Module contributions to the walking subtasks of body support, forward propulsion and leg swing in the beginning of early stance (∼15% gait cycle), late stance (∼45% gait cycle), early swing (∼70 % gait cycle) and late swing (∼85% gait cycle). Arrows acting on the center-of-mass symbol indicate the resultant module contributions to the horizontal and vertical ground reactions forces that act to accelerate the body center-of-mass to provide body support and forward propulsion. Net energy flow by each individual module to the trunk or leg (“net” total of all modules also presented for leg) is denoted by a “+” (energy increase) or “-” (energy decrease). In early stance, Modules 1 and 2 provide body support while acting to decelerate forward motion while Module 4 and all Other muscles combined to provide a little body support and forward propulsion. In late stance, Module 2 provides both body support and forward propulsion. All Others includes the contributions by BFsh, IL, PER and GMAX.