Meeting Abstract
122.1 Tuesday, Jan. 7 13:30 How do movement speed and terrain visibility influence neuromuscular control of bipedal locomotion? GORDON, J.C.*; RANKIN, J.W.; WILSON, A.M.; DALEY, M.A.; Royal Veterinary College, UK; Royal Veterinary College, UK; Royal Veterinary College, UK; Royal Veterinary College, UK jcgordon@rvc.ac.uk
Bipedal locomotion requires dynamic stability accomplished via complex interactions of sensory information, neuromuscular control and intrinsic mechanics. To prevent falls and maintain desired movement, control must seamlessly adapt for both anticipated and unexpected perturbations. Previous guinea fowl obstacle negotiation studies suggested different behavioural strategies for stability depending on whether birds ran over ground or on a treadmill. One hypothesized reason for the difference is reduced obstacle visibility on a treadmill. To further investigate context-dependent shifts in neuromuscular control we presented high and low contrast obstacles to guinea fowl (Numida Meleagris, N = 6) walking (0.7ms-1) and running (1.3ms-1) on a treadmill. We recorded muscle activity using indwelling electromyography (EMG) in 8 hind limb muscles. Manipulating obstacle contrast induced only subtle myoelectric shifts across all muscles. However, treadmill speed substantially influenced obstacle negotiation strategy. We observed larger total intensity shifts across hind limb muscles in walking compared to running, with greater anticipatory muscle activity shifts in proximal muscles, and larger reactive changes in distal muscles. We also observed larger variations in swing-stance timing during walking. Across terrain conditions, principle component analysis revealed that 2PCs can explain 85% of muscle activity variance, the 1st PC (63%) representing co-variance in a hip flexor and distal extensors, and the 2nd PC (22%) representing co-variance in hip extensors. Our findings provide direct evidence for speed-dependent shifts in control, with a greater reliance on stride-to-stride neural adjustments at slow speed, shifting towards feed-forward activation and intrinsic mechanical stability at high speed.
