Evaluating the Scalability of the ProMuscle Intervention for Community-Dwelling Older Adults: A Mixed Methods Study

Background The global population is ageing, leading to an increase of older adults with sarcopenia, a condition associated with reduced quality of life and higher healthcare costs. ProMuscle, a 12-week intervention combining strength training and protein intake, has been shown to effectively improve physical functioning in older adults. Although ProMuscle has demonstrated promising results on a smaller scale, further scale up requires adapted strategies to address emerging challenges. This study aims to assess the scalability of ProMuscle, systematically guided by the Intervention Scalability Assessment Tool (ISAT). Methods A mixed-methods approach was used, combining a review of documents, interviews (n = 8), online surveys (n = 49), and consensus focus groups (n = 2), all involving key stakeholders. Each of the ISAT domains - the problem, the intervention, strategic and political context, effectiveness, costs, fidelity and adaptation, reach and acceptability, delivery setting and workforce, implementation infrastructure, and sustainability – were addressed during data collection. Findings of the scalability assessment were displayed for each of the ISAT domains in a radar plot. Results The ISAT indicates that ProMuscle holds strong potential for scale up. The demonstrated effectiveness, the relevance of sarcopenia prevention, its alignment with broader health priorities, and its potential to reduce healthcare costs were supported by both scientific evidence and stakeholder consensus. However, key challenges were identified in the strategic and political context and implementation infrastructure, which must be addressed before further scale up. Structural barriers, such as the lack of sustainable funding, limited awareness, and lack of prioritization of sarcopenia among policymakers and healthcare professionals were described as significant challenges. Conclusion ProMuscle shows strong potential for scale up but requires a guided and coordinated approach. Successful scaling depends on collaboration between researchers, policymakers, and healthcare professionals, with clear responsibilities for sustainable funding and integration into routine care. Future efforts should focus on equity, long-term effectiveness, and adaptability across settings to ensure broad and lasting impact.