Moderate‐intensity training in hypoxia improves exercise performance and glycolytic capacity of skeletal muscle in horses

We investigated whether moderate‐intensity training of horses in moderate hypoxia for 4 weeks elicits greater adaptations in exercise performance, aerobic capacity, and glycolytic/oxidative metabolism in skeletal muscle compared to normoxic training. In a randomized crossover study design, seven untrained Thoroughbred horses (5.9 ± 1.1 years, 508 ± 9 kg) completed 4 weeks (3 sessions/week) of two training protocols consisting of 3‐min cantering at 70% of maximal oxygen consumption (V˙O2max) in hypoxia (HYP; FIO2 = 14.7%) and normoxia (NOR; FIO2 = 21.0%) with a 4‐month washout period. Normoxic incremental exercise tests (IET) were conducted before and after training. Biopsy samples were obtained from the middle gluteal muscle before IET and monocarboxylate transporter (MCT) protein expression and glycolytic/mitochondrial enzyme activities were analyzed. Data were analyzed using mixed models (p