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

Abstract

The purpose of this study was to compare oxygen uptake estimated from submaximal Åstrand tests (VO₂est) with measured peak oxygen uptake (VO₂peak) 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. VO₂peak and HRpeak were measured. VO₂est was based on HR at constant load. HRest was calculated by the formula 220 − age. The mean± SD of VO₂est 2.05 ± 0.39 l/min (20 ± 5 ml/kg/min) was lower than VO₂peak 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 Åstrand test and of HR by the formula 220 − age had low validity in obese subjects. Consequently, direct measurements of HRpeak and VO₂peak are recommended for accurate prediction of obese individual's exercise capacity.

Key words::

• Åstrand test
• heart rate
• oxygen uptake
• VO₂max

Acknowledgements

This study was performed at Centre of Muscle Research in Copenhagen (CMRC) and we are grateful for all technical and medical assistance from the staff members involved.

Declaration of interest: This study was financially supported by, the Danish Health and Medicines Authority in Copenhagen, Copenhagen and Ballerup municipality.