Abstract
PurposeTo investigate the effect of early evening exercise training at different intensities on nocturnal sleep and cardiac autonomic activity in endurance-trained runners.MethodsEight runners completed three experimental trials in a randomised, counterbalanced order. In the early evening (end of exercise 3.5 h before bedtime), participants performed either: (i) a 1 h high-intensity interval running session (HIGH, 6 × 5 min at 90% VO2peak interspersed with 5 min recovery); (ii) a 1 h low-intensity running session (LOW, 60 min at 45% VO2peak) or (iii) no exercise (CON). Subsequent nocturnal sleep was assessed using polysomnography, wristwatch actigraphy, and subjective sleep quality. A two-lead electrocardiogram recorded nocturnal cardiac autonomic activity.ResultsTotal sleep time increased after HIGH (477.4 ± 17.7 min, p = 0.022) and LOW (479.6 ± 15.6 min, p = 0.006) compared with CON (462.9 ± 19.0 min). Time awake was lower after HIGH (31.8 ± 18.5 min, p = 0.047) and LOW (30.4 ± 15.7 min, p = 0.008) compared with CON (46.6 ± 20.0 min). There were no differences between conditions for actigraphy and subjective sleep quality (p > 0.05). Nocturnal heart rate variability was not different between conditions, but average nocturnal heart rate increased after HIGH (50 ± 5 beats min−1) compared with LOW (47 ± 5 beats min−1, p = 0.02) and CON (47 ± 5 beats min−1, p = 0.028).ConclusionWhen performed in the early evening, high-intensity exercise does not disrupt and may even improve subsequent nocturnal sleep in endurance-trained runners, despite increased cardiac autonomic activity. Additionally, low-intensity exercise induced positive changes in sleep behaviour that are comparable to those obtained following high-intensity exercise.
Highlights
Elite athletes identify sleep as essential for recovery (Fallon 2007; Venter 2014)
heart rate (HR) incrementally increased with moderate- and high-intensity running
Maximum HR was 149 ± 14 beats min−1 during moderate-intensity stages and 176 ± 12 beats min−1 during high-intensity stages
Summary
Elite athletes identify sleep as essential for recovery (Fallon 2007; Venter 2014). during sleep many bodily processes occur, which are thought to be important for both physical and psychological restoration (Venter 2012). Teng et al (2011) measured sleep of elite road cyclists via wristwatch actigraphy during a “baseline phase”, “high-intensity phase”, and a “taper phase” They showed that sleep duration (7.0 vs 7.3 h) and sleep efficiency (84.27 vs 86.25%) were lower during the high-intensity phase compared to baseline. In overreached triathletes, Hausswirth et al (2014) reported a reduction in sleep duration (6:36 vs 7:09 h), sleep efficiency (88.4 vs 90.0%), and immobile time (387 vs 417 min) compared to baseline, before returning to baseline during the taper phase These findings may suggest high-intensity training or a high volume of training leads to sub-optimal sleep and recovery in endurance athletes
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