A method to determine mechanical energy conservation and efficiency in equine gait: a preliminary study.

This research article conducts a preliminary study exploring the method to calculate mechanical energy conservation and efficiency in a horse’s gait by combining metabolic and mechanical energy costs of locomotion across a range of trotting speeds on a treadmill.

Objective

The aim of the pilot study was to understand and measure both metabolic and mechanical energy costs of horse locomotion at various trotting speeds of 2.5 to 6.2 m/s on a level treadmill.

Methodology

• The researchers used a single, well-conditioned Thoroughbred horse for their study.
• The horse was theoretically modeled as a system of 15 linked segments, taking into consideration all the four limbs, head, neck, and trunk.
• An incremental exercise test involving increasing trotting speeds was conducted while VO2 was documented using a breath-by-breath gas analysis system.
• Simultaneously, positional data were gathered at a frequency of 100 Hz using a two-camera infrared kinematic system.
• They evaluated the mechanical energy cost for every 3-6 strides per speed increment, and metabolic data were collated during the last 15 seconds of every speed step.

Findings

• The mechanical energy cost showcased linear increase starting from 3.3 J/kg/m at 2.5 m/s to 5.31 J/kg/m at 6.2 m/s, with little within-subject variability at each speed step.
• Energy exchange within and between segments was considered, accounting for significant energy-conserving mechanisms in the link-segment model.
• The energy conservation within each segment was roughly constant as speed increased, whereas energy conservation between segments rose from 1040 to 4502 J/stride.
• An ‘apparent’ efficiency was revealed across the speed increments when combining the metabolic and mechanical costs of locomotion, showing an inverted bell-shaped curve.
• The maximum efficiency value was marked at the speed of 3.8 m/s where metabolic cost was recorded the lowest.