Mini-symposium: The Clinical Applications of Exercise Testing in ChildrenExercise and physical activity in children with cystic fibrosis
Introduction
Despite advances in clinical care, life expectancy in patients with cystic fibrosis (CF) remains shortened.1 It has been well documented that exercise capacity in this group is limited by lung function, peripheral skeletal muscle function2, nutritional status3, 4, 5 and the cardio-respiratory system's ability to meet the metabolic demands associated with exercise.4 Interestingly, the physiological consequences that have been observed in patients with CF are similar to the effects of de-conditioning including poor cardiovascular function, reduced muscle mass and impaired strength and power.6 Further, children with CF may be more physically inactive7 due to the burden of their chronic disease8 and therefore may be at risk of compounding the combined effects of chronic disease and physical inactivity.
The importance of exercise and habitual physical activity (HPA) for patients with chronic disease has been identified as an area of importance for health care providers, clinicians, researchers and most importantly, patients.6 Higher levels of exercise capacity have been reported to be important for survival in patients with CF. Several studies have demonstrated an association between aerobic capacity and clinical status in pediatric patients with CF. Nixon and co-workers reported a significant correlation between aerobic fitness (VO2) and survival9, which remained intact after adjustment for other predictor variables such as age, sex, lung function, nutritional status and bacterial colonization. The authors suggested that VO2peak could be used as an independent predictor of survival. This finding has been recently confirmed by Pianosi and colleagues10 who studied 28 patients 8-17 years over five years to determine the effect of declining lung function and VO2 as predictors of survival over the subsequent 7ā8 years. They found that patients with a VO2peak of greater than 45Ā mlĀ kgā1minā1 had an improved survival compared to those with a VO2peak less than 32Ā mlĀ kgā1minā1. Klijn and co-workers4 also reported a longitudinal relationship between changes in nutritional status, lung function, and VO2peak in children with CF. Fat-free mass (FFM), lung function, and VO2peak were assessed in 65 children with CF with a wide range of FEV1 at baseline and two years later. They concluded that longitudinal changes in lung function, and to a lesser extent nutritional status, were positively associated with functional changes in the aerobic capacity of children with CF.
Whereas āexerciseā infers structured activity, typically prescribed according to intensity and duration, HPA emphasizes activity which is incorporated into daily life, and encompasses a broader range of options for being active. Activity has been shown to specifically contribute to the health of patients with cystic fibrosis.11, 12, 13 Therefore the importance of exercise and HPA in patients with cystic fibrosis is critical and presents an opportunity for members of the health care team to implement regular activity recommendations as a routine part of clinical practice. This review summarizes a growing body of research on exercise and habitual physical activity in CF which provides a rationale and justification for their inclusion into routine clinical therapy for paediatric patients and for identification of areas for future research.
Section snippets
Challenges of exercise and activity participation for patients with cystic fibrosis
Despite the positive benefits of exercise and habitual physical activity in patients with chronic disease6, children with CF are not as active as their healthy peers.7 The specific challenges associated with single exercise sessions and participation in HPA must be considered by both clinicians and researchers if successful recommendations are to be made and evaluated in this population. Research documenting these challenges in CF is summarized in the following sections.
Physiological
Evidence of benefit of exercise training
The benefits of aerobic exercise training programs have been reported in the pediatric CF population. Several studies have demonstrated that patients with CF can improve aerobic capacity.26, 27 Recently, evidence for improvements in pulmonary function in relation to physical activity levels have been reported13, with girls participating in higher levels of activity demonstrating a significantly slower rate of decline in FEV1 compared to less active girls. Interestingly, comments from authors
Evidence of benefit of habitual physical activity
The conventional approach to addressing physical inactivity has been to prescribe an exercise training regimen based on the usual paradigms of frequency, intensity and duration with the goal to increase specific measures of athletic performance such as aerobic capacity or muscular strength. However, once the training period is complete, the benefits are often lost as patients are reluctant to continue on their own. Supervision of a training regimen whether in-house or within the community is
Conclusions
Similar to the healthy population, āexercise training programsā such as those aimed at improving aerobic fitness or muscular strength and endurance, are effective in children with cystic fibrosis. Habitual physical activity has been shown to decrease the rate of decline of FEV1 in girls and is an independent predictor of long term survival. Exercise training and/or habitual physical activity should become an integral part of the treatment regimen for cystic fibrosis.
In order to improve and
Key points
- 1.
Exercise and physical activity are important for patients with cystic fibrosis.
- 2.
There is now a body of research that has described the exercise limitations in patients with CF, and these results can be used to justify and guide the implementation of āexercise as medicineā programs in CF clinics.
- 3.
Significant resources for physicians who are interested in implementing exercise as therapy are available at www.exerciseismedicine.org.
Acknowledgements
We are grateful to the Canadian Cystic Fibrosis Foundation and the Irwin Foundation at the Hospital for Sick Children, Toronto for funding.
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