Résumé
Introduction: This study examined the influence of alterations in maximal oxygen uptake ((V) over dotO(2max)) in mediating performance and pacing during prolonged self-paced exercise. Methods: Twelve well-trained cyclists completed a 750-kJ time trial in temperate (COOL, 18 degrees C), hot (HOT, 35 degrees C), and hypoxic (HYP, 18 degrees C; FiO(2), 0.145) conditions, creating models with a stable, progressively decreasing, and acutely decreased (V) over dotO(2max), respectively. Results: Trial completion was faster in COOL (48.2 +/- 5.7 min) compared with HOT (55.4 +/- 5.0 min) and HYP (60.1 +/- 6.5 min) (P < 0.001), with HOT being faster than HYP (P = 0.028). Core temperature reached 39.0 degrees C +/- 0.6 degrees C (COOL), 39.8 degrees C +/- 0.5 degrees C (HOT), and 38.5 degrees C +/- 0.4 degrees C (HYP; P < 0.01). Power output during COOL was higher than HOT from 40% of work completed onward (P < 0.05) and for the entirety of HYP (P < 0.001), in which it was lower than HOT at 20%-30% (P < 0.05). Normalized power output during COOL and HYP varied by similar to 13% and similar to 16%, respectively, whereas a similar to 27% variation occurred in HOT. (V) over dotO(2) in COOL was higher than HOT from 70% onward (P < 0.01) and higher than HYP throughout exercise (P < 0.001). Relative to baseline (V) over dotO(2max) (%(V) over dotO(2max)) in normoxia (COOL and HOT) and hypoxia (HYP), %(V) over dotO(2max) during HOT (78% +/- 8%) was lower than COOL (84% +/- 7%; P = 0.005) and HYP (87% +/- 5%; P = 0.003). Conclusions: Despite an acutely reduced (V) over dotO(2max) and power output in HYP, pacing and %(V) over dotO(2max) were similar to COOL. In contrast, the progressive decrease in (V) over dotO(2max) and power output in HOT resulted in a more variable pacing pattern with %(V) over dotO(2max) decreasing throughout exercise. These data support the premise that pacing is associated with maintaining an optimal performance intensity, in conjunction with acute and progressive alterations in (V) over dotO(2max).