The effect of treadmill incline on maximal oxygen uptake, gas exchange and the metabolic response to exercise in the horse.

This research investigates the physiological responses of horses during inclined treadmill exercise, focusing on its impact on maximal oxygen uptake (VO2,max), metabolic response – particularly lactate threshold (LT), and gas exchange mechanisms. The findings revealed a significantly higher VO2,max for inclined running, despite the lactate concentration remaining unchanged. It also indicated that inclined running prompts a different response in the horse that does not align with human responses to such conditions.

Introduction and Rationale

• The research identifies the gap in understanding about the effect of treadmill inclination on various physiological parameters in the exercising quadruped, specifically the horse.
• Its basis of comparison stems from prior knowledge about metabolic demand in humans and the associated effects of oxygen (O2) delivery on maximal O2 uptake, LT, and gas exchange during incremental exercise.
• The hypothesis of this study was that inclined running would increase the maximum rate of O2 uptake, and the rate of O2 uptake at LT and Tge in the subjects, translatable to six Thoroughbred horses used in the experiment.

Methodology

• Investigators utilised blood sampling and breath-by-breath expired gas analysis to measure exercise and respiration-related parameters.
• The exercise protocol was incremental running to volitional fatigue on a 10% incline gradient.

Results

• Findings indicate a significant increase in VO2,max (maximum rate of oxygen uptake) for inclined (I) running in comparison with level (L) running.
• Contrarily, peak plasma lactate concentration, a measure of metabolic stress, did not significantly differ between the two conditions.
• Relatively higher arterial Pco2, indicating relative hypoventilation, was observed for inclined running, suggesting an increase in the physiological stress in these conditions.
• Interestingly, gas exchange threshold (Tge) manifested under elevated stress conditions, and the Tge along with LT both occurred at a similar percentage of VO2,max, irrespective of the absolute level of VO2,max.
• In contrast to humans, LT is not a good predictor for Tge in horses.

Conclusion

• Clearly, the physiological processes within quadrupeds are distinctive from those seen in humans and are not purely dependent on the rate of oxygen uptake.
• The research reveals the need to revise training conditions for horses, taking into account the physiological transformations at the intersection of metabolic demand and gas exchange during exercise in these animals.