Validation of a submaximal versus a maximal exercise test in obese individuals

The purpose of this study was to compare oxygen uptake estimated from submaximal A strand tests (VO(2)est) with measured peak oxygen uptake (VO(2)peak) from maximal tests, and to compare estimated maximal HR (HRest) with measured HRpeak in obese subjects. Seventy obese subjects performed a maximal exercise test starting with a 4-min period of constant load. VO(2)peak and HRpeak were measured. VO(2)est was based on HR at constant load. HRest was calculated by the formula 220 - age. The mean +/- SD of VO(2)est 2.05 +/- 0.39 l/min (20 +/- 5 ml/kg/min) was lower than VO(2)peak 2.42 +/- 0.57 l/min (17 +/- 4 ml/kg/min) (p < 0.001, p < 0.001, respectively). The mean difference +/- 2SD was - 0.4 +/- 1.22 l/min (- 3 +/- 10 ml/kg/min) with an uneven distribution of the individual variation. The correlation between the methods was low (r = 0.24, r = 0.38 respectively). The mean +/- SD of HRest 176 +/- 10 bpm was higher than the HRpeak 161 +/- 17 bpm (p < 0.001). The mean difference +/- 2SD was 15 +/- 31.3 bpm with an uneven distribution of the individual variation. The correlation between the methods was low (r = 0.41). The main findings of this study were that estimation of VO2 from the A strand test and of HR by the formula 220 - age had low validity in obese subjects. Consequently, direct measurements of HRpeak and VO(2)peak are recommended for accurate prediction of obese individual's exercise capacity.