PURPOSE: To examine gluteus medius strength and endurance in relation to lower limb stability, targeting and agility. METHODS: 57 participants performed isometric and dynamic gluteus medius strength and endurance tests of both lower limbs. Lower limb dominance was determined using the Waterloo Footedness Questionnaire-Revised (WFQ-R). Strength and endurance of gluteus medius were compared to single-leg performance of a stork stand, a lateral foot targeting task and a hopping test of agility. RESULTS: Body mass normalized isometric gluteus medius strength was found to be weakly and inversely correlated to agility score for both dominant limbs (r=-0.262, p=0.026) and non-dominant limbs (r=-0.335, p=0.006) with a lower agility score indicating better agility performance. For non-dominant limbs only, body mass normalized isometric gluteus medius strength correlated negatively to targeting speed (r=-0.229, p=0.045) and isometric gluteus medius endurance measured as percentage drop in strength over time correlated weakly and positively to the amount of body sway demonstrated during a single-leg stork stand task (r=0.253, p=0.030). CONCLUSION: Gluteus medius strength may be weakly related to improved agility performance while gluteus medius endurance may weakly relate to improved single-leg static balance performance. It is likely that other factors such as neuromuscular training have a much larger influence on stability, targeting ability and agility than the strength and endurance of the hip abductors alone.

The number of patients electing to undergo total hip arthroplasty (THA) in the United States has been projected to double by the year 2030, with a growing number of these patients below the age of 65 years. This cohort of patients not only desires to return to pain free daily activity, but wishes to participate in recreation and sporting activities. However, many of these patients report pain, impairments, and functional limitations following THA. The number one deficit observed for patients who fail conventional post-operative rehabilitation is persistent weakness of the hip abductor muscles. In order to safely progress these patients back to their desired activity level, appropriate postoperative rehabilitation programs need to be developed. The primary objective of this dissertation was to examine the effectiveness of a hip abductor strengthening program on subjective and objective outcomes following THA. The secondary aims of this study were to document hip muscle activation and lower extremity movement patterns during functional exercises; and to compare shortterm subjective and objective clinical outcomes for subjects following THA compared to controls. Several observations were made from our results. First, the lunge, single leg squat, and step-up and over exercises may be appropriate to include in post-operative rehabilitation programs to transition THA subjects from static strengthening exercises to dynamic activities. Second, subjects at 6- and 12-weeks following THA continue to exhibit strength and functional deficits, which contributes to decreases in activity level. Third, the addition of an exercise program targeting the hip abductor muscles following THA may help to improve subjective and objective outcomes compared to conventional post-operative rehabilitation. Finally, findings from our results are summarized and we propose a model to develop patient-specific rehabilitation programs.