Fig. 2. (A) Maximum 1 min average _O2 during voluntary exercise on the wheels (_O2max,W), forced exercise on the treadmill (_O2max,T), and acute cold exposure in heliox (_O2max,H), in 47 females from S and C lines. (B) Maximum running speeds obtained on the treadmill (Spd_Max,T) and on the wheel (Spd_Max,W) for these same individuals. Values for oxygen consumption are adjusted means from SAS PROC MIXED for a female of 25.3 g; values for speed are not adjusted for mass (see text). Asterisks indicate significant differences between S and C lines (P<0.05, Table 3). Vertical bars indicate ± 1 S.E.M.