Control of balance differs after knee or ankle fatigue in older women

Objective: To examine the effects of acute isokinetic knee or ankle fatigue on control of static and dynamic balance in older women. Design: Pretest and posttest. Setting: University research laboratory. Participants: Eighteen healthy, community-dwelling older women (age, 77 +/- 6y) with no history of falling. Interventions: Measurements of static and dynamic balance control before and after isokinetically fatiguing the ankle plantar- and dorsiflexors or knee extensors and flexors in separate sessions. Main Outcome Measures: Performance on 3 clinical assessments of control of balance: modified Functional Reach Test (mFRT), Lower-Extremity Reach Test (LERT), and Single-Limb Stance Time Test (SLSTT). Results: Balance declined in the mFRT after fatigue to each joint, with no significant difference in the magnitude of change between joints. Control of balance during the LERT decreased significantly only after knee fatigue, and control of balance during the SLSTT was significantly reduced only after ankle fatigue. Conclusions: Balance performance after acute isokinetic muscular fatigue to the knee or ankle is specific to the muscle groups fatigued and the balance tests used.