Effects Of Exercise Timing On Sleep Quality And Functional Capacity In Cancer Patients Undergoing Treatment

PURPOSE: It is well established that chronic exercise can provide significant health benefits in the cancer population, and recent studies have suggested that the benefits of chronic exercise may be influenced by the timing of exercise within a 24-hour day. The purpose of this study was to investigate the effects of exercise timing on measures of sleep quality and functional capacity in cancer survivors. METHODS: Cancer survivors currently receiving chemotherapy and/or radiation were recruited for this study. Exercise sessions occurred 1 hour/day, 3 days/week for 12 weeks. Participants were separated into an AM group (exercise conducted at 6 AM, 7 AM, or 8 AM) (n = 6) or PM group (exercise conducted at 4 PM, 5 PM, or 6 PM) (n = 4). Each participant wore a commercially available sleep tracking device throughout the entirety of the 12-week intervention. RESULTS: Exercise training resulted in significant increases in total sleep time (hours) for the AM (0.39 ± 1.63 hours, p < 0.007) and PM (0.47 ± 1.27 hours, p < 0.001) exercise groups. The AM group had a significant increase in light sleep (0.65 ± 1.27 hours, p < 0.001) and the PM group had a significant increase in deep sleep (0.15 ± 0.6 hours, p = 0.02) and REM sleep (0.2 ± 0.97 hours, p = 0.05). The AM group had a significant decrease in REM sleep (-0.24 ± 0.86 hours, p = 0.002). Heart rate variability significantly increased in the AM group (7.42 ± 13.7 ms, p < 0.001) and significantly decreased in the PM group (-8.83 ± 22 ms, p < 0.001). The AM group had a significant increase in chair test repetitions (3.6 ± 1.81, p = 0.01), and the PM group had a significant increase in VO2 peak (4.3 ± 2.07 mL·kg−1·min−1), p = 0.02) and lower body strength-to weight ratio (0.4 ± 0.04, p < 0.001). DISCUSSION: Timing of exercise had a significant impact on several outcomes. The AM group saw increases in total sleep time, light sleep, HRV, and chair test reps, but the PM group showed no significance in these parameters except for a decrease in HRV. These data suggest that exercise timing may influence outcomes related to sleep quality and functional capacity in cancer survivors.