V_E/VCO₂ slope in lean and overweight women and its relationship to lean leg mass

Ventilation/carbon dioxide production (V_E/VCO_2slope) is used clinically to determine cardiorespiratory fitness and morbidity in heart failure (HF). Previously, we demonstrated that lower lean leg mass is associated with high V_E/VCO_2slope during exercise in HF. In healthy individuals, we evaluated 1) whether V_E/VCO_2slope differed between lean and overweight women and 2) the relationship between lean leg mass and V_E/VCO_2slope in overweight sedentary (OWS), overweight trained (OWTR) and lean, trained (LTR) women.

Gas exchange and ventilation were collected during a treadmill peak oxygen uptake test (VO_2peak) in 40 women [26 OWS (29 ± 7 yrs., mean ± SD), 7 OWTR (33 ± 5 yrs) and 7 LTR (26 ± 6 yrs)]. Body composition was measured by dual X-ray absorptiometry.

VO_2peak was highest in LTR (46.6 ± 8 ml/kg/min) compared with OWTR (38.1 ± 4.9 ml/kg/min) and OWS women (25.3 ± 4.8 ml/kg/min, p < 0.05). Lean leg mass was highest in OWTR and lowest in LTR women (p < 0.05). V_E/VCO_2slope was similar between groups (p > 0.05). Higher lean leg mass was associated with lower V_E/VCO_2slope in overweight women (OWS + OWTR: r = -0.55, p < 0.001), contrasting with higher V_E/VCO_2slope in LTR women (r = 0.86, p < 0.001).

These findings suggest V_E/VCO_2slope may not differentiate between low and high cardiorespiratory fitness in healthy individuals and muscle mass may play a role in determining the V_E/VCO_2slope, independent of disease.