Adverse Effect of Additional Weight on Exercise Against Gravity in Patients With Chronic Obstructive Airways Disease

Abstract

The effects of an acute, artificially simulated increase in body weight on exercise performance were examined in 14 patients of normal weight (mean (SD) body mass index 22.3 (2.7)), age 61 (8) years) with chronic obstructive airways disease (FEV1 1.2 (0.5) 1; vital capacity (VC) 2.9 (0.6) 1), and in six normal subjects with similar age and sex distribution. The patients performed a six minute walking test and a symptom limited step climbing test both with and without an additional 10 kg weight (two leaded aprons). The normal subjects performed a step test with and without the additional weight. Ventilation (VE) and oxygen consumption (VO2) were measured during step climbing. Resting spirometric values were not altered by the additional weight. In the patients the median number of steps climbed fell from 67.5 when they were unweighted to 44.5 when they were weighted. Mean VE and VO2 were increased during weighted step climbing by 14% and 13% but the maximum levels of VE and VO2 achieved were similar during unweighted and weighted exercise (VE 36.8 (8.6) and 37.3 (10.2) 1 min-1, VO2 1.35 (0.3) and 1.41 (0.4) 1 min-1 respectively). The normal subjects were readily able to complete 150 steps both with and without the additional weight. In the patients the six minute walking distance fell only slightly with the extra weight, from 554 (SD 61) to 540 (62) m. A subsidiary study was carried out in six healthy younger subjects in which VE and VO2 were measured during a 5.6 km/h six minute treadmill walk at zero incline. The additional weight did not alter VE or VO2 during exercise. In conclusion, a small acute increase in body weight substantially worsened the already reduced uphill exercise performance in patients with chronic obstructive airways disease because of its effect on ventilation and oxygen consumption. These results suggest that modest weight loss might benefit patients with chronic obstructive airways disease even though they may be only slightly above their ideal body weight.