Four weeks of high-intensity training in moderate, but not mild hypoxia improves performance and running economy more than normoxic training in horses.

The study explored the impact of training horses in different oxygen conditions – moderate hypoxia, mild hypoxia, and normoxia. Results indicate that training horses in moderate hypoxia for four weeks leads to better performance and more efficient running than in normal oxygen conditions. These benefits remain for two weeks even after returning to normal oxygen levels.

Research Goals and Methodology

• The researchers wanted to understand how training horses in various oxygen levels (hypoxia and normoxia) would affect their performance and aerobic capacity.
• Hypoxia, or low oxygen conditions, were divided into two categories: moderate (H16, with an oxygen fraction of 16%) and mild (H18, with an oxygen fraction of 18%). Normoxia (N21) represented normal oxygen conditions with an oxygen fraction of 21%.
• Seven untrained Thoroughbred horses underwent a 4-week training protocol. The protocol included three weekly sessions of 2-minute cantering at 95% of the horse’s maximum oxygen consumption in the specified oxygen conditions.
• This was followed by two weeks of normoxic training to see if the benefits from the hypoxic training would last.
• The research design was a randomized crossover study with a 3-month washout period. This design ensures that each horse experienced all three training conditions over a period of time.
• Their performance was monitored through incremental treadmill tests at the start of the study, after the 4-week training, and after two weeks of post-hypoxic training in normoxia.

Findings

• The study findings showed that horses’ running time during the treadmill tests significantly improved in moderate hypoxia (H16) and mild hypoxia (H18), as compared to normoxia.
• Only in moderate hypoxia (H16) there was a significant increase in the horses’ speed when they reached their maximum oxygen consumption.
• Maximum oxygen consumption and cardiac output at exhaustion increased in all groups after the 4-week training period. However, there was no significant difference in these aspects between the three groups.
• The improvements held steady even two weeks into the post-hypoxic training period in normoxia. Variables like running time, maximum speed, and lactate threshold didn’t decrease in any group during this period.
• This conclusively suggests that a 4-week moderate hypoxic training regimen can enhance a horse’s performance more than normoxic training and that these benefits can persist at least 2 weeks after returning to normoxia.