Relationships among nutritional status and skeletal and respiratory muscle function in cystic fibrosis: does early dietary supplementation make a difference?

Relationships among nutritional status and skeletal and respiratory muscle function were examined in 16 children with cystic fibrosis (CF) and mild lung disease (FEV1 95 +/- 16% predicted). Subjects were randomly assigned to receive (or not) noninvasive nutritional supplementation at 25% of normal energy recommendations for 6 mo. Skeletal muscle strength and power were similar to those of healthy children as were respiratory muscle strength and endurance. Stepwise-regression analysis indicated that changes in skeletal muscle strength and energy intake correlated significantly with growth [weight (kg) = 1.90 - 0.60 (Tanner Stage) + 0.49 (maximum voluntary strength (Nm) + 0.03 (energy intake, % RNI), r = 0.76, P < 0.05], though body composition, protein biochemistry, muscle power, respiratory muscle strength, and use of dietary supplements did not. Thus, changes in skeletal muscle strength may be a functional index of changes in nutritional status in CF. Dietary supplementation per se was not associated with functional improvement.