Table 3: Changes in Oxygen uptake ( V ˙ O 2 ), Carbon dioxide output ( V ˙ C O 2 ), and Respiratory exchange ratio (RER) at rest and during incremental exercise at the three CO2 levels

Air (n=8) 3% CO2 (n=8) 6% CO2 (n=7)
V ˙ O 2max ( ml/min/kg ) 46.6 ± 4.0 45.7 ± 6.1 42.6 ± 4.7
V ˙ O 2 (ml/min) Rest 271.8 ± 57.9 284.6 ± 23.0 348.6 ± 148.8
30% V ˙ O 2max 879.8 ± 180.9 873.6 ± 215.6 861.1 ± 155.4
45% V ˙ O 2max 1295.6 ± 301.8 1267.0 ± 317.9 1248.0 ± 182.1
60% V ˙ O 2max 1687.8 ± 259.9 1741.0 ± 300.9 1605.6 ± 220.6
80% V ˙ O 2max 2376.1 ± 405.8 2410.9 ± 434.6 2106.4 ± 373.6
90% V ˙ O 2max 2714.9 ± 459.4 2723.4 ± 521.3 2423.7 ± 389.5
Max 3002.4 ± 532.8 2940.5 ± 604.9 2719.0 ± 447.4
V ˙ C O 2 (ml/min) Rest 241.8 ± 44.4 218.9 ± 27.7 162.9 ± 37.6
30% V ˙ O 2max 729.3 ± 169.0 646.8 ± 167.3 563.9 ± 164.4
45% V ˙ O 2max 1233.1 ± 337.7 1052.4 ± 306.1 964.3 ± 175.9
60% V ˙ O 2max 1733.0 ± 298.4 1586.0 ± 299.7 1346.7 ± 201.2
80% V ˙ O 2max 2645.3 ± 491.6 2351.3 ± 404.6 1925.7 ± 408.9 *†
90% V ˙ O 2max 3101.8 ± 493.0 2707.9 ± 565.8* 2339.6 ± 436.6*
Max 3589.6 ± 562.5 2973.3 ± 765.0* 2614.3 ± 629.2*
RER Rest 0.90 ± 0.11 0.77 ± 0.09* 0.55 ± 0.16*†
30% V ˙ O 2max 0.83 ± 0.07 0.74 ± 0.08* 0.65 ± 0.08*†
45% V ˙ O 2max 0.94 ± 0.07 0.83 ± 0.07* 0.77 ± 0.05*
60% V ˙ O 2max 1.03 ± 0.05 0.91 ± 0.05* 0.84 ± 0.05*
80% V ˙ O 2max 1.11 ± 0.04 0.98 ± 0.07* 0.92 ± 0.10*
90% V ˙ O 2max 1.15 ± 0.05 0.99 ± 0.08* 0.97 ± 0.08*
Max 1.20 ± 0.05 1.01 ± 0.14* 0.95 ± 0.13*

Values are means ± SD. *P<0.05 vs Air. P<0.05 vs 3% CO2 .