V(O2) recovery kinetics in the horse following moderate, heavy, and severe exercise.

This research studied how quickly horses restore their oxygen levels (VO2) after different exercise intensities. The findings suggest that the VO2 recovery rate is generally similar regardless of whether the exercise was moderate, heavy, or severe, but following heavy and severe workouts, the horse’s VO2 levels were higher than before the exercise.

Research Purpose

This research was performed to understand the recovery kinetics of oxygen uptake (VO2) in horses post-exercise. The research aimed to characterize the recovery VO2 kinetics at varying levels of intensity – moderate (M), heavy (H), and severe (S) exercise domains.

Methodology

• Six horses were put through treadmill running sessions at different exercise intensities matching approximately 50, 85, and 100% of peak VO2.
• The recovery periods were modeled using a three-phase model with a single-exponential (fast component) or double-exponential (fast and slow component) phase 2.
• Time delay and the fast-component time constants were measured from each exercise intensity domain.
• In the H and S domains, the post-exercise VO2 was also observed and was compared to pre-exercise baseline.
• The additional post-exercise VO2 and the end-exercise increase in lactate were correlated.

Results

• The single-exponential phase 2 model fitted the data for most of the horses exceptionally well, except for one horse from the H domain, which fitted best with a double-exponential.
• The time delay showed no domain dependency, meaning it didn’t vary based on exercise intensity.
• The fast-component time constants also didn’t change with differing exercise intensity.
• In the H and S domains, the VO2 following the resolution was above the pre-exercise baseline, marking an increase in the VO2 level post-exercise in these domains.
• The additional post-exercise VO2 correlated strongly with the end-exercise increase in lactate (r = 0.94, P 0.05).

Conclusion

The time delay and the subsequent kinetic response of the primary phase of VO2 recovery in horses were found to be independent of the preceding exercise-intensity domain. However, in the heavy and severe domains, after the fast component was resolved, the VO2 levels were elevated from their baseline.