The effect of sleep quantity and quality on exercise and academic performance, autonomic function, wellness and cognition in youth athletes

The aim was to examine the effect of sleep restriction, fragmentation, and extension on athletic and academic performance, cognition, autonomic function, and mood of youth athletes. Sixteen pre-elite youth athletes completed four sleep experimental trials in a randomised-control design. Each trial included sleep restriction to 4 h (RES), sleep fragmentation by periodic waking throughout the night (FRAG), sleep extension to 10 h (EXT), or control/normal night sleep (CONT). The following day, testing included resting heart rate variability (HRV); exercise tests, Stroop task, and mood and wellness questionnaires. Time domain HRV data indicate no differences between conditions (P = 0.126 – 0.945, d = 0.11 – 0.67), while frequency domain indices indicate resting very low frequency (VLF) % contribution higher in RES compared to CONT and RES (P = 0.05, d = 0.86 – 0.96). Stroop reaction times were slower and accuracy lower in FRAG (P = 0.001–0.009; d = 1.90 – 2.55), while maths results were not different between conditions (P = 0.91; d = 0.13 – 0.58). There were no differences between conditions for sprint times, agility times, and vertical jump height (P = 0.38–0.98; d = 0.02 – 0.35). Throwing reaction task accuracy was lower in FRAG compared to CONT and RES (P = 0.006–0.05; d = 0.8) with moderate to large effects noted for throwing duration ( d = 0.43 – 1.21). Scores for ‘positive’ feelings were lower (P = 0.02 - 0.001; d = 0.51 – 0.99) and ‘negative’ feelings were increased for RES and FRAG compared to CONT (P = 0.003–0.08; d = 1.01 – 1.84). Perceived wellness was lower for RES compared to CONT (P = 0.016 – 0.0001; d = 0.9 – 2.34). Sleep fragmentation and restriction had no significant effects on anaerobic exercise performance or academic tests, but significant decrements were evident in mood states, autonomic regulation, and accuracy during complex cognition tasks.