Date of Award

2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

Abstract

Context. Researchers have suggested a weak or dysfunctional gluteus medius (GM) has been linked to a number of lower extremity injuries. Identifying an appropriate intervention to prevent or correct GM deficits and determine associated outcomes has become a subject of increased interest. Objective To determine if GM training changes lower extremity muscle activation during a dynamic task. Design. Controlled laboratory study. Setting. Biomechanics research laboratory. Participants. Eighteen healthy, physically active participants (7 men, 11 women; age=21.2±2.01yrs; height=168.39±8.92cm; mass=77.76±16.39kg) volunteered for the study. Each participant served as their own control. Intervention(s). Muscle activation of 5 trunk muscles were measured bilaterally before and after the protocol during a single-leg drop landing (45cm). All of the participants completed a six week GM training protocol. Main outcome measure(s). Peak and mean muscle activation was measured 400ms pre-and post-landing (pre-mean, pre-peak, post-mean, post-peak). Muscle activation data was normalized using maximal voluntary contractions. Results. No significant differences were observed during the control period. Decreased muscle activation was observed in the non-dominant GM [pre-mean ( F 1,17 =14.301, P =.001), pre-peak ( F 1,17 =9.490, P =.007), post-mean ( F 1,17 =5.373, P =.033), and post-peak ( F 1,17 =4.678, P =.045)]. Increased biceps femoris (BF) mean muscle activation was observed on the dominant leg pre-landing ( F 1,17 =4.752, P =.044). Conclusions. Six weeks of GM training was enough time to observe improved neuromuscular efficiency of the GM. Increased BF muscle activation prior to landing suggests participants had an increased feedforward response in preparation for landing following training. Therefore, the combination of improved neuromuscular efficiency and a greater feedforward response suggest pelvic stabilization may be improved during a single-leg drop landing as a result of six weeks of GM training. This study suggests clinicians should incorporate bilateral GM exercises to improve lower extremity neuromuscular efficiency and feedforward responses which may improve pelvic stabilization. Key words. Electromyography, lower extremity injury, rehabilitation, neuromuscular efficiency, single-leg drop landing.

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