Exercise energy expenditure in extreme obesity: influence of ergometry type and weight loss.

Bicycle and treadmill exercise tests including oxygen uptake (VO2) and heart rate (HR) determination were carried out on a total of thirty patients with obesity, seventeen of whom were reinvestigated after weight loss. During both types of work VO2 for a given load was higher when compared to healthy controls. The increase of VO2 was more marked when cycling was performed in sitting position than in supine. The mechanical efficiency of sitting bicycle exercise averaged 17.8% and was negatively related to the percentage overweight; the slope of the VO2/load regression line was slightly less in comparison to the controls, while no such difference was found during treadmill walking. After weight reduction the VO2/load regression line was skifted downwards, the slopes being unchanged, thus the mechanical efficiency improved. This study not only confirms the observation of a low mechanical efficiency of obese subjects but also demonstrates that the change is quantitatively related to the overweight. The lowered efficiency was caused by body mechanical factors and there was no support for an abnormal muscular efficiency. Exercise tests should be combined with VO2 determination, if used to assess the circulatory capacity of obese subjects.