Abstract
This study aimed to assess how female breast cancer survivors (BCS) respond physiologically, hematologically, and perceptually to exercise under heat stress compared to females with no history of breast cancer (CON). Twenty‐one females (9 BCS and 12 CON [age; 54 ± 7 years, stature; 167 ± 6 cm, body mass; 68.1 ± 7.62 kg, and body fat; 30.9 ± 3.8%]) completed a warm (25℃, 50% relative humidity, RH) and hot (35℃, 50%RH) trial in a repeated‐measures crossover design. Trials consisted of 30 min of rest, 30 min of walking at 4 metabolic equivalents, and a 6‐minute walk test (6MWT). Physiological measurements (core temperature (T re), skin temperature (T skin), heart rate (HR), and sweat analysis) and perceptual rating scales (ratings of perceived exertion, thermal sensation [whole body and localized], and thermal comfort) were taken at 5‐ and 10‐min intervals throughout, respectively. Venous blood samples were taken before and after to assess; IL‐6, IL‐10, CRP, IFN‐γ, and TGF‐β1. All physiological markers were higher during the 35 versus 25℃ trial; T re (~0.25℃, p = 0.002), T skin (~3.8℃, p < 0.001), HR (~12 beats·min−1, p = 0.023), and whole‐body sweat rate (~0.4 L·hr−1, p < 0.001), with no difference observed between groups in either condition (p > 0.05). Both groups covered a greater 6MWT distance in 25 versus 35℃ (by ~200 m; p = 0.003). Nevertheless, the control group covered more distance than BCS, regardless of environmental temperature (by ~400 m, p = 0.03). Thermoregulation was not disadvantaged in BCS compared to controls during moderate‐intensity exercise under heat stress. However, self‐paced exercise performance was reduced for BCS regardless of environmental temperature.
Highlights
Breast cancer accounts for 30% of all new cancer diagnoses, equating to one in seven women predicted to develop BC in their lifetime (Bray et al, 2018)
All were physically active to the extent that they self-reported they were able to complete the recommended World Health Organization (WHO) guidelines of physical activity (Bull et al, 2020), this was not assessed via activity monitors
The principal findings of this study are: (1) when exercising according to the current WHO-p rescribed guidelines (30 min of moderate exercise; ~4 METS) (Bull et al, 2020), thermoregulatory function, perceptions of effort, thermal comfort, and thermal sensation were similar between age-m atched controls and breast cancer survivors (BCS) in both warm and hot conditions; (2) functional exercise performance assessed, using a validated 6-minute walk test, was impaired in BCS regardless of the temperature the test was completed in; (3) of the markers of systemic inflammation measured, only C-reactive protein (CRP) was shown to be different between experimental groups and was ~0.33 mg·L−1 higher after exercise in BCS versus controls, regardless of environmental temperature, which is not enough to alter risk category for cardiovascular
Summary
Breast cancer accounts for 30% of all new cancer diagnoses, equating to one in seven women predicted to develop BC in their lifetime (Bray et al, 2018). Increasing physical activity is essential for BCS to begin to offset the reduced peak oxygen consumption (~20%) (Burnett et al, 2013; Jones et al, 2012), increased intermuscular fat (Reding et al, 2019), and prevalence of cardiovascular and/or myocardial injury post- cancer treatment (Beaudry et al, 2019; Jones et al, 2007), all prognostic of increased risk of cardiovascular disease-related all- cause mortality and reduced exercise tolerance. Survey and epidemiological data estimate that BCS reduce participation in physical activity by ~50% within a year post-treatment (Littman et al, 2010). Reductions in physical activity are not recovered long term, and post-treatment side effects are commonly reported as a barrier to exercise in this population, hindering patient's return to normal life (Fong et al, 2012)
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