Differences in Lower Limb Muscle Activation and Variability Across Walking Speeds by Age and Fall Risk

This study aimed to determine the differences in lower limb muscle activation and variability at preferred, slow, and fast walking speeds according to age and fall risk. We divided 301 participants into groups based on age (young older: 70–79 years vs. old older: 80–90 years) and fall risk (fall risk vs. non-fall risk). We measured muscle activation and its coefficients of variation (CV) for the rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and medial gastrocnemius muscle (GCM) at speeds 20% slower, 20% faster, and 40% faster than the preferred speed (PS). When compared by age, older adults exhibited greater changes in RF and GCM activities, versus young older adults; however, the CV was not significantly different. Fall risk older adults had significantly lower GCM activity and higher CVs of RF, BF, TA, and GCM in PS. With changes in gait speed, older adults at risk of falling had significantly increased CVs of RF, BF, and GCM. Our findings provide new evidence that variability rather than muscle activity increases with walking speed in older adults at risk of falls, highlighting the importance of decreasing muscle activity variability in preventing fall risk.