Key result
Liver transplant recipients unwilling to participate in an exercise trial had lower education and income, lived farther from the study site, and engaged in significantly fewer daily steps and less moderate-to-vigorous physical activity compared to willing participants.
Why the study?
Understanding participation barriers in exercise trials is critical to increase sample representativeness, mitigate selection bias, and achieve target sample sizes.
What are the barriers, motivators, and physical activity differences between liver transplant recipients willing versus unwilling to participate in an exercise RCT?
Cross-Sectional (n=104)
No
What are the barriers, motivators, and physical activity differences between liver transplant recipients willing versus unwilling to participate in an exercise RCT?
Absolute Event Rate: 4472% vs 2990%
p-value: p=0.01
Sociodemographic factors and baseline physical activity levels significantly influence the willingness of liver transplant recipients to participate in exercise trials, highlighting potential selection bias.
May under-enroll socioeconomically disadvantaged and inactive liver transplant recipients; confirms selection bias and challenges broad generalizability of exercise trial results.
BACKGROUND: Understanding barriers to participate in exercise intervention studies is critical for guiding approaches to increase sample representativeness, to mitigate selection bias, and to achieve the required sample size for study purposes. This study compared physical activity levels and exercise-related perceptions, including barriers and facilitators, between liver transplant recipients who were willing versus not-willing to engage in an exercise intervention randomised controlled trial (RCT). METHODS: A comparative cross-sectional study was conducted using baseline data of the PHOENIX-Liver trial, a RCT evaluating a 6-month home-based exercise intervention followed by a physical activity maintenance program. Two informed consents were obtained from eligible liver transplant recipients (3-5 months post-transplant; >18 years) either willing (n = 64) or not willing (n = 46) to participate. Clinical and sociodemographic characteristics were collected from electronic medical records and questionnaires. Physical activity was assessed objectively (accelerometry) and subjectively (Physical Activity Vital Sign Questionnaire). Exercise-related barriers and facilitators were measured using the Motivators and Barriers Questionnaire. RESULTS: 42% of 110 eligible individuals declined participation, most often due to time constraints (40%), transportation challenges (25%), and lack of motivation (15%). Non-participants were significantly more likely to have lower education (p = 0.009), lower income (p = 0.004), and live farther from the study site (p = 0.004). Self-reported physical activity levels did not differ between groups, but accelerometry showed that non-participants spend less time in moderate-to-vigorous physical activity (p = 0.05) and took fewer daily steps (p = 0.01). Multivariate logistic regression showed trends for greater distance from centre (p = 0.056), lower education (p = 0.082), and lack of motivation/time (p = 0.071) with unwillingness to participate. High income was independently associated with meeting WHO physical activity guidelines (p = 0.049). CONCLUSION: A substantial proportion of eligible individuals declined participation. Some sociodemographic and behavioural barriers point to potential selection bias. Addressing these through tailored study designs could enhance engagement, improve representativeness and support the recruitment of representative patient populations in future exercise interventions. CLINICAL TRIAL REGISTRATION NUMBER: NCT06302205 (trial registration date: 06/12/2023).
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Leunis et al. (2025) conducted a cross-sectional in Liver transplant recipients (n=104). Willingness to participate in an exercise RCT vs. Unwillingness to participate was evaluated on Objectively measured daily step count (p=0.01). Liver transplant recipients unwilling to participate in an exercise trial had lower education and income, lived farther from the study site, and engaged in significantly fewer daily steps and less moderate-to-vigorous physical activity compared to willing participants.
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