Lower rate-pressure product during submaximal walking: a link to fatigue improvement following a physical activity intervention among breast cancer survivors

Research showing a link between exercise-induced changes in aerobic fitness and reduced fatigue after a cancer diagnosis has been inconsistent. we evaluated associations of fatigue and rate-pressure product (rpp), a reliable index of myocardial oxygen demand, at rest and during submaximal walking following a physical activity intervention among post-primary treatment breast cancer survivors (bcs). secondary analyses of 152 bcs in a randomized controlled trial testing a physical activity intervention (int) versus usual care (uc) were performed. the int group completed counseling/group discussions along with supervised exercise sessions tapered to unsupervised exercise. evaluations were made at baseline and immediately post-intervention (m3) on measures of physical activity (accelerometry), graded walk test, and average fatigue over the previous 7 days. rpp was calculated by dividing the product of heart rate and systolic blood pressure by 100. resting and submaximal rpps were significantly improved in both groups at m3; however, the magnitude of change (∆) was greater in the int group from stage 1 (∆rpp1; int −13 ± 17 vs. uc −7 ± 18; p = 0.03) through stage 4 (∆rpp4; int −21 ± 26 vs. uc −9 ± 24; p < 0.01) of the walk test. the int group reported significantly reduced fatigue (int −0.7 ± 2.0 vs. uc +0.1 ± 2.0; p = 0.02) which was positively associated with ∆rpp during stages 2–4 of the walk test but not ∆aerobic fitness. lower rpp during submaximal walking was significantly associated with reduced fatigue in bcs. exercise/physical activity training programs that lower the physiological strain during submaximal walking produce the largest improvements in reported fatigue.