Is walking for exercise too exhausting for obese women?

Abstract

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.