Date of Award

5-2016

Document Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department

Kinesiology

First Advisor

Jeffrey Bauer, Ph.D.

Second Advisor

Peter McGinnis, Ph.D.

Third Advisor

Larissa True, Ph.D.

Abstract

The purpose of this study was to measure the choice reaction time and myoelectric activity of the right and left rectus abdominus, and right and left external obliques required to initiate movement in response to a visual stimulus that signaled performance of four different closecombat movements (left or right cross and left or right dodge). Reaction time and myoelectric activity were then compared with performing the movements in response to the visual stimulus while wearing a weighted vest that simulated wearing tactical body armor. Myoelectric activity was measured as the average root mean square (RMS) of the surface electromyography (sEMG) values. The hypotheses were that average time to react to the visual stimulus for each movement and average myoelectric activity to initiate the movement would be greater under the weighted vest condition. The participants were 10 active martial arts/boxing performers from different disciplines with a minimum one year experience in their discipline. During two separate sessions, the participants completed eight warm-up trials and 24 measured trials, with the first four trials deleted. The stimuli were activated in a random order with foreperiods ranging from 10 to 20 seconds between trials. The sessions were randomly chosen to be either loaded or unloaded conditions. Surface EMG electrodes detected the myoelectric activity of the right and left rectus abdominus, and right and left external oblique muscles. The electrodes pre-amplified the myoelectric signals by a factor of 35. The sEMG signals of the four muscles were treated with a 20 Hz low cut/high pass filter, amplified by a factor of 20,000, and the RMS of the filtered signals were derived using an 11.75 ms time window. The analog RMS sEMG was sampled at 1020 Hz and converted to digital form. The reaction time for each movement was determined from the initiation of the stimulus to the point at which myoelectric activity iv reached the threshold of 0.5 volts. A two-tailed paired samples t-test was run to determine differences between the average reaction time and average RMS sEMG for each core muscle during each movement for the unweighted and weighted conditions. A one-way ANOVA with repeated measures was run to determine significant differences in average reaction time and average total muscle activity between the unweighted and weighted conditions for the group. Alpha was set at 0.05. Significant differences were found between the unweighted and weighted conditions for reaction time while performing the left dodge, right cross, and right dodge with slight significance for the left cross (p = 0.047, p = 0.014, p = 0.002, and p = 0.059, respectively). Further, group average reaction time was significantly greater in the weighted condition (p = 0.001). No significant differences were found in initial muscle activity between the conditions. These results support the first hypothesis that mean reaction time would significantly increase when performing close-quarters combat movements in response to a visual stimulus while wearing a loaded vest. Combatives instructors, specifically military and law enforcement, can use this information as a means to further protect the armed forces by training them in the protective gear that they will be wearing out in the field. This will hopefully acclimatize the armed forces to a point where performance will not hinder to complete missions in hostile environments.

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