Abstract
During locomotion up an incline, power is required to elevate the centre of mass. This is provided when the animal's 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<0.001), increasing from 0.31 to 0.32 at 9.5 m s(-1) and 0.28 to 0.29 at 12.5 m s(-1). Peak limb force was calculated from duty factor and assumed fore- to hindlimb impulse distributions. Smaller peak vertical forces were calculated in the forelimbs and increased peak vertical forces were calculated in the hindlimbs when galloping on an incline. Measured changes in stride timing variables differ from those reported in trotting horses. We propose that horses increase their stride frequency at a given speed during incline galloping to provide power for moving the centre of mass up the slope.
Highlights
During incline running, positive mechanical work is performed to move the animal’s centre of mass (CoM) up the slope
Changes in stride timing variables may provide an insight into the mechanism of powering inclined high speed locomotion
Our results provide an opportunity to identify relationships between stride timing variables and the power required by the horse to move up an incline
Summary
Positive mechanical work is performed to move the animal’s centre of mass (CoM) up the slope. Changes in stride timing variables may provide an insight into the mechanism of powering inclined high speed locomotion. Recent technological advances have allowed the accurate measurement of stride timing variables in galloping horses travelling at a range of speeds over ground (Parsons and Wilson, 2006; Witte et al, 2006; Witte et al, 2004). Measured variables, including stance duration, protraction duration and stride frequency, improve our understanding of the athletic ability of animals (Usherwood and Wilson, 2005; Weyand et al, 2000), the metabolic cost of locomotion (Kram and Taylor, 1990), limb forces (Alexander et al, 1979; Witte et al, 2006; Witte et al, 2004) and gait transitions (Farley and Taylor, 1991; Kram and Taylor, 1990; Weyand et al, 2000)
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