Table 2.

Effects of training in the fasted state vs. training in the carbohydrate-fed state on respiratory gas exchange during a 2-h constant-load exercise bout

	F			CHO
	Minute 10	Minute 60	Minute 120	Minute 10	Minute 60	Minute 120
V̇o2, l/min
Pretest	2.68 ± 0.15	2.83 ± 0.17	2.89 ± 0.17	2.69 ± 0.14	2.80 ± 0.15	2.83 ± 0.18
Posttest	2.66 ± 0.13	2.68 ± 0.10	2.83 ± 0.12	2.66 ± 0.15	2.75 ± 0.13	2.89 ± 0.13
V̇co2, l/min
Pretest	2.51 ± 0.11	2.56 ± 0.13	2.59 ± 0.13	2.53 ± 0.14	2.54 ± 0.13	2.54 ± 0.17
Posttest	2.32 ± 0.13*	2.24 ± 0.11*	2.32 ± 0.13*	2.29 ± 0.15*	2.28 ± 0.11*	2.34 ± 0.12*
RER
Pretest	0.94 ± 0.02	0.91 ± 0.02	0.90 ± 0.02	0.94 ± 0.02	0.91 ± 0.02	0.90 ± 0.02
Posttest	0.87 ± 0.01*	0.84 ± 0.01*	0.82 ± 0.01*	0.86 ± 0.02*	0.83 ± 0.02*	0.81 ± 0.02*
Fat oxidation rate, g/min
Pretest	0.29 ± 0.09	0.44 ± 0.11	0.50 ± 0.11	0.27 ± 0.07	0.43 ± 0.09	0.48 ± 0.09
Posttest	0.56 ± 0.06*	0.78 ± 0.05*	0.85 ± 0.06*	0.61 ± 0.07*	0.85 ± 0.08*	0.92 ± 0.07*
Carbohydrate oxidation rate, g/min
Pretest	2.79 ± 0.14	2.58 ± 0.23	2.50 ± 0.20	2.86 ± 0.23	2.58 ± 0.21	2.47 ± 0.29
Posttest	2.03 ± 0.23*	1.62 ± 0.19*	1.48 ± 0.24*	1.89 ± 0.24*	1.52 ± 0.20*	1.37 ± 0.22*

Data provided are means ± SE (F: n = 10; CHO: n = 9) and represent values before (pretest) and after (posttest) a 6-wk training period in either the fasted state (F) or with ample carbohydrate intake before and during the training sessions (CHO). The respiratory data represent measurements at the start (at minute 10), halfway through (at minute 60), and at the end (at minute 120) of a 2-h constant-load exercise bout. The workload was 175 ± 6 W and corresponded to 65% of V̇o_2max in the pretest vs. 60% of V̇o_2max in the posttest. Fat and carbohydrate oxidation rates were calculated using the nonprotein respiratory quotient. V̇o₂, oxygen uptake; V̇co₂, carbon dioxide output; RER, respiratory exchange ratio.

^*P < 0.05 vs. pretest.