Abstract and Introduction
Purpose: The purpose of our study was to assess the effects of an 8-wk intrahospital combined circuit weight and aerobic training program performed by children with cystic fibrosis (of low–moderate severity and stable clinical condition) on the following outcomes: cardiorespiratory fitness (V˙O2peak) and muscle strength (five-repetition maximum (5RM) bench press, 5RM leg press, and 5RM seated row) (primary outcomes) and pulmonary function (forced vital capacity, forced expiratory volume in 1 s), weight, body composition, functional mobility (Timed Up and Down Stairs and 3-m Timed Up and Go tests), and quality of life (secondary outcomes). We also determined the effects of a detraining period (4 wk) on the aforementioned outcomes.
Methods: We performed a randomized controlled trial design. Eleven participants in each group (controls: 7 boys, age = 11 ± 3 yr, body mass index = 17.2 ± 0.8 kgöm−2 (mean ± SEM); intervention: 6 boys, age = 10 ± 2 yr, body mass index = 18.4 ± 1.0 kgöm−2) started the study.
Results: Adherence to training averaged 95.1% ± 7.4%. We observed a significant group × time interaction effect (P = 0.036) for V˙O2peak. In the intervention group, V˙O2peak significantly increased with training by 3.9 mLökg−1Imin−1 (95% confidence interval = 1.8–6.1 mLökg−1Imin−1, P = 0.002), whereas it decreased during the detraining period (−3.4 mLökg−1Imin−1, 95% confidence interval = −5.7 to −1.7 mLökg−1Imin−1, P = 0.001). In contrast, no significant changes were observed during the study period within the control group. Although significant improvements were also observed after training for all 5RM strength tests (P < 0.001 for the interaction effect), the training improvements were not significantly decreased after the detraining period in the intervention group (all P > 0.1 for after training vs detraining). We found no significant training benefits in any of the secondary outcomes.
Conclusions: A short-term combined circuit weight and aerobic training program performed in a hospital setting induces significant benefits in the cardiorespiratory fitness and muscle strength of children with cystic fibrosis.
Cystic fibrosis (CF) is a progressive hereditary disease, affecting 1 of 2500 Caucasian newborns. Because of a defect in the CF transmembrane conductance regulator gene, excess mucous is produced in the lungs, liver, pancreas, and reproductive organs; pulmonary function is impaired; absorption of nutrients is suboptimal; and bacterial infections frequently occur. In children with CF, exercise capacity and cardiorespiratory fitness are often limited because of several reasons: obstruction of bronchioles impairs gas exchange, respiratory muscles are weakened, and lung tissue is inflamed, all of which decrease pulmonary function. Heart function can be altered mainly by an increase in the right ventricular afterload imposed by hypoxic vasoconstriction and increased pulmonary vascular resistance. Peripheral muscles are also affected because of systemic inflammation, oxidative stress, malnutrition, and lack of vigorous physical activity. Given the above, it is not surprising that pulmonary function, expressed as forced expiratory volume in 1 s (FEV1) or forced vital capacity (FVC), and cardiorespiratory fitness, expressed as peak oxygen uptake (V˙O2peak), are strong indicators of survival among patients with CF.
Several studies have reported the effects of exercise interventions (using aerobic or resistance exercises) on health- and exercise-related phenotypes in patients with CF, including five randomized controlled trials (RCTs)[12,15,24,31,33] (for reviews, see Bradley et al. and van Doorn). Selvadurai et al. compared the effects of aerobic and resistance training interventions, i.e., five weekly sessions of aerobic (treadmill/cycle ergometry) versus five weekly sessions of resistance exercises (upper and lower limb machine exercises) performed by children with CF (age 8–16 yr) during hospitalization for intercurrent pulmonary infection (mean duration = 18–19 d). Compared with resistance training, the aerobic program resulted in greater gains in V˙O2peak, physical activity levels, and quality of life (QoL), whereas the former intervention resulted in greater increases in children's weight, lung function, and leg muscle strength. The results of their study suggest an exercise program composed of both aerobic and resistance training may positively affect more physiological factors negatively affected by CF than either training type alone. However, no previous RCT has assessed the effects of a combined intrahospital program, i.e., including both resistance (weight lifting) and endurance exercises, on the functional capacity of children with CF. We recently built an intrahospital pediatric gymnasium (including weight training machines especially designed for the body size of children and cycle ergometers). This provides an ideal setting for intrahospital exercise interventions in chronically diseased children and adolescents, as recently shown.[6,29]
The main purpose of the current RCT was to assess the effects of an 8-wk combined circuit weight and aerobic training program on pulmonary function (FVC, FEV1), cardiorespiratory fitness (V˙O2peak), dynamic muscle strength, weight, body composition, functional mobility, and QoL in children with CF. Concurrent training of both aerobic and strength abilities was chosen as the training type to enhance both V˙O2peak and strength, both of which are negatively affected by CF. Circuit weight training was chosen as the resistance training type because it has been shown to significantly increase both muscle strength and V˙O2peak. We also determined the effects of a detraining period on the aforementioned outcomes. We hypothesized that the combined training program would result in increases in the aforementioned variables in children with CF compared with a control group performing no physical training.
Med Sci Sports Exerc. 2012;44(1):2-11. © 2012 American College of Sports Medicine