Sex dependent differences in biceps brachii muscle size, overlying subcutaneous fat thickness and corticospinal excitability

Olarogba, Olalekan B. (2022) Sex dependent differences in biceps brachii muscle size, overlying subcutaneous fat thickness and corticospinal excitability. Masters thesis, Memorial University of Newfoundland.

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Indirect measurement of subcutaneous fat thickness using skinfold measurement has been used as the most common method of investigating fat thickness in humans. Likewise, studies that have reported on the muscle size mostly involved cadaver studies. From this research, muscle size and subcutaneous fat thickness were measured using B-mode ultrasound and the effect of these factors on corticospinal excitability were determined. Many studies have investigated the role of the corticospinal tract in the development of voluntary force. However, the effect of muscle size and fat thickness on corticospinal excitability has not been examined. The current study was designed to assess corticospinal excitability of the biceps brachii using a transcranial magnetic stimulation (TMS) protocol and assess muscle and fat thickness via B-mode ultrasound to determine the impact of muscle and fat thickness has on corticospinal excitability and whether or not this impact was sex-dependent. The maximum stimulator output required to achieved active motor threshold was higher in female than male. Motor evoked potential (MEP) amplitudes from the biceps increased significantly (p < .001) and similarly (p = .365) for both men and women. For men there was a significant (p < .05, r = 0.591) positive relationship between muscle size and MEP amplitude, whereas for women there was a significant (p < .05, r = -0.525) negative relationship between MEP amplitude and skinfold thickness. Collectively, the data suggest that the amount of muscle size and subcutaneous fat thickness affects CSE, and these findings are sex- dependent.

Item Type: Thesis (Masters)
Item ID: 15843
Additional Information: Includes bibliographical references
Keywords: ultrasound, transcranial magnetic stimulation, motor evoked potentials
Department(s): Human Kinetics and Recreation, School of > Kinesiology
Date: December 2022
Date Type: Submission
Digital Object Identifier (DOI):
Library of Congress Subject Heading: Muscles--Physiology; Pyramidal tract--Physiology; Excitation (Physiology); Magnetic brain stimulation

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