Spiroergometric assessment of cardiorespiratory fitness in subjects with severe obesity: A challenge of reference

BACKGROUND AND AIMS: Severe obesity is associated with poor physical performance but objective data are scarce.

METHODS AND RESULTS: Bicycle spiroergometry data with focus on peak oxygen uptake (V˙O2,peak) and workload (Wpeak) from 476 subjects with severe obesity (BMI ≥ 35.0 kg/m2; 70% women) were analysed. In a first step, V˙O2,peak values were compared with reference values calculated upon different formulas (Wassermann; Riddle). Thereafter, multivariate regression analyses were performed to identify determinants of cardiorespiratory fitness. Cardiorespiratory fitness reference classes for V˙O2,peak and Wpeak were established by stratifying the sample upon identified determinants. Absolute V˙O2,peak (1.87 ± 0.47 vs. 2.40 ± 0.59 l/min) and Wpeak (131 ± 26 vs. 168 ± 44 W) were lower in women than men (both p<0.001). Same pattern was found for relative V˙O2,peak and Wpeak, respectively (both p < 0.05). In women, measured V˙O2,peak was lower than predicted by Wasserman (p < 0.001) but not by Riddle (p = 0.961). In men, V˙O2,peak was lower than calculated by both Wasserman and Riddle formulas (both p ≤ 0.003). Multivariate analyses revealed height and age to be the main determinants of cardiorespiratory fitness in both sexes. Subsequent statistical analyses of calculated reference fitness classes revealed that V˙O2,peak and Wpeak differed between the age- and height-defined groups in both sexes (all p < 0.001).

CONCLUSION: Data indicate that the evaluation of cardiorespiratory fitness in subjects with severe obesity is largely biased by selected references values for comparison. Our newly established reference fitness classes upon height and age might be helpful in the clinical context when dealing with obese patients.