A 14-day acclimatization to severe altitude attenuated central fatigue during exercise compared to acute hypoxia (4% vs 8%, P<0.05), but did not eliminate peripheral fatigue (19% vs 21%, P=0.24).
Does a 14-day exposure to high altitude alter exercise-induced locomotor muscle fatigue compared to acute hypoxia and sea level?
Acclimatization to severe high altitude for 14 days attenuates central fatigue but not peripheral fatigue during locomotor exercise.
Absolute Event Rate: 4% vs 8%
p-value: p=<0.05
The development of muscle fatigue is oxygen (O2)-delivery sensitive arterial O2 content (CaO2) × limb blood flow (QL). Locomotor exercise in acute hypoxia (AH) is, compared with sea level (SL), associated with reduced CaO2 and exaggerated inspiratory muscle work (Winsp), which impairs QL, both of which exacerbate fatigue individually by compromising O2 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 O2, 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 (ΔQtw,pot). Central fatigue was expressed as the exercise-induced percent decrease in voluntary muscle activation (ΔVA). 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 O2/dl, respectively). Winsp during exercise increased with acclimatization (SL: 387 ± 36, AH: 503 ± 53, CH: 608 ± 67 cmH2O·s(-1)·min(-1); P < 0.01). Exercise at SL did not induce central or peripheral fatigue. ΔQtw,pot was significant but similar in AH and CH (21 ± 2% and 19 ± 3%; P = 0.24). ΔVA was significant in both hypoxic conditions but smaller in CH vs. AH (4 ± 1% vs. 8 ± 2%; P < 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.
Amann et al. (Sat,) reported a other. 14-day exposure to high altitude (chronic hypoxia) vs. Acute hypoxia and sea level was evaluated on Central fatigue (exercise-induced percent decrease in voluntary muscle activation) (p=<0.05). A 14-day acclimatization to severe altitude attenuated central fatigue during exercise compared to acute hypoxia (4% vs 8%, P<0.05), but did not eliminate peripheral fatigue (19% vs 21%, P=0.24).
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