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 (%V.O2max) 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 (V.O2) 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 (V.O2max/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 V.O2, 1.2±0.2 l · min−1(P<0.001), than normals. A majority experienced exertion and some experienced pain. Their V.O2max/kg, 21.2±5.0 ml · kg−1 · min−1, was less than for normals (P<0.0001). The mean % V.O2max during walking was 56%, which was higher than in normal subjects 36% (P<0.0001). Significant correlations between %V.O2max and V.O2max/kg (P<0.0001), heart rate during walking (P=0.0009) and age (P=0.0081), respectively, were found. CONCLUSION: Very low V.O2max/kg in obese women, rather than severe obesity per se, seems the most important factor to cause high %V.O2max 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.