Abstract
ObjectiveTo assess the relationship between time-of-day of exercise training and changes in relevant cancer health outcomes among cancer survivors.MethodsRetrospective analysis of data collected from 2016–2019 from a hospital-based exercise oncology program. Descriptive statistics were calculated for demographic, clinical, and exercise timing characteristics (e.g. AM, PM, or mix) among survivors with available data for exercise training time (n = 233). For the total sample and a breast cancer sub-analysis, univariate analysis of covariance, adjusted for age, was carried out by exercise training time, for change in the following outcomes collected during the program’s assessment sessions: cardiorespiratory fitness and muscular endurance (human performance variables), physical function, anthropometrics, self-reported fatigue, and quality of life (QoL). Change in body mass index (BMI) and body weight was included in the breast cancer analysis.ResultsOverall, 37.3% of survivors habitually engaged in AM exercise (e.g. ≥ 75% AM training), 34.3% in PM exercise, and 28.3% in a mix of AM and PM exercise training throughout the program. Median time in the program was 17 weeks. Significant improvements in most human performance and physical function variables were observed in the total sample regardless of exercise training time-of-day. Among breast cancer survivors, PM but not AM or mixed was associated with improvements in fitness, and lower-body muscular endurance and function. Mixed exercise timing was linked with greater increase in waist circumference (total sample: 3.02cm, 95%CI 1.55, 4.49; breast cancer: 3.57cm 95%CI 0.96, 6.18), body weight (breast cancer: 1.6kg, 95%CI 0.3, 2.8) and BMI (breast cancer: 0.6kg/m2, 95%CI 0.1, 1.0). AM and PM exercise, but not mixed, was associated with improvements in fatigue and QoL.ConclusionTime-of-day of exercise training may differentially impact changes in human performance and physical function variables. Mixed exercise training time may result in less favorable outcomes related of weight management variables among cancer survivors.
Highlights
Substantial evidence supports the relationship between exercise engagement after a cancer diagnosis and attenuation of cancer treatment related side effects, improvements in quality of life, and reduction in risk of cancer-specific and all-cause mortality [1,2,3]
Exercise timing and cancer outcomes in cancer survivors human performance and physical function variables were observed in the total sample regardless of exercise training time-of-day
PM but not AM or mixed was associated with improvements in fitness, and lower-body muscular endurance and function
Summary
Substantial evidence supports the relationship between exercise engagement after a cancer diagnosis and attenuation of cancer treatment related side effects, improvements in quality of life, and reduction in risk of cancer-specific and all-cause mortality [1,2,3]. Evidence suggests that highintensity interval training may be superior compared with moderate-intensity continuous aerobic exercise for improving cardiorespiratory fitness in colorectal cancer survivors [7] This growing body of evidence supports the utility of exercise prescription and programming to promote favorable changes in relevant cancer health outcomes among cancer survivors. In other clinical populations, such as individuals with metabolic disease (e.g. obesity, type 2 diabetes), in addition to manipulation of exercise prescription, there is evidence to suggest time-of-day of exercise engagement may affect disease related health outcomes, such as weight status and body composition, glycemic control, and physical function. Afternoon and evening exercise is associated with greater exercise capacity, which may contribute to observations related to optimal
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