High-speed gallop locomotion in the Thoroughbred racehorse. I. The effect of incline

During locomotion up an incline, power is required to elevate the centre of mass. This is provided when the animalʼs limbs are in contact with the ground. Measurements of stride timing variables from multiple limbs during high speed, over-ground locomotion would enhance our understanding of locomotor powering during changes in terrain. This study measured foot-on and foot-off times from galloping horses using a previously validated system of limb-mounted accelerometers and a global positioning system data logger. A detailed track survey provided incline information from all areas of the track. Measurements were made from six horses over a speed range of 9 to 13·m·s–1. Foot-fall timings were used to calculate variables, which included stance duration, protraction duration, stride frequency and duty factor. The relationship between track incline and measured variables was assessed. Stride variables from horses galloping on level (0–2% incline) and incline (8–12% incline) sections of the track were compared. Fore- and hindlimb protraction durations were significantly reduced across the speed range during incline galloping (P=0.001). This resulted in a mean increase in stride frequency from 2.01 to 2.08·strides·s–1 at 9.5·m·s–1 and 2.10 to 2.17·strides·s–1 at 12.5·m·s–1 during incline galloping. Duty factor was significantly greater for the hindlimbs during incline galloping (P