LIMB SKELETAL-MUSCLE ADAPTATION IN ATHLETES AFTER TRAINING AT ALTITUDE

Morphological and biochemical characteristics of biopsies obtained from gastrocnemius (GAS) and triceps brachii muscle (TRI), as well as maximal O2 uptake (V̇O2(max)) and O2 deficit, were determined in 10 well-trained cross-country skiers before and after a 2-wk stay (2,100 m above sea level) and training (2,700 m above sea level) at altitude. On return to sea level, V̇O2(max) was the same as the prealtitude value, whereas an increase in O2 deficit (29%) and in short-term running performance (17%) was observed (P < 0.05). GAS showed maintained capillary supply but a 10% decrease in mitochondrial enzyme activities (P < 0.01), whereas an increase in capillary supply (P < 0.05) but unchanged mitochondrial enzyme activities were observed in TRI. Buffer capacity was increased by 6% in both GAS and TRI (P < 0.05). A positive correlation was found between the relative increase in buffer capacity of GAS and short-term running time (P < 0.05). Thus the present study indicates no effect of 2 wk of altitude training on V̇O2(max) but provides evidence to suggest an improvement in short-term exercise performance, which may be the result of an increase in muscle buffer capacity.