Is walking for exercise too exhausting for obese women?

OBJECTIVES

As exhaustion and pain during walking seem to be common problems among obese women, we decided to analyse the relative oxygen cost (% VO2max) in obese women during level walking.

SUBJECTS: Fifty-seven obese female outpatients, 44.1 +/- 10.7 y, BMI 37.1 +/- 3.4 kg.m-2.

METHODS

Walking tests at a self-selected, comfortable speed were performed indoors. Speed was measured with a speedometer, oxygen consumption (VO2) with the argon-dilution method and oxygen cost was estimated. Heart rate was measured; perceived exertion and pain were assessed with Borg's Category Ratio scale, CR10. Maximum oxygen uptake (VO2max/kg) was predicted from a submaximum bicycle ergometry test.

RESULTS

The women walked more slowly, 70.9 +/- 5.6 m.min-1 (P < 0.0001), and had higher VO2, 1.2 +/- 0.2 l.min-1 (P < 0.001), than normals. A majority experienced exertion and some experienced pain. Their VO2max/kg, 21.2 +/- 5.0 ml.kg-1.min-1, was less than for normals (P < 0.0001). The mean % VO2max during walking was 56%, which was higher than in normal subjects 36% (P < 0.0001). Significant correlations between % VO2max and VO2max/kg (P < 0.0001), heart rate during walking (P = 0.0009) and age (P = 0.0081), respectively, were found.

CONCLUSION

Very low VO2max/kg in obese women, rather than severe obesity per se, seems the most important factor to cause high % VO2max during walking. This might explain why many obese women perceive the exertion to be excessive and cannot follow the advice of their clinicians to exercise through long and brisk walks.