Safety and Feasibility of Long‐Term High‐Intensity Interval Training With and Without Peer Support in Cancer Survivors

Despite the benefits of physical activity and exercise, including high-intensity interval training (HIIT), few cancer survivors meet the exercise oncology guidelines. Emerging evidence suggests peer support (i.e., assistance from individuals with lived experiences trained in behavior change techniques) may improve exercise adherence, yet its long-term safety and feasibility remain unclear. This study evaluates the safety and feasibility of 12 months of HIIT, with and without peer support, in cancer survivors. Breast, prostate, and colorectal cancer survivors completed 4 weeks (12 sessions) of supervised HIIT before being randomized to receive weekly peer support from people with lived experience of a cancer diagnosis (HIIT+PS) or no peer support (HIIT-Only) for 12 months. Both groups were provided 12 months of free access to local gymnasiums. Safety (adverse and severe adverse events) and feasibility (recruitment, attrition, attendance, adherence to intensity, duration, mode, peer supporter contact) were compared to a priori criteria. The a priori criterion was met for recruitment rate (38%) of study participants (n = 137). Peer supporters (n = 32) contacted participants 0.8 ± 0.5 times/week (n = 40 contacts/participant), preferring text messaging (50%) or face-to-face (41%) contacts, meeting the a priori criterion (0.77 contacts/week). Both groups met the a priori criteria for safety (n = 0 severe and n = 7 (0.5%) Grade 1/2 adverse events), duration, and mode, but not attendance or intensity across the full 12 months. A priori criterion for study attrition was met in the intervention group (23.7%) but not the HIIT-Only group (30.8%). Twelve months of HIIT with and without peer support was safe with participants meeting the prescribed duration, and mode, but not attendance or intensity. Peer support provided weekly for four of every 5 weeks appears insufficient to improve HIIT feasibility. Peer supporters preferred to provide contact via text messaging or face-to-face interactions. Future studies should explore strategies to improve long-term HIIT frequency and intensity adherence. Trial Registration: Australian New Zealand Clinical Trial Registry 12 618 001 855 213. Registered 14 November 2018. Trial registration includes all components of the WHO Trial Registration Data Set, as recommended by the ICMJE.