Low strength is related to diminished ground reaction forces and walking performance in older women

The purpose of this study was to determine how lower-limb strength in older women affected gait speed, supportive forces, spatial, and temporal aspects of walking gait. Twenty-four women between 65 and 80 yr performed maximal voluntary isometric contractions for the knee extensors (KE), knee flexors (KF), ankle plantarflexors (PF) and ankle dorsiflexors (DF) and were separated into low strength and normal strength groups using a KE torque threshold of 1.5 Nm kg(-1). They walked at both a standard speed of 0.8 m s(-1) and at a self-selected maximal speed on an instrumented treadmill that recorded vertical ground reaction forces (vGRF) and spatiotemporal gait measures. Older women with low strength had 30% lower KE maximal torque, 36% lower PF maximal torque, 34% lower KE rate of torque development (RTD) and 30% lower KF RTD. Low strength women demonstrated slower maximal walking speeds (1.26 +/- 0.20 m s(-1) vs. 1.56 +/- 0.20 m s(-1)), lower vGRF during weight acceptance (1.15 +/- 0.10 BW vs. 1.27 +/- 0.13 BW), lower weight acceptance rates (11.3 +/- 0.5 BW s(-1) 17.0 +/- 5.5 BW s(-1)), slower stride rates, shorter stride lengths, and longer foot-ground and double-limb support times (all P < 0.05). Maximal gait speed was strongly correlated to peak vGRF and rate (r = 0.60-0.85, P < 0.01) and moderately related to lower-limb strength (r = 0.42-0.60, P < 0.05). In older women with low strength, diminished peak vGRFs were associated with slower walking speeds putting them at risk for mobility limitation, disability, poor health, and loss of independence. (C) 2011 Elsevier B.V. All rights reserved.