Speaking of hypoxia, a new study published in Physiological Reports examined how training for 2 weeks under 18% hypoxia impacts muscles of Thoroughbred horses. Unlike humans, these horses do not increase production of red blood cells to enhance oxygen transport throughout the body under hypoxic conditions. This difference led researchers to speculate that the horses had other ways of adapting to exercise.
In the new study, horses were trained 3 days a week to run for 2 minutes at 95% of their maximal oxygen consumption on a rather large treadmill. After the training period, horses underwent an incremental exercise test under normal oxygen conditions. The researchers found that the animals trained under hypoxic conditions were able to exercise longer during the incremental exercise test. This ability to increase exercise duration may be due to changes that occurred within the skeletal muscles of the animals. Specifically, the researchers found the muscles had increased metabolic pathways that do not rely on oxygen and were better able to dispose of lactate.
W Wang, K Mukai, K Takahashi, H Ohmura, T Takahashi, H Hatta, Y Kitaoka. Short‐term hypoxic training increases monocarboxylate transporter 4 and phosphofructokinase activity in Thoroughbreds. Physiological Reports. 8(11): e14473, 2020. https://doi.org/10.14814/phy2.14473