Muscle weakness is related to slip-initiated falls among community-dwelling older adults

The purposes of this study were (1) to investigate the relationship between muscle weakness and slip related falls among community-dwelling older adults, and (2) to determine optimal cut-off values with respect to the knee strength capacity which can be used to identify individuals at high risk of falls. Thirtysix healthy older adults participated in this study. Their muscle strength (torque) was assessed at the right knee under maximum voluntary isometric (flexion and extension) contractions. They were then moved to a special treadmill. After walking regularly five times on the treadmill, they experienced an identical and unannounced slip during walking on the treadmill with the protection of a safety harness. This treadmill could be considered a standardized platform, inducing an unexpected slip. Accuracy of predicting slip outcome (fall vs. recovery) was examined for both strength measurements (i.e., the strength capacity of knee extensor and flexor) using univariate logistic regressions. The optimal cutoff values for the two strength measurements were determined by the receiver operating characteristic analysis. Results showed that fallers displayed significantly lower knee strength capacities compared to their recovery counterpart (1.10 vs. 1.44 Nm/kg, p < 0.01, effect size Cohen's d=0.95 for extensor; 0.93 vs. 1.13 Nm/kg, p < 0.05, d=0.69 for flexor). Such results suggested that muscle weakness contributes to falls initiated by a slip during gait. Our findings could provide guidance to identify individuals at increased risk of falling using the derived optimal cutoff values of knee strength capacity among older adults. (C) 2015 Elsevier Ltd. All rights reserved.