Physical fitness and quality of life in children with cystic fibrosis

Abstract

In chapter 1 an introduction on general characteristics of cystic fibrosis (CF) is provided, followed by an overview of literature on exercise studies in children with CF. This literature review showed that children with CF are able to improve their aerobic capacity with short-term training programs but not their pulmonary function. Possibly, long-term adherence to exercise training is necessary to improve clinical prognosis. Furthermore, an outline for anaerobic training in children with CF is presented. Improvement of anaerobic performance is thought to positively influence participation in daily activities as well as sport activities, which may eventually lead to improvements of health-related quality of life. Chapter 2 describes the long-term relationship between changes in peak aerobic performance (VO2peak), pulmonary function and fat-free mass (FFM) in sixty-five children with mild to moderate CF. Over the two-year study period an increase was found for absolute values of FFM, pulmonary function and VO2peak while a decrease was found for predicted values of pulmonary function and VO2peak. It was concluded that changes in VO2peak are associated with changes in pulmonary function and to a lesser degree with changes in fat-free mass. In chapter 3 the determinants of anaerobic performance are described in thirty-nine children with mild to moderate CF. FFM was found the most important determinant of anaerobic performance. In addition, pulmonary function also contributed significantly to anaerobic performance when FFM was controlled for. An interesting outcome was that subjects with moderate pulmonary dysfunction had higher anaerobic power output per FFM than subjects with mild pulmonary dysfunction. It was concluded that anaerobic energy metabolism may be enhanced with progression of pulmonary disease. Chapter 4 describes the validation process of the Cystic Fibrosis Questionnaire (CFQ) for children with CF in the age from 6 to 13 years (CFQ-C) and their parents (CFQ-P). Internal consistency was acceptable for most domains of the CFQ-C and the CFQ-P. Test-retest reliability was high for all domains and the construct validity of both CFQ questionnaires was good, with moderate to strong correlations between physically oriented CFQ-domains and pulmonary function, nutritional status, inflammation and physical performance. The CFQ-C and the CFQ-P were able to differentiate between two levels of disease severity and the convergence between the two measures was confirmed by strong correlations on observable domains. Chapter 5 describes the validation process of the CFQ for adolescents and adults (CFQ-14+). Internal consistency was acceptable for most domains of the CFQ-14+ and the test-retest reliability was high for all domain scores. Several domains of the CFQ-14+ were able to differentiate between individuals with varying disease severity and between nourished and malnourished patients. Construct validity of the questionnaire was fair, with moderate to strong correlation between physically orientated domains and pulmonary function. From the results of chapter 4 and 5, it was concluded that the CFQ questionnaires can be used to monitor the health status and quality of life of patients with CF from the age of 6 years throughout adulthood. Chapter 6 describes the effects of our anaerobic training program on aerobic and anaerobic exercise performance, pulmonary function, fat-free mass, peripheral muscle force and health-related quality of life. The TG trained two days per week for 12 weeks, with each session lasting 30-45 minutes. The training program consisted of anaerobic activities, lasting 20 to 30 seconds. The control subjects were asked not to change their normal daily activities. The outcome parameters were re-evaluated at the end of the training program and again after a 12-week follow-up period. In the training group significant positive effects were found for aerobic and anaerobic performance and for health-related quality of life. The improvements in anaerobic performance and HRQOL were maintained through a 12-week follow-up period. It was concluded that anaerobic training could be an important component of the physical rehabilitation program of children with CF.