Changes in maximum oxygen uptake during prolonged training, overtraining, and detraining in horses.

This research article investigates how different training phases including endurance training, high-intensity training, overload training and detraining impact Oxygen uptake (VO2max) in racehorses. Overtraining is found not to decrease VO2max, but a reduction is observed after six weeks of detraining.

Understanding the Research Design

• The research involved thirteen standardbred horses that underwent a series of training phases. These phases included: seven weeks of endurance training (phase 1), nine weeks of high-intensity training (phase 2), eighteen weeks of overload training (phase 3), and twelve weeks of detraining (phase 4).
• In phase 3, the horses were split into two groups: Overload Training (OLT) and Control (C). OLT group horses exercised at greater intensities, frequencies, and durations than the control group.

Key Findings

• Overtraining appeared after 31 weeks of training and was defined by a significant decrease in treadmill run time in response to a standardized exercise test.
• In the OLT group, a significant decrease in body weight was noted.
• At the end of phase 1, the Maximal oxygen uptake (VO2max), which is a measure of the maximum amount of oxygen a horse can use during intense exercise, increased by 15% from pretraining values of 117 +/- 2 (SE) ml.kg-1.min-1.
• When signs of overtraining were first seen in the OLT group, the VO2max was 29% higher than pretraining values, measured as 151 +/- 2 ml.kg-1.min-1 in both the OLT and C groups.
• VO2max did not show a significant reduction until six weeks into the detraining phase, when VO2max was recorded at 137 +/- 2 ml.kg-1.min-1.
• By the end of detraining (12 weeks), the mean VO2max was 134 +/- 2 ml.kg-1.min-1. This figure was still 15% above the pretraining values, indicating an enduring effect of the training, despite detraining attempts.
• When overtraining developed, VO2max was not different between the OLT and C groups. However, maximal values for CO2 production and the respiratory exchange ratio were lower in the OLT group.
• Importantly, overtraining was not linked to a decrease in VO2max and decreases in VO2max occurred slowly during detraining. This indicates that arduous training regimes may not negatively impact VO2max, but detraining periods can erode these improvements over time.