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

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• 作者：Olivier Girard ; Simone Bula ; Raphaël Faiss ; Franck Brocherie ; Guillaume Y. Millet ; Grégoire P. Millet
• 刊名：Physiological Reports
• 出版年：2016
• 出版时间：July 2016
• 年：2016
• 卷：4
• 期：14
• 全文大小：193.8KB
• ISSN：2051-817X

文摘

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 (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 &plusmn; 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 &plusmn; 42 vs. 227 &plusmn; 37 W; m>Pm> < 0.001) was higher at 2000 than 3500 m. During TT₂, the mean power output (256 &plusmn; 42 vs. 252 &plusmn; 36 W) did not differ between conditions. Before and after TT₁, maximal isometric voluntary contraction torque in knee extensors (pooled conditions: &minus;7.9 &plusmn; 8.4%; m>Pm> < 0.01), voluntary activation (&minus;4.1 &plusmn; 3.1%; m>Pm> < 0.05), and indices of muscle contractility (peak twitch torque: &minus;39.1 &plusmn; 11.9%; doublet torques at 100 Hz: &minus;15.4 &plusmn; 8.9%; 10/100 Hz ratio: &minus;25.8 &plusmn; 7.7%; all m>Pm> < 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.