Quantification of cardiorespiratory fitness: obese vs. normal weight individuals

VO 2peak (L/min) increases with body wt, but decreases if adjusted for body mass (ml/min/kg). Thus, it is unclear how to compare VO 2peak or cardiorespiratory fitness (CRF) among individuals of different sizes. To investigate, we compared VO 2peak in absolute terms, and relative terms (%predicted) using two prediction methods: #1) based on age, gender, and predicted weight ( Riddle etal, 1980); #2) based on age, gender, predicted weight, and a correction factor (actual wt‐predicted wt*6ml/kg) ( Wasserman etal , 2004). 19 non‐obese (NO; 8W) and 66 obese (OB; 26W) participated. Subjects underwent underwater weighing and incremental cycling to exhaustion. Data were analyzed by independent t‐test. CRF was equal in NO and OB (2.35 ± 0.80 vs. 2.39 ± 0.68 L min 1 , respectively), but decreased in OB (p<0.05) in ml/min / kg (34 ± 8 vs. 22 ± 5), and in ml/min/LBM (42 ± 9 vs. 37 ± 6). Using Method #1, CRF was equal in NO and OB (91 ± 17 vs. 94 ± 15 %predicted), but using Method #2, CRF was decreased (p<0.05) in OB (94 ± 15 vs. 87 ± 11 %predicted). We further examined Method #1 by adding the correction factor in OB and observed CRF to be equal in NO and OB (90 ± 16 vs. 86 ± 14 %predicted). Traditional techniques for assessing CRF are not applicable when comparing NO and OB. This includes LBM. When CRF is evaluated using %predicted, the difference in CRF can vary depending on which prediction equations are selected. Funding: King & Cain Foundations, ALA, AHA, & THPD.