Eric Martin, Claudio Battaglini, Beth Hands, Fiona L. Naumann

The aim of the present study was to determine if exercise intensity impacts upon the psychosocial responses of breast and prostate cancer survivors to a rehabilitation program. Eighty-seven prostate and 72 breast cancer survivors participated in an 8-week exercise and supportive group psychotherapy intervention (n = 84) or control (n = 75) group. Intervention participants were randomized to low-to-moderate intensity exercise (LIG; n = 44; 60-65 % VO2peak, 50-65 % one repetition maximum (1RM)) or moderate-to-high intensity exercise (HIG; n = 40; 75-80 % VO2peak, 65-80 % 1RM) while controls continued usual care. Before and after the 8 weeks, all participants completed the Functional Assessment of Cancer Therapy-Breast or -Prostate to assess quality of life (QOL) and Behavioural Regulations of Exercise Version 2 for exercise motivation. Intervention participants also completed a follow-up assessment 4 months post-intervention. All three groups improved in QOL from baseline to post-intervention, with no significant differences. From post-intervention to follow-up, the LIG and HIG similarly maintained QOL scores. Between baseline and post-intervention, both intervention arms improved their motivation to exercise compared to the controls (p = 0.004). At the 4-month follow-up, the HIG had maintained their overall exercise motivation (p < 0.001) and both domains of intrinsic motivation (identified regulation, p = 0.047; intrinsic regulation, p = 0.007); however, the LIG had regressed. The structured intervention was successful at improving autonomous exercise motivation, regardless of exercise intensity. However, only those participants who had exercised at a higher intensity sustained their improvement. Intervention participation did not improve QOL more than controls. Higher-intensity exercise is more likely to result in more sustainable increases in motivation to exercise among cancer survivors.