Live high:train low increases muscle buffer capacity and submaximal cycling ef®ciency

This study investigated whether hypoxic exposure increased muscle buffer capacity (bm) and mechanical ef®ciency during exercise in male athletes. A control (CON, n ˆ 7) and a live high:train low group (LHTL, n ˆ 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, and 2-min `all-out' to determine total work and _ V O2peak. A vastus lateralis muscle biopsy was taken at rest and after a standardized 2min 5.6 ‹ 0.4 W kg bout, before and after LHTL, and analysed for bm and metabolites. After LHTL, bm was increased (18%, P < 0.05). Although work was maintained, _ V O2peak fell after LHTL (7%, P < 0.05). Submaximal _ V O2 was reduced (4.4%, P < 0.05) and ef®ciency improved (0.8%, P < 0.05) after LHTL probably because of a shift in fuel utilization. This is the ®rst 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 ef®ciency is a fundamental adaptation to LHTL.