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Peripheral muscle weakness and exercise capacity in children with cystic fibrosis
K de Meer1, V A Gulmans, J van Der Laag
1Departments of Gastroenterology, Physiotherapy, and Respiratory Diseases, University Children's Hospital "Het Wilhelmina Kinderziekenhuis", Utrecht, The Netherlands. kdemeer@azu.nl
Insights
Children with cystic fibrosis (CF) experience reduced muscle force, impacting exercise capacity even without severe lung or nutritional issues. This finding highlights muscle weakness as a key factor in CF exercise intolerance.
Area of Science:
- Pediatric Pulmonology
- Exercise Physiology
- Metabolic Disorders
Background:
- Exercise intolerance is a common issue in cystic fibrosis (CF), often linked to poor nutrition and lung function.
- The specific role of muscle strength and body composition in CF-related exercise limitations requires further investigation.
Purpose of the Study:
- To investigate the relationship between muscle force, fat-free mass (FFM), and exercise intolerance in children with CF.
- To compare these parameters between children with mild and moderate CF symptoms and healthy controls.
Main Methods:
- Study included 15 children with moderate CF, 13 with mild CF, and 13 healthy controls.
- Assessed maximal workload (Wmax), maximal oxygen uptake (V O2max), maximal peripheral muscle force, and FFM.
- Compared physiological and performance metrics across the three groups.
Main Results:
- Children with mild CF showed reduced Wmax per kg FFM and diminished maximal muscle force compared to controls.
- Patients with moderate CF had lower FFM, muscle force, and exercise tolerance than both mild CF and control groups.
- Elevated oxygen cost of exercise was observed in both CF groups; muscle force strongly correlated with Wmax.
Conclusions:
- Decreased muscle force is a significant factor contributing to reduced exercise capacity in children with CF.
- This muscle weakness impacts exercise tolerance even when pulmonary function and nutritional status are not severely compromised.
- Muscle strength should be considered in managing exercise limitations in pediatric CF patients.
Abstract:
Exercise intolerance in cystic fibrosis (CF) is attributed to diminished nutritional and pulmonary function. We studied the pathophysiology of such intolerance in relation to muscle force and fat-free mass (FFM), in 15 children with moderately severe symptoms of CF (FEV1 < 80% predicted and/or weight for age < -1 SD of reference median), 13 children with mild symptoms of CF (FEV1 and weight above these thresholds), and 13 healthy controls. Cycle maximal workload (Wmax) and V O2max were assessed. Maximal peripheral muscle force was measured, and FFM was calculated from skinfolds. Patients with mild CF, as compared with matched controls, had lower values of Wmax per kilogram of FFM (3.9 +/- 0.5 versus 4.6 +/- 0.3 W/kg [mean +/- SD], respectively; difference = 0.7 [95% CI = 0.4 to 1.1]), and diminished maximal muscle force (2.7 +/- 0.4 kN versus 3.1 +/- 0.7 kN; difference = 0.44 [95% CI = 0.03 to 0.87]), but similar V O2max. Patients with moderate CF had lower FFM, muscle force, and exercise tolerance than did the other groups. Oxygen cost of work was elevated in both groups of CF patients. Muscle force showed a strong positive correlation with Wmax in patients and controls, with disproportionately lower regression slopes in the CF patients. In children with CF, muscle force is decreased and associated with diminished maximal work load, even in the absence of diminished pulmonary or nutritional status.