Moving beyond treatment: pulmonary function, autonomous motivation, and physical activity enjoyment in adults with cystic fibrosis

Abstract Background Physical activity (PA) and structured exercise are established cornerstones of cystic fibrosis (CF) management. While CFTR modulators have transformed treatment, the psychological factors affecting sustained PA adherence, particularly motivational regulation and PA enjoyment, require further investigation. This study aimed to determine whether percent predicted forced expiratory volume in one second (ppFEV₁) is independently associated with autonomous motivation and PA enjoyment in adults with CF, after adjusting for CFTR modulator therapy status and sex. Methods A cross-sectional study was conducted at a specialised CF centre ( N = 200). Participants completed validated questionnaires assessing motivational regulation (Behavioural Regulation Questionnaire-2, BREQ-2) and PA enjoyment (Physical Activity Enjoyment Scale, PACES). Clinical data, including the ppFEV₁, were obtained from medical records. Multivariate general linear models (GLM), partial correlations, and hierarchical regression analyses were utilised. Results Cross-sectional analyses showed that ppFEV₁ was independently associated with intrinsic motivation (β = .233, p < .001), the relative autonomy index (RAI) (β = .203, p = .004) and the PACES total score (β = .201, p = .004). After CFTR modulator therapy status and sex were accounted for, the additional variance explained by the ppFEV₁ was statistically significant but modest (ΔR 2 = .054, .041, and .040, respectively). Neither the CFTR modulator therapy status nor sex was significantly associated with the assessed motivational or enjoyment outcomes. Conclusions Although ppFEV₁ showed small, independent associations with autonomous motivational regulation and PA enjoyment in adults with CF, lung function should not be used as a proxy for motivational support needs. To provide person-centred, SDT-informed support that encourages sustained participation in PA, the motivational regulation and enjoyment of PA should be assessed directly in adults with CF.