Abstract
STUDY OBJECTIVES: Using the necessary replicate-crossover design, we investigated whether there is interindividual variability in home-assessed sleep in response to acute exercise. METHODS: Eighteen healthy men (mean [SD]: 26[6] years) completed two identical control (8 hour laboratory rest, 08:45-16:45) and two identical exercise (7 hour laboratory rest; 1 hour laboratory treadmill run [62(7)% peak oxygen uptake], 15:15-16:15) trials in randomized sequences. Wrist-worn actigraphy (MotionWatch 8) measured home-based sleep (total sleep time, actual wake time, sleep latency, and sleep efficiency) two nights before (nights 1 and 2) and three nights after (nights 3-5) the exercise/control day. Pearson's correlation coefficients quantified the consistency of individual differences between the replicates of control-adjusted exercise responses to explore: (1) immediate (night 3 minus night 2); (2) delayed (night 5 minus night 2); and (3) overall (average post-intervention minus average pre-intervention) exercise-related effects. Within-participant linear mixed models and a random-effects between-participant meta-analysis estimated participant-by-trial response heterogeneity. RESULTS: For all comparisons and sleep outcomes, the between-replicate correlations were nonsignificant, ranging from trivial to moderate (r range = -0.44 to 0.41, p ≥ .065). Participant-by-trial interactions were trivial. Individual differences SDs were small, prone to uncertainty around the estimates indicated by wide 95% confidence intervals, and did not provide support for true individual response heterogeneity. Meta-analyses of the between-participant, replicate-averaged condition effect revealed that, again, heterogeneity (τ) was negligible for most sleep outcomes. CONCLUSIONS: Control-adjusted sleep in response to acute exercise was inconsistent when measured on repeated occasions. Interindividual differences in sleep in response to exercise were small compared with the natural (trial-to-trial) within-subject variability in sleep outcomes. CLINICAL TRIALS INFORMATION: https://clinicaltrials.gov/study/NCT05022498. Registration number: NCT05022498.