Exercise therapy is an essential part of cancer rehabilitation. Home-based, unsupervised exercise programs supported by digital tools offer a promising way to reduce access barriers. However, guiding and monitoring exercise intensity without supervision remains difficult. Rating of perceived exertion (RPE) is often used for this purpose, but its validity in unsupervised, home-based settings has not been systematically examined. In this analysis, we evaluated whether RPE can guide and reflect objective exercise intensity, and explored factors influencing their alignment.

We conducted a secondary analysis using data from the intervention group of a multicenter randomized controlled trial. Seventy-six cancer survivors (breast, colorectal, or prostate cancer) followed a six-month, unsupervised, home-based, video-guided exercise program (2 × 30 min/week of individually tailored strength-endurance with different body-weight exercises). Heart rate (HR) during training sessions was recorded via chest strap. After each session, participants reported RPE for overall intensity using the Borg category-ratio 10 scale. We used mixed-effects models to examine the relationship between RPE and session-mean relative exercise intensity (%HRmax), and to identify factors including age, sex, beta-blocker use, and training week (the sequential week of the intervention), influencing discrepancies between perceived and HR-based intensity. Cross-tabulations assessed how accurately RPE identified sessions within guideline-recommended intensity ranges.

In total, 3533 exercise sessions were analyzed. RPE was positively associated with %HRmax (B = 1.64, p < 0.001, marginal R² = 0.066, intraclass correlation coefficient = 0.60). RPE identified sessions within guideline recommendations with a sensitivity of 87.4% and a specificity of 22.3%. Discrepancies between perceived and HR-based intensity were systematically associated with age (B = 0.037, p < 0.001), sex (B = 0.64, p < 0.001), beta-blocker use (B = − 0.39, p < 0.001), and training week (B = 0.032, p < 0.001).

RPE may help guide exercise intensity in unsupervised, home-based training for cancer survivors, but its limited alignment with physiological load may make it insufficient for precise monitoring. Objective feedback, such as HR monitoring, is needed to ensure adequate intensity in unsupervised settings. Future studies should explore factors influencing perceived exertion and test RPE across different exercise modalities.

DRKS-ID: DRKS00020499; Registered 17 March 2020; https://drks.de/search/en/trial/DRKS00020499.