Live high: train low increases muscle buffer capacity and submaximal cycling efficiency

This study investigated whether hypoxic exposure increased muscle buffer capacity (<i>β</i>m) and mechanical efficiency during exercise in male athletes. A control (CON, <i>n</i>=7) and a live high:train low group (LHTL, <i>n</i>=6) trained at near sea level (600 m), with the LHTL group sleeping for 23 nights in simulated moderate altitude (3000 m). Whole body oxygen consumption (V˙O₂) was measured under normoxia before, during and after 23 nights of sleeping in hypoxia, during cycle ergometry comprising 4×4-min submaximal stages, 2-min at 5.6 ± 0.4 W kg^–1, and 2-min 'all-out' to determine total work and V˙O_2peak. A vastus lateralis muscle biopsy was taken at rest and after a standardized 2-min 5.6 ± 0.4 W kg^–1 bout, before and after LHTL, and analysed for <i>β</i>m and metabolites. After LHTL, <i>β</i>m was increased (18%, <i>P</i> < 0.05). Although work was maintained, V˙O_2peak fell after LHTL (7%, <i>P</i> < 0.05). Submaximal V˙O₂ was reduced (4.4%, <i>P</i> < 0.05) and efficiency improved (0.8%, <i>P</i> < 0.05) after LHTL probably because of a shift in fuel utilization. This is the first study to show that hypoxic exposure, per se, increases muscle buffer capacity. Further, reduced V˙O₂ during normoxic exercise after LHTL suggests that improved exercise efficiency is a fundamental adaptation to LHTL.<br /><br /><br />