AltitudeOmics: on the consequences of high-altitude acclimatization for the development of fatigue during locomotor exercise in humans

作者：Amann Markus^*; Goodall Stuart; Twomey Rosie; Subudhi Andrew W; Lovering Andrew T; Roach Robert C

来源：Journal of Applied Physiology, 2013, 115(5): 634-642.

DOI：10.1152/japplphysiol.00606.2013

• altitude
• respiratory muscle work
• arterial O-2 content
• cerebral blood flow

The development of muscle fatigue is oxygen (O-2)-delivery sensitive [arterial O-2 content (CaO2) +/- limb blood flow (Q(L))]. Locomotor exercise in acute hypoxia (AH) is, compared with sea level (SL), associated with reduced CaO2 and exaggerated inspiratory muscle work (W-insp), which impairs QL, both of which exacerbate fatigue individually by compromising O-2 delivery. Since chronic hypoxia (CH) normalizes CaO2 but exacerbates Winsp, we investigated the consequences of a 14-day exposure to high altitude on exercise-induced locomotor muscle fatigue. Eight subjects performed the identical constant-load cycling exercise (138 +/- 14 W; 11 +/- 1 min) at SL (partial pressure of inspired O-2, 147.1 +/- 0.5 Torr), in AH (73.8 +/- 0.2 Torr), and in CH (75.7 +/- 0.1 Torr). Peripheral fatigue was expressed as pre- to postexercise percent reduction in electrically evoked potentiated quadriceps twitch force (Delta Q(tw,pot)). Central fatigue was expressed as the exercise-induced percent decrease in voluntary muscle activation (Delta VA). Resting CaO2 at SL and CH was similar, but CaO2 in AH was lower compared with SL and CH (17.3 +/- 0.5, 19.3 +/- 0.7, 20.3 +/- 1.3 ml O-2/dl, respectively). Winsp during exercise increased with acclimatization (SL: 387 +/- 36, AH: 503 +/- 53, CH: 608 +/- 67 cmH(2)O.s(-1).min(-1); P %26lt; 0.01). Exercise at SL did not induce central or peripheral fatigue. Delta Q(tw,pot) was significant but similar in AH and CH (21 +/- 2% and 19 +/- 3%; P = 0.24). Delta VA was significant in both hypoxic conditions but smaller in CH vs. AH (4 +/- 1% vs. 8 +/- 2%; P %26lt; 0.05). In conclusion, acclimatization to severe altitude does not attenuate the substantial impact of hypoxia on the development of peripheral fatigue. In contrast, acclimatization attenuates, but does not eliminate, the exacerbation of central fatigue associated with exercise in severe AH.

• 出版日期2013-9