscles. The study was conducted in two parts. In Part I, 30 untrained subjects completed three sets of 15 eccentric contractions with the quadriceps and hamstrings using a Biodex isokinetic dynamometer. Subjects exercised at an intensity of 60%, 80% or 100% of their maximal eccentric peak torque, at a velocity of 60%deg;/sec. Muscle soreness and other indicators of muscle damage including range of motion, maximal voluntary isometric strength and serum creatine kinase (CK) levels were measured before and 24, 48 and 72 hours after the exercise bout. The maximal exercise group experienced significant soreness in both muscle groups relative to the two submaximal groups at 48 and 72 hours post-exercise. In addition, decreased hamstring range of motion, decreased isometric strength in both muscle groups and increased serum CK levels were seen in the 100% group, but similar changes were not evident in either of the submaximal groups. No significant difference was found between the soreness response of the two muscle groups. In Part II, 30 untrained volunteers underwent eight weeks of eccentric isokinetic training of the quadriceps and hamstrings at 60%, 80% or 100% of their maximal eccentric peak torque. Subjects performed three sets of 15 repetitions, three days per week, at a speed of 60°/sec. Ten subjects served as a control group and did not train. Eccentric peak torque at 30, 60, 90 and 120°/sec, concentric peak torque and average concentric power at 60, 180, 300 and 450°/sec, and a single leg hop for distance were measured before and after the training period. Results showed that the eccentric peak torque of both muscle groups increased significantly in all training groups when tested at 60°/sec and 30°/sec, but the greatest improvements were seen in the 80% group. In the quadriceps, similar torque gains also occurred at the test speeds of 90°/sec and 120°/sec; however, only the 80% and 100% groups demonstrated carryover in eccentric hamstring torque gains to the higher velocities. The training effects did appear to be specific to the contraction mode. Concentric peak torque did not change in the 60% and 100% groups at any tested speed and only increased in the 80% group at the 60°/sec velocity. No significant increase in average power was seen in the quadriceps. The average power of the hamstrings increased in both the 80% and 100% groups, but not in the 60% group. No improvement in the single leg hop for distance occurred in any of the three training groups. The results of this study indicate that eccentric isokinetic exercise training performed at 80% of maximal effort appears to be optimal for producing strength and power gains in the quadriceps and hamstrings while limiting the degree of muscle soreness and damage experienced after exercise.

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