Electronic Theses and Dissertations

Date of Award

2018

Document Type

Dissertation

Degree Name

M.S.E.S. in Exercise Science

Department

Health, Exercise Science, and Recreation Management

First Advisor

Xin Ye

Second Advisor

Ling Xin

Third Advisor

Mark Loftin

Abstract

The aim of this study was to examine the time to task failure for two different fatiguing tasks (force vs. Position task) on elbow flexion exercise, in order to explore potential mechanisms of muscle fatigue. Twenty healthy and recreationally active individuals (10 men and 10 women) participated in this 3-visit investigation. At least 48 hours after the first visit as the familiarization, the subject returned for one of the experimental visits (order randomized). During the force task visit, the subject performed maximal voluntary contractions (mvcs), several submaximal trapezoid isometric contractions with different intensities (40% and 70% of mvc), and followed by ample rest and the time to failure task. For the position task visit, similar tests were conducted, but only with the position task setup. A minimum of 48 hours of rest was provided between visits. A paired samples t-test was used to compare the maximal force values. A two-way repeated measures (sex [men vs. Women] ã— condition [force task vs. Position task]) analysis of variance (anova) was used to examine the time to task failure between two tasks. In addition, separate three-way mixed factorial (sex ã— condition ã— time) anovas and three-way mixed factorial (sex ã— condition ã— intensity) anovas were used to examine emg parameters during the isometric fatiguing contractions and submaximal trapezoid contractions, respectively. There was no significant difference in time to task failure between two tasks, however, the time to task failure for men was significantly longer than women. In addition, the normalized emg amplitude values of biceps brachii and triceps brachii for women were significantly higher than for men during the fatiguing contractions, and the normalized emg median frequency value of triceps brachii for force task was significantly higher than the position task. In conclusion, during the fatiguing contractions, the muscle activities of women's angonist and antagonist increased quicker than those of men's, which led to a briefer time to task failure for women. Although no difference in time to task failure was found between tasks, motor control strategies for the antagonist muscle seem to be different.

Included in

Kinesiology Commons

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