Acute physiological and perceptual responses to high-load resistance exercise in hypoxia

This study assessed whether hypoxia during high-load resistance exercise could enhance the acute physiological responses related to muscular development. Twelve trained men performed exercise in three conditions: normoxia (fraction of inspired oxygen [F_I O₂ ] = 21%), moderate-level hypoxia (F_I O₂  = 16%) and high-level hypoxia (F_I O₂  = 13%). Exercise comprised high-load squats and deadlifts (5 × 5 using 80% of 1-repetition maximum with 180-s rest). Muscle oxygenation and activation were monitored during exercise. Metabolic stress was estimated via capillary blood sampling. Perceived fatigue and soreness were also quantified following exercise. While the hypoxic conditions appeared to affect muscle oxygenation, significant differences between conditions were only noted for maximal deoxyhaemoglobin in the deadlift (P = 0·009). Blood lactate concentration increased from 1·1 to 1·2 mmol l^-1 at baseline to 9·5-9·8 mmol l^-1 after squats and 10·4-10·5 mmol l^-1 after deadlifts (P≤0·001), although there were no between-condition differences. Perceived fatigue and muscle soreness were significantly elevated immediately and at 24 h following exercise, respectively, by similar magnitudes in all conditions (P≤0·001). Muscle activation did not differ between conditions. While metabolic stress is thought to moderate muscle activation and subsequent muscular development during hypoxic resistance training, it is not augmented during traditional high-load exercise. This may be explained by the low number of repetitions performed and the long interset rest periods employed during this training. These findings suggest that high-load resistance training might not benefit from additional hypoxia as has been shown for low- and moderate-load training.