How fiber dynamics of plantarflexor and dorsiflexor muscles based on EMG-driven approach can explain the metabolic cost at different gait speeds

Abstract

Purpose: The aim of this study was to investigate the fiber dynamics of plantarflexor and dorsiflexor muscles and their association with the net metabolic rate (NC_w).

Methods: Metabolic, kinematic, kinetic, and electromyography measurements were made on seven young subjects while they walked on a force-plate instrumented treadmill at 1.00, 1.20, 1.40, 1.60, and 1.8 m/s for 1:30 min. The net metabolic rate was computed, and a one degree-of freedom EMG-driven approach was used to extract the force generation ability (F_ability), and active force-length (f_AL) and force-velocity (f_V) multiplier of each muscle. A one-way (speeds) repeated measures ANOVA was performed for each muscle and a multiple linear regression model was used to explain NC_w.

Results: F_ability was significantly affected by gait speed for the GasMed and the SOL muscles. The decrease of F_ability for the SOL and the GasMed was accompanied by a decrease in the force-velocity multiplier. The peak muscle force for the SOL increased for the lowest speed compared to the higher speed, and for the TibAnt increased at high speed compared to low speed. In addition, F_ability f_AL, and f_V of the SOL predicted over 58% of NC_w and F_Max of the TibAnt accounts for 39.9% of the variance in NC_w.

Conclusion: The increase of NC_w with gait speed over the preferred walking speed can be partially explained by the decreasing capacity of the SOL muscle to produce muscle force and more specifically by the force-velocity relationship and an increase in muscle force for the TibAnt.

Keywords: Fiber dynamics; Gait; Metabolic cost; Modeling.