Effects of a large carbohydrate load on walking performance in chronic air-flow obstruction

The purpose of this study was to determine whether a single large liquid carbohydrate (CHO) load (920 calories) affects walking performance in patients with chronic air-flow obstruction (CAO). Walking performance was measured using the 12-min walking test. Fifteen patients with stable CAO (FEV1, 1.30 +/- 0.41 L; FVC, 3.26 +/- 0.46 L) underwent 12-min walking tests 40 min after ingestion of either CHO or placebo on consecutive days in randomized double-blind fashion. Three practice walks were performed on a preliminary day in order to eliminate learning effects. Resting measurements of ventilation (VE) and carbon dioxide output (VCO2) were obtained prior to each walking test. Carbohydrate significantly increased both VCO2 (from 0.288 +/- 0.060 to 0.372 +/- 0.057 L/min, p less than 0.001) and VE (from 15.2 +/- 3.5 to 18.5 +/- 3.1 L/min, p less than 0.001) at rest. The total 12-minute walking distance decreased from 894 +/- 199 to 847 +/- 191 m following CHO (p less than 0.005). This distance decreased in 14 of the 15 study patients. The decrease in walking distance ranged from 1.5 to 168 m (0.2 to 15.2%). From this study we conclude that a large liquid carbohydrate load adversely affects walking performance in patients with CAO. This potential impairment of functional capacity should be considered when caloric intake is increased in attempts to improve nutritional status in this patient population.