Published in:
01-01-2016 | Original Article
Gokyo Khumbu/Ama Dablam Trek 2012: effects of physical training and high-altitude exposure on oxidative metabolism, muscle composition, and metabolic cost of walking in women
Published in: European Journal of Applied Physiology | Issue 1/2016
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Purpose
We investigated the effects of moderate-intensity training at low and high altitude on \(\dot{V}\)O2 and \(\dot{Q}_{\text{a}} {\text{O}}_{ 2}\) kinetics and on myosin heavy-chain expression (MyHC) in seven women (36.3 yy ± 7.1; 65.8 kg ± 11.7; 165 cm ± 8) who participated in two 12- to 14-day trekking expeditions at low (598 m) and high altitude (4132 m) separated by 4 months of recovery.
Methods
Breath-by-breath \(\dot{V}\)O2 and beat-by-beat \(\dot{Q}_{\text{a}} {\text{O}}_{ 2}\) at the onset of moderate-intensity cycling exercise and energy cost of walking (C
w) were assessed before and after trekking. MyHC expression of vastus lateralis was evaluated before and after low-altitude and after high-altitude trekking; muscle fiber high-resolution respirography was performed at the beginning of the study and after high-altitude trekking.
Results
Mean response time of \(\dot{V}\)O2 kinetics was faster (P = 0.002 and P = 0.001) and oxygen deficit was smaller (P = 0.001 and P = 0.0004) after low- and high-altitude trekking, whereas \(\dot{Q}_{\text{a}} {\text{O}}_{ 2}\) kinetics and C
w did not change. Percentages of slow and fast isoforms of MyHC and mitochondrial mass were not affected by low- and high-altitude training. After training altitude, muscle fiber ADP-stimulated mitochondrial respiration was decreased as compared with the control condition (P = 0.016), whereas leak respiration was increased (P = 0.031), leading to a significant increase in the respiratory control ratio (P = 0.016).
Conclusions
Although training did not significantly modify muscle phenotype, it induced beneficial adaptations of the oxygen transport–utilization systems witnessed by faster \(\dot{V}\)O2 kinetics at exercise onset.