Oxygen consumption (VO2) during trotting on a 10% decline.

This study investigates how oxygen consumption and stride frequency in horses might decrease when trotting downhill, compared to running on a flat surface. The research suggests that trotting downhill could be less energy-demanding and equally safe for the animals.

Research Objectives

• The research aims to explore the effects of a 10% decline in surface gradient on trotting horses, specifically focusing on the rate of oxygen consumption and stride frequency.
• The study’s objective was driven by the lack of existing measurements on decline locomotion in horses, although measures for level and incline locomotion were available. Moreover, there was a general perception that decline locomotion could potentially cause muscle damage due to eccentric contractions.
• The research aims to challenge this notion by hypothesizing that the rate of O2 consumption and stride frequency would decrease, implying less physical exertion for the horse on a 10% decline compared to level ground.

Methodology

• The study involved six horses, each weighing an average of 467 +/- 68 kg. The horses were acclimated to trotting on level ground and a decline before the data collection process.
• Oxygen consumption under moderate conditions was measured during trotting between 2.25 and 4.0 m/sec (with 0.25 m/sec increments) on a treadmill on level ground and a 10% decline.
• The stride frequencies were manually counted. The speed at which the minimum Cost of Transport (COT) occurred on the decline versus the level ground was also noted.

Results

• The results indicated that the average oxygen consumption (VO2) decreased by 45% when the horses trotted on a 10% decline, implying that it was less strenuous for them to do so.
• Stride frequency also decreased by 2.7% on the decline. However, the speed at which the minimum COT occurred was faster downhill than on a flat surface.
• There was no evidence of muscle soreness in response to the downhill trotting, suggesting that this form of exercise was relatively safe for the horses.

Conclusions

• These findings suggested that downhill trotting, eccentric exercise, is not only safe for horses, but also requires almost half the energetic costs as trotting on level ground.
• The study, however, does not provide insights into whether the 10% decline is the most optimum gradient for downhill trotting or if the horse adjusts its preferred speed to accommodate downhill trotting.