The gait of pacers. 2: factors influencing pacing speed.

Standardbred pacers were studied at four different nominated speeds and selected gait kinematics were analysed to determine factors which contribute to pacing speed. A deterministic model is proposed in which pacing speed is a function of stride length and stride timing variables. Stance length and suspension time remained relatively constant over the different pacing speeds. Variables which discriminated best between pacing speeds were suspension length and overlap time. At near maximal speed, the pacers increased speeds with increased stride length. This was attributed to an increased suspension length with little difference in suspension times. A 22 per cent increase in pacing speed resulted in a 13 per cent increase in stride length, 26 per cent increase in suspension distance, 8 per cent increase in stride frequency, 35 per cent and 16 per cent increases in advanced placement and completion times and a 23 per cent decrease in the period of overlap.