Functional fatigue of the hip and ankle musculature cause similar alterations in single leg stance postural control.

Isokinetic fatigue protocols have been used to determine the relative importance of lower extremity musculature to the maintenance of balance. However, these protocols are not representative of physical activity, thus the recommendations based on these findings may be inappropriate. Therefore, purpose of this investigation was to use a completely within subjects design to examine the effects of a functional ankle and hip fatigue protocol on postural control during single leg stance. All testing was completed in a health and wellness facility where 18 healthy recreationally active university students (nine female, nine male: 21.2+/-1.96 years, 72.2+/-17.8 kg, 170.4+/-10.12 cm) volunteered to participate. Testing consisted of functionally fatiguing the ankle plantar flexors and dorsiflexors as well as the hip flexors and extensors. Postural control was assessed with two pre- and post-fatigue 20s trials during single leg stance. Three measures of dynamic balance: the overall, medial/lateral, and anterior/posterior stability index were calculated using the Biodex Stability System at stability level 4. Three separate 2-way repeated measure ANOVAs indicated that fatigue of both the ankle (plantar flexors, dorsiflexors) and hip (flexors, extensors) musculature led to postural control impairments for the medial-lateral stability index (p<0.01), and anterior-posterior stability index (p<0.01). However, only ankle fatigue resulted in deficits in the overall stability index were (p<0.01). Furthermore, neither fatigue protocol impaired single leg stance postural control more than the other (p>0.05). Our results contradict previous isokinetic fatigue protocol findings, which indicate that proximal musculature fatigue results in greater postural control deficits. Copyright (c) 2009 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.