Effects of short-term training on thermoregulatory and sweat responses during exercise in hot conditions.

This article studied the effects of short-term training in cool conditions on the thermoregulatory and sweat responses of horses during exercise in hot conditions. After undergoing moderate intensity treadmill training for ten days, horses demonstrated an improved ability to handle heat, with increased VO2max and reduced body temperatures during exercise.

Objective and Methodology

• The researchers aimed to determine whether a short-term training regimen in cool conditions would help improve a horse’s physiological responses – particularly their body temperature regulation and sweat responses – to exercising in hot conditions.
• Six unfit Thoroughbred horses were used for this study. They were subjected to a standardised treadmill exercise test (SET) in hot conditions before and after ten consecutive days of moderate-intensity training in cool conditions.
• The training consisted of running at 55% VO2max for 60 minutes. The SET included a warm-up, 40 minutes of trotting, 7 minutes at a higher intensity, and a 30-minute standing recovery. Throughout these exercises, various measurements were taken, including the horses’ heart rate, rectal, skin, pulmonary artery and muscle temperatures as well as sweat rate and sweat ion losses at 5-minute intervals.

Results and Conclusions

• The study found that training resulted in an average 8.9% increase in VO2max. This indicated an improvement in the horse’s cardiovascular fitness and their body’s ability to use oxygen effectively during exercise.
• The body temperatures recorded at the end of the exercise, including rectal, muscle, and pulmonary artery temperatures, were lower after the training, suggesting improved thermoregulation in hot conditions. However, there were no significant changes in sweat rate or sweat ion losses during the exercise after the training.
• Interestingly, the sweat rate and sweat losses during the recovery period after exercise were found to be lower post-training. This resulted in a reduction in total sweat fluid losses, with a comparable sweat ion loss rate. The researchers conclude that despite similar sweat rates during exercise post-training, the more rapid decrease during recovery contributed to the overall reduction in sweat fluid loss.
• The findings of this study shed light on how short-term training in cooler conditions can bolster the ability of horses to better handle heat during exercise. This can have implications for training strategies in regions where sudden shifts to high-temperature conditions are expected.