Does altitude level of a prior time‐trial modify subsequent exercise performance in hypoxia and associated neuromuscular responses?

We examined the influence of prior time-trials performed at different altitudes on subsequent exercise in moderate hypoxia and associated cardiometabolic and neuromuscular responses. In normobaric hypoxia (simulated altitude 2000 m; FiO2: 0.163), 10 healthy males performed (1) an incremental test to exhaustion (VO2max_2000) and (2) a test to exhaustion at 80% of the power output associated to VO2max_2000 for a reference time (947 336 sec). Thereafter, two sessions were conducted in a randomized order: a cycle time-trial corresponding to the reference time (TT1) followed 22 min later (passive rest at 2000 m) by a 6-min cycle time-trial (TT2). TT1 was either performed at 2000 or 3500 m (FiO2: 0.135), while TT2 was always performed at 2000 m. As expected, during TT1, the mean power output (247 42 vs. 227 37 W; P < 0.001) was higher at 2000 than 3500 m. During TT2, the mean power output (256 42 vs. 252 36 W) did not differ between conditions. Before and after TT1, maximal isometric voluntary contraction torque in knee extensors (pooled conditions: 7.9 8.4%; P < 0.01), voluntary activation ( 4.1 3.1%; P < 0.05), and indices of muscle contractility (peak twitch torque: 39.1 11.9%; doublet torques at 100 Hz: 15.4 8.9%; 10/100 Hz ratio: 25.8 7.7%; all P < 0.001) were equally reduced at 2000 m or 3500 m. Irrespective of the altitude of TT1, neuromuscular function remained similarly depressed after TT1 both before and after TT2 at 2000 m. A prior time-trial performed at different altitude influenced to the same extent performance and associated cardiometabolic and neuromuscular responses during a subsequent exercise in moderate hypoxia.