Regional neuromuscular regulation within rectus femoris muscle following three-month limb-loaded walking in older adults

Limb-loaded walking using ankle weights has been widely applied to increase exercise intensity in older adults. Examining changes in the activation pattern between proximal (RFP) and distal (RFD) regions of the rectus femoris (RF) muscle is key to clarifying gait deficits in older adults. The aim of this study was to determine regional neuromuscular regulation within the RF muscle following three-month limb-loaded walking in older adults. The study participants were 22 healthy older adults (69 ​± ​6.3 years) who walked at least 160 ​min per month. Surface electromyography (EMG) and motion capture were used to measure the neuromuscular activities of RFP and RFD and generate kinematic data on the left lower extremity on walking for 240 ​s at the preferred gait speed on a treadmill at pre- and post-intervention, respectively. Averaged rectified values (ARV) of RFP and RFD were normalized by maximum values of ARV during a gait cycle within ten consecutive gait cycles. Normalized ARV of RFP was greater than RFD at 30%–40% and 70%–90% of the gait cycle and hip joint flexion at 0%–100%, and the walking speed and swing timing at post-were greater than at pre-intervention (p ​< ​0.05). No significant differences were noted in the RFP to RFD activity ratio (RFP/RFD ratio) between pre- and post-intervention, and there was no correlation between the RFP activity level and hip flexion angle in the swing phase (p > 0.05). The activity of RFP compared with RFD and hip joint flexion were increased following limb-loaded walking intervention in older adults.