Table 4.
Total substrate oxidized during final 40 min of steady-state exercise.
| SL |
AHA |
CHA |
||||
|---|---|---|---|---|---|---|
| CHO | PLA | CHO | PLA | CHO | PLA | |
| Carbohydrate (g) glucose | ||||||
| Total∗† | 68.3 ± 19.8 | 45.9 ± 21.4 | 59.7 ± 18.9 | 42.9 ± 15.7 | 45.5 ± 13.3 | 28.2 ± 17.9 |
| Exogenous glucose† | 15.3 ± 2.2 | – | 7.4 ± 3.7 | – | 12.4 ± 2.3 | – |
| Other† | 53.0 ± 20.1 | 45.9 ± 21.4 | 52.3 ± 16.9 | 42.9 ± 15.7 | 33.0 ± 12.6 | 28.2 ± 17.9 |
| Fat∗† (g) | 7.5 ± 3.5 | 13.6 ± 6.6 | 9.1 ± 3.9 | 14.7 ± 3.5 | 15.2 ± 6.2 | 20.5 ± 8.5 |
| Protein∗ (g) | 3.1 ± 0.3 | 2.6 ± 0.8 | 3.1 ± 1.2 | 2.2 ± 0.3 | 3.4 ± 1.4 | 2.5 ± 0.4 |
Values are mean ± SD of total (g) substrate oxidized during final 40 min of 80 min steady-state exercise (treadmill walking) performed at sea level (SL), at 4,300 m altitude ∼5 h after arrival (acute high-altitude, AHA), and on the 22nd day of continuous residence at high-altitude (chronic high-altitude, CHA) of participants who ingested 1.8 g carbohydrate/min (CHO, n = 8, 65.25 g fructose + 79.75 g glucose) or placebo (PLA, n = 6) during exercise. “Other” carbohydrate oxidation was calculated by subtracting exogenous glucose oxidation from total carbohydrate oxidation, and for PLA, was entirely comprised of endogenous carbohydrate (i.e., glucose provided by muscle and liver glycogen stores) oxidation, but for CHO, was comprised of endogenous carbohydrate oxidation and exogenous fructose oxidation, the latter of which was not captured by the tracer techniques employed in the CHO group. ∗Main effect (P < 0.05) of treatment on total carbohydrate (CHO > PLA), fat (CHO < PLA) and protein (CHO > PLA) oxidation; †main effect (P < 0.05) of phase on total (CHA < SL, AHA) and other carbohydrate oxidation (CHA < SL, AHA), exogenous glucose oxidation (AHA < SL, CHA), and fat oxidation (CHA > SL, AHA).