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Background: Supramaximal high-intensity interval training (HIT) programmes can be challenging to replicate outside research settings. This study aimed to explore its feasibility for older adults in a community setting, incorporating perspectives from exercise participants and instructors.

Methods: A pragmatic feasibility study using a convergent mixed- methods design involving four exercise instructors from one training facility and 21 older adult exercise participants (14 women, age-range 65–78). The previously used HIT programme consisted of 20-minute sessions that included a warm-up, ten 6-second intervals, and cool-down. Instructors first adapted the programme around these core components to their setting and then conducted 25 sessions. Both qualitative (individual interviews) and quantitative (estimated maximal oxygen consumption, estimated 6-second power, exercise- related motivation, and self-efficacy) data were collected and analysed (content analysis and descriptive statistics) in parallel. A taxonomy for implementation outcomes was used as an analytical matrix.

Results: Experiences of both participants and instructors revealed that the structure of the training was regarded as engaging, enjoyable, and supportive for establishing routines and promoting ownership of training progression. Participants found personalised and motivating approaches to engage with the programme and confidence in their abilities grew. Changes in exercise-related motivation and self-efficacy showed individual variation without a group trend. Participants who completed the intervention showed a positive median change in estimated 6-second power and maximal oxygen consumption, although individual responses varied. Experienced challenges included coordinating tasks during intervals and confidence in managing the programme. Barriers to fidelity and to scale-up were related to the practical complexity and fixed structure.

Conclusions: Supramaximal HIT can be implemented for older adults in a community setting with appropriate support, including individualised watt-based intensity and structured progression. The findings highlight how participants took ownership of their intensity progression, enabling them to challenge their limits. However, the fixed structure and complexity in managing short intervals may pose barriers to broader adoption. To enhance feasibility and scalability, simplifying interval management and providing clear, structured guidance are recommended. These insights help refine and optimize supramaximal HIT implementation for older adults in community settings.

Trial registration: Open Science Framework 31 January 2023 (https://doi.org/10.17605/OSF.IO/B7T2G).