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The effects of isometric strength training of the biceps brachii on electromyography, mechanomyography, and muscle strength
The purpose of the present investigation was to examine the mechanomyographic (MMG) and electromyographic (EMG) responses of the biceps brachii during incremental isometric muscle actions at forearm flexion angles of 30, 60, and 90% before and after eight weeks of isometric strength training. Seventeen adult females were randomly assigned to a control (CTL; n = 7) or training (TRN; n = 10) group. The training group performed eight weeks of isometric strength training of the non-dominant biceps brachii on a Cybex II Dynamometer at a joint angle where the Cybex lever arm was positioned 60 degrees above the horizontal plane. Training was conducted three times per week and each training session consisted of isometric muscle actions equal to 80 percent of maximal voluntary contraction (%MVC). The CTL and TRN groups were re-tested at four and eight weeks after the initial strength test. During each strength test, maximal torque (TQ), flexed arm circumference, EMG, and MMG measurements were recorded. The results indicated that following eight weeks of isometric training, there was a significant increase in forearm flexion strength and flexed arm circumference. There was, however, no change in the EMG or MMG amplitude following the training. These findings suggested that the increased strength may have been due to factors associated with muscle hypertrophy and independent of neural adaptations in the biceps brachii. It is possible, however, that there were changes in maximal activation of other forearm flexor muscles. With regard to the MMG findings, it is possible that there were counteractive influences of muscle hypertrophy which ultimately resulted in no training-induced change in the MMG amplitude. Furthermore, the increased strength may have been due to a decrease in antagonist co-contraction, thereby, resulting in no measurable change in the EMG and MMG signals. Future investigations should examine the influence of muscle hypertrophy and antagonist co-contraction on the EMG and MMG signals. ^
Health Sciences, Rehabilitation and Therapy|Biology, Animal Physiology
Ebersole, Kyle Thomas, "The effects of isometric strength training of the biceps brachii on electromyography, mechanomyography, and muscle strength" (2000). ETD collection for University of Nebraska - Lincoln. AAI9958392.