| Summary: | It is accepted that exercise plays a significant role in breast cancer rehabilitation, but there has been limited emphasis on control and measurement of the intensity of exercise in cancer research. It is unknown how intensities achieved by different methods of intensity prescription compare, which complicates the interpretation and comparison of studies. The accuracy of these methods in achieving the prescribed intensity is also unknown; and methods that are inaccurate could be unsafe or ineffective in this population. Therefore, a cross-sectional study was performed to compare the achieved intensity and accuracy of four common methods of intensity prescription within and between three post-menopausal groups: breast cancer patients recently finished chemotherapy, survivors finished treatment and healthy controls (N=30). In randomized order, the metabolic equation for walking (MET equation), heart rate reserve (HRR), direct heart rate (direct HR) and rating of perceived exertion (RPE) methods were used to prescribe an intensity of 60% of oxygen consumption reserve (VO₂R) in separate 10-minute bouts, with recovery between bouts. Expired gas analysis was used to measure the intensity achieved during each bout. Accuracy was defined as: [60%VO₂R-achieved intensity]. In ranked order, the average achieved intensity (%VO₂R) and accuracy (percentage points (+/-ppts)) of the methods in the patient group were: HRR: 61%, 3 ppts; MET equation: 56%, 4 ppts; direct HR: 60%, 8 ppts; RPE: 53%, 9 ppts. The HRR method is recommended in this population based on accuracy and feasibility (no expired gas analysis or re-testing required). The MET equation method is also recommended, with re-testing to account for changes in peak oxygen consumption. The direct HR method could be unsafe, as it achieved intensities much higher than intended (77%), and would be ineffective in research where the effect of exercise is measured, as there was a large range of achieved intensities (42%). In the survivor group results were: MET equation: 59%, 3 ppts; HRR: 63%, 5 ppts; direct HR: 64%, 5 ppts; RPE: 47%, 13 ppts. The top three methods were comparable in accuracy in this group, and appear to be safe and effective, while the RPE method was inaccurate and is not recommended.
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