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.
Key Findings
Results
Percent predicted FEV₁ (ppFEV₁) was independently associated with intrinsic motivation in adults with cystic fibrosis after adjusting for CFTR modulator therapy status and sex.
Standardized regression coefficient β = .233, p < .001
The additional variance explained by ppFEV₁ beyond CFTR modulator status and sex was ΔR² = .054
Analysis conducted using hierarchical regression in a cross-sectional sample of N = 200 adults at a specialised CF centre
Motivational regulation was measured using the validated Behavioural Regulation Questionnaire-2 (BREQ-2)
Results
ppFEV₁ was independently associated with the Relative Autonomy Index (RAI), a composite measure of autonomous motivational regulation, in adults with CF.
Standardized regression coefficient β = .203, p = .004
The additional variance explained by ppFEV₁ for the RAI was ΔR² = .041
The RAI reflects the overall degree of autonomous versus controlled motivational regulation
Association remained after accounting for CFTR modulator therapy status and sex
Results
ppFEV₁ was independently associated with physical activity enjoyment (PACES total score) in adults with CF.
Standardized regression coefficient β = .201, p = .004
The additional variance explained by ppFEV₁ for PACES total score was ΔR² = .040
PA enjoyment was measured using the validated Physical Activity Enjoyment Scale (PACES)
Association persisted after controlling for CFTR modulator therapy status and sex
Results
The additional variance in motivational and enjoyment outcomes explained by ppFEV₁ beyond CFTR modulator status and sex was statistically significant but modest.
ΔR² values ranged from .040 to .054 across the three outcomes (intrinsic motivation, RAI, and PACES total score)
Authors described these associations as 'small, independent associations'
Multivariate general linear models (GLM), partial correlations, and hierarchical regression analyses were all utilised
The modest effect sizes indicate that lung function alone explains only a small portion of variance in psychological outcomes
Results
Neither CFTR modulator therapy status nor sex was significantly associated with autonomous motivational regulation or physical activity enjoyment outcomes.
This null finding held across all assessed motivational and enjoyment outcomes
CFTR modulators have transformed CF treatment but did not significantly predict motivational regulation in this sample
Cross-sectional design limits causal inference
Sample size was N = 200 adults at a specialised CF centre
Conclusions
The authors concluded that lung function should not be used as a proxy for motivational support needs in adults with CF.
Despite statistically significant associations, the small effect sizes mean ppFEV₁ cannot reliably predict individual motivational regulation or enjoyment
Authors recommend that motivational regulation and PA enjoyment should be assessed directly in adults with CF
The recommended approach is described as 'person-centred, SDT-informed support' (Self-Determination Theory)
The study design was cross-sectional, precluding causal conclusions
What This Means
This research suggests that lung function — specifically a measure called FEV₁ (how much air someone can forcefully breathe out in one second) — has a small but real relationship with how motivated people with cystic fibrosis (CF) feel about physical activity and how much they enjoy it. People with better lung function tended to report slightly higher levels of self-driven (autonomous) motivation and more enjoyment of physical activity. However, lung function only explained about 4–5% of the differences seen between individuals in these psychological measures, meaning most of what determines someone's motivation and enjoyment is not captured by their lung function test.
Importantly, the study found that whether or not someone was taking the newer CFTR modulator medications — drugs that have dramatically improved physical health for many CF patients — did not predict how motivated they were to exercise or how much they enjoyed it. Similarly, sex did not significantly predict these outcomes. The study involved 200 adults at a specialised CF centre and used validated questionnaires alongside clinical records.
This research suggests that healthcare providers working with adults with CF should not assume that knowing a patient's lung function tells them much about that patient's psychological relationship with physical activity. Even patients with relatively good lung function may struggle with motivation or enjoyment, and vice versa. The practical implication is that motivation and enjoyment of physical activity should be measured directly — through conversation or questionnaires — so that support can be tailored to each person's actual psychological needs rather than inferred from clinical test results.
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