Effects of sleep extension combined with HIIT exercise on cortisol, IGF-1, and lactate levels in adolescents with sleep disorders: A randomized controlled trial

Background and aims: Sleep disorders are associated with hormonal and metabolic disturbances in children and adults. This study aimed to investigate the effect of high-intensity interval training (HIIT), a sleep extension program, and the combination of both on blood cortisol (C), insulin-like growth hormone (IGF-1), IGF-1/C ratio, lactate concentration, and aerobic capacity (AC) in adolescent girls with disorders. Methods: This randomized controlled trial involved 80 girls with sleep disorders (aged 14.81±1.46 years) recruited from the Child and Adolescent Psychology Clinic of Langerod in 2022. They were randomly divided into four groups using Random Allocation Software: HIIT, a sleep extension program, a combination of HIIT+sleep extension, and a control group (n=20 per group). They participated in pre-test and post-test sessions for laboratory measurements and AC tests. The HIIT and combined groups followed the RAST protocol for four weeks, with three sessions per week. In addition, each participant in sleep extension and combined groups adhered to the sleep schedule for four weeks. Results: A paired t test revealed significant reductions in cortisol levels for the sleep extension and combined groups (P=0.006). Moreover, IGF-1, IGF-1/C ratio, lactate, and AC significantly improved in all three intervention groups (P<0.001). The analysis of covariance (ANCOVA) test showed significant differences between groups for cortisol (F=64.361, P=0.001), IGF-1 (F=21.706, P=0.0001), IGF-1/C (F=33.76, P=0.001), lactate (F=34.845, P=0.001), and AC (F=26.106, P=0.001). Conclusion: The findings provide evidence that combining HIIT with sleep extension can be an effective and safe intervention for improving the outcomes of sleep disorders in adolescent girls.