Date of Award

1993

Document Type

Scholarly Project

Degree Name

Master of Physical Therapy (MPT)

Department

Physical Therapy

First Advisor

Henry C. Wessman

Keywords

Hypertrophy; Muscles -- physiology

Abstract

This study was undertaken to determine whether concentric or eccentric muscle action was more likely to induce muscle hypertrophy when exposed to a prolonged heavy resistance exercise program. Fifteen males and 14 females who were not currently or recently involved in a heavy resistance training program for the lower extremities were selected for the study. One group (n = 10) exercised in a concentric fashion, another group (n = 9) exercised in an eccentric fashion, and a third group (n = 10) served as a control group, performing no resistive exercise. The exercising subjects performed three sets of 10 repetitions of resistive knee flexion and extension exercise at 60 degrees/sec, three times per week for 15 weeks at 80% to 100% of their maximal concentric work output on an isokinetic exercise device. Subjects were allowed to increase their intensity of effort as the program progressed to provide continual overload to the exercising muscles to encourage maximal hypertrophy. Isokinetic testing was performed with all subjects at the beginning and at the end of the study, with additional testing of the exercise groups every four weeks to aid in determining effort goals for exercise. Muscle cross-sectional area of the midthigh was measured at the beginning and at the conclusion of the study by computed tomography. Analysis of percentage of increase in muscle cross-sectional area showed that the mean increase in the eccentric, concentric, and control groups was 5.0%, 4.6%, and -1.8%, respectively. A significant statistical difference in hypertrophic response was demonstrated by the exercise groups in comparison to the control group; however, no significant difference in hypertrophy was exhibited in the comparison of the concentric and eccentric groups' results. These results suggest that neither concentric nor eccentric heavy resistance exercise is more likely to promote hypertrophy than the other. However, the results do support the theory that suggests heavy resistance training is more likely to produce increased muscle mass than activity lacking such resistance.

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