Physical activity is independently related to aerobic capacity in cystic fibrosis

It is unclear whether a relationship between physical activity (PA) and maximal oxygen uptake (V'O-2,max) exists in cystic fibrosis (CF) and, if so, whether the relationship reflects a direct effect or is mediated by the effects of confounding variables, such as pulmonary or muscle function. The objective of the present study was to determine the relationship between PA and V'O-2,max in CF while adjusting for possible influences of confounding factors. In total, 36 female and 35 male patients with CF from Germany and Switzerland (aged 12-40 yrs, forced expiratory volume in one second (FEV1) 25-107% predicted) were studied. A Wingate test was employed to measure muscle power. PA was monitored for 7 days and expressed in two ways: 1) average daily accelerometer count (ADAC) and 2) time spent in moderate-to-vigorous PA (MVPA). V'O-2,max was determined during an incremental cycle exercise test to volitional fatigue. PA was positively related to V'O-2,max. In a multiple linear regression analysis, height, sex, FEV1, muscle power and ADAC (additionally explained variance 2.5%) or time spent in MVPA (additionally explained variance 3.7%) were identified as independent predictors of V'O-2,max. In conclusion, high levels of physical activity in addition to good muscular and pulmonary functions are associated with a high aerobic capacity in cystic fibrosis.