Meeting Abstract

P1.171  Monday, Jan. 4  Variability of Walking: Size and Neural Activation Patterns in Calf Muscles of Runners NGUYEN, C.*; DAVIDSON, B.; KANG, J.; KOH, S.; AHN, A.; Harvey Mudd, Claremont cassie_nguyen@hmc.edu

Almost all humans walk, but the morphology of their leg muscles and their gait patterns differ visibly between individuals. In a previous study, sedentary adults used two patterns of neural signals. Half of the subjects used their medial gastrocnemius muscles (MG) more strongly than their lateral gastrocnemius muscles (LG) at most walking speeds (“MG-biased”). The other half walked activating both muscles equally (“unbiased”). The MG-biased subjects also had thicker MG muscles and smaller mechanical advantage at the ankle. In this study, we hypothesized that regular training results in the convergence of the neural recruitment patterns and relative size of the calf muscles despite differences in mechanical advantage. In recreational runners, we measured muscle thickness of the MG and LG muscles at rest and mechanical advantage. Then, we obtained joint kinematics (Qualysis, 125 fps) and recorded muscle activity patterns using surface electromyography, normalized to maximum voluntary contractions while walking on a treadmill at 6 speeds. Of the 17 runners, 7 subjects used an MG-biased recruitment strategy and 10 subjects used an unbiased strategy while walking. Additionally, when normalized to lower leg length, MG-biased runners had thicker relative MG muscles (0.059 ± 0.004) than unbiased runners (0.052 ± 0.005; p = 0.05). The mechanical advantage about the ankle, however, was larger for MG-biased subjects (0.23 ± 0.05) than for unbiased subjects (0.19 ± 0.05; p = 0.05). Despite these morphological differences, the two groups had similar kinematics while walking. The two recruitment strategies in runners suggest that training reinforces the different neural recruitment patterns also observed in sedentary individuals. Training may alter the influence of mechanical advantage on neural recruitment strategies and muscle size. This study was supported by the Barbara Stokes Dewey Endowment and HHMI.