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

Abstract : 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; FiO 2 : 0.163), 10 healthy males performed (1) an incremental test to exhaustion (VO 2max_2000) and (2) a test to exhaustion at 80% of the power output associated to VO 2max_2000 for a reference time (947 AE 336 sec). Thereafter , two sessions were conducted in a randomized order: a cycle time-trial corresponding to the reference time (TT 1) followed 22 min later (passive rest at 2000 m) by a 6-min cycle time-trial (TT 2). TT 1 was either performed at 2000 or 3500 m (FiO 2 : 0.135), while TT 2 was always performed at 2000 m. As expected, during TT 1 , the mean power output (247 AE 42 vs. 227 AE 37 W; P < 0.001) was higher at 2000 than 3500 m. During TT 2 , the mean power output (256 AE 42 vs. 252 AE 36 W) did not differ between conditions. Before and after TT 1 , maximal isometric voluntary contraction torque in knee exten-sors (pooled conditions: À7.9 AE 8.4%; P < 0.01), voluntary activation (À4.1 AE 3.1%; P < 0.05), and indices of muscle contractility (peak twitch torque: À39.1 AE 11.9%; doublet torques at 100 Hz: À15.4 AE 8.9%; 10/100 Hz ratio: À25.8 AE 7.7%; all P < 0.001) were equally reduced at 2000 m or 3500 m. Irrespective of the altitude of TT 1 , neuromuscular function remained similarly depressed after TT 1 both before and after TT 2 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.
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Olivier Girard, Simone Bula, Franck Brocherie, Guillaume Millet, Raphael Faiss, et al.. Does altitude level of a prior time-trial modify subsequent exercise performance in hypoxia and associated neuromuscular responses?. Physiological Reports, Wiley, 2016, 4 (14), pp.e12804. ⟨10.14814/phy2.12804⟩. ⟨hal-01793576⟩

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