Meeting Abstract
Terrestrial vertebrates achieve agile and robust locomotion in the face of changing task demands and variable terrain; yet, the integration of sensory and biomechanical processes underlying this performance remains poorly understood. Here we investigate the relative roles of intrinsic mechanics and proprioceptive feedback in the modulation of muscle dynamics, using a novel bilateral self-reinnervation protocol to induce proprioceptive loss in the lateral gastrocnemius muscle (LG) of the guinea fowl (Numida meleagris). Previous studies of guinea fowl locomotion revealed that LG rapidly adjusts work output for stability in uneven terrain. However, reflex-mediated changes occurred concurrently with intrinsic mechanical effects, making their relative roles unclear. We measured in vivo LG force-length dynamics during running over level and obstacle terrain in guinea fowl lacking autogenic LG proprioception. Birds showed no consistent shifts in LG muscle electromyographic (EMG) activity during obstacle negotiation, yet, substantial shifts in LG force and work. The magnitude and pattern of work modulation matched that previously observed in ‘intact’ birds. In obstacle encounters, reinnervated LG exhibited higher muscle strain during force development, associated with higher total force and work output. The findings suggest that autogenic proprioception is not essential for regulating muscle dynamics during running. Instead, feed-forward control coupled to intrinsic mechanics can provide robust performance. We will discuss the likely roles of proprioception in light of this evidence, including provision of error signals to update internal models and optimising muscle strain for economy and injury avoidance.
