Table 2.

Peak values of the main investigated variables determined at voluntary exhaustion during the incremental knee‐extension exercise

	BDC	N‐BR	H‐BR	H‐AMB
Power outputpeak (W)	49.1 ± 9.4	47.8 ± 6.1	45.7 ± 12.2	50.4 ± 14.2
${\dot{V}}_{\mathrm{E}\mathrm{peak}}$ (L min−1)	45.6 ± 14.5	49.0 ± 24.7	48.2 ± 13.8	43.0 ± 7.2
${\dot{V}}_{\mathrm{T}\mathrm{peak}}$ (L)	1.55 ± 0.38	1.59 ± 0.55	1.62 ± 0.57	1.48 ± 0.40
fRpeak (br min−1)	29.6 ± 9.1	30.8 ± 9.2	29.9 ± 5.7	29.0 ± 7.2
${\dot{V}}_{{\mathrm{O}}_2\mathrm{peak}}$ (L min−1)	1.06 ± 0.15	0.98 ± 0.13*	0.96 ± 0.17*	1.05 ± 0.16
${\dot{V}}_{{\mathrm{O}}_2\mathrm{peak}}$/TM mass (mL kg−1 min−1)	150.0 ± 22.8	148.1 ± 23.5	147.2 ± 30.5	161.3 ± 30.8*
${\dot{V}}_{\mathrm{C}{\mathrm{O}}_2\mathrm{peak}}$ (L min−1)	1.23 ± 0.21	1.19 ± 0.19*	1.12 ± 0.23*	1.21 ± 0.20
R peak	1.18 ± 0.16	1.21 ± 0.15	1.18 ± 0.15	1.15 ± 0.11
$P_{\mathrm{ET}{\mathrm{O}}_2\mathrm{peak}}$ (mmHg)	104.6 ± 6.1	105.9 ± 6.2	107.8 ± 4.1	104.1 ± 2.6
$P_{\mathrm{ETC}{\mathrm{O}}_2\mathrm{peak}}$ (mmHg)	31.0 ± 5.0	30.7 ± 4.2	28.7 ± 2.9	30.0 ± 2.0
HRpeak (b min−1)	119 ± 18	132 ± 19	125 ± 19	118 ± 13
$S_{\mathrm{a}{\mathrm{O}}_2}$ (%)	98.6 ± 1.3	98.3 ± 1.3	98.2 ± 1.4	98.5 ± 1.4
RPE‐dyspnoea scores (0–10)	2.8 ± 1.8	3.2 ± 1.7	3.4 ± 2.0	2.1 ± 1.6
RPE‐leg effort scores (0–10)	9.1 ± 1.4	9.6 ± 0.9	9.9 ± 0.3	9.5 ± 1.2

Data are the mean ± SD. BDC, baseline data collection; N‐BR, normoxic bed rest; H‐BR, hypoxic bed rest; H‐AMB, hypoxic ambulatory confinement.

${\dot{V}}_{\mathrm{E}}$, pulmonary ventilation, V _T, tidal volume; fR, respiratory frequency; ${\dot{V}}_{{\mathrm{O}}_2}$, O₂ uptake; BM, body mass; TM: thigh muscle mass; ${\dot{V}}_{\mathrm{C}{\mathrm{O}}_2}$, CO₂ output; R, gas‐exchange ratio, $P_{\mathrm{ET}{\mathrm{O}}_2}$, O₂ end‐tidal pressure; $P_{\mathrm{ETC}{\mathrm{O}}_2}$, CO₂ end‐tidal pressure; HR, heart rate; $S_{\mathrm{a}{\mathrm{O}}_2}$: arterial blood O₂ saturation; RPE, ratings of perceived exertion. ^*Significantly different from BDC (P < 0.05).