Differential benefits of 12-week morning vs. evening aerobic exercise on sleep and cardiometabolic health: a randomized controlled trial.

None

Consistent, regular moderate-intensity aerobic exercise causes significant changes in body composition, lipid profile, sleep latency, and artery function, and benefits may vary according to exercise timing.

Introduction

This study aimed to determine whether morning or evening aerobic exercise affects sleep and cardiometabolic health in sedentary men.

Methods

This 12-week randomised controlled trial recruited sixty-five sedentary men aged between 18 - 28 years. Participants were randomly assigned to the morning exercise (ME: 6 – 8 a.m.), the evening exercise (EE: 6 – 8 p.m.) or the control (CON) groups. The intervention programme involved at least three sessions of moderate-intensity aerobic exercise with a total of ≥150 minutes every week. Assessments of body composition, sleep, blood metabolic markers, and carotid arterial ultrasound were conducted before and after the intervention.

Results 

After the 12-week intervention:

Sleep patterns

• The ME group exhibited advanced sleep onset, mid-sleep and sleep end times compared to pre-exercise. Notably, sleep schedules in the ME group were significantly earlier than the EE group (e.g. workday sleep onset ME: 23:36 vs EE: 00:05).

• Both ME and EE groups showed reduced sleep latency on workdays and work-free days (ME: ~ 6.70 minutes; EE: ~4.57 minutes) without any significant changes in sleep duration, which aligned with an advanced dim light melatonin onset (DLMO) in the ME group.

• Cardiometabolic health

  • Both ME and EE groups showed significant reductions in body fat mass, visceral fat, subcutaneous fat, and waist-hip ratio, without any significant changes in weight.

  • ME showed significant reductions in total cholesterol and triglycerides compared to the CON group.

  Hemodynamics

  • Both ME (63.34 ± 1.35 vs. 70.85 ± 1.89) and EE (64.85 ± 2.32 vs. 73.37 ± 2.85) groups showed reductions in resting heart rate (HR), stiffness index and pressure-strain elastic modulus. The ME group showed a lower HR than the CON group (63.34 ± 1.35 vs. 71.53 ± 1.56).

  • EE group showed increases in maximum and mean arterial diameters, maximum flow velocity, flow rate and pulsatility index. Whereas dynamic resistance and peripheral resistance decreased.

Conclusion

• Exercise timing is an important factor when tailoring interventions for sleep and cardiometabolic health.

• Healthcare practitioners should discuss exercise timing, type and intensity when tailoring health interventions especially with clients who have both sleep and cardiometabolic disorders.

• When supporting sedentary male clients presenting with elevated levels of triglycerides or total cholesterol, scheduling morning aerobic exercise sessions may help decrease subcutaneous and visceral body fat content faster, as well as reducing triglyceride and total cholesterol levels.

• For clients with high blood pressure or vascular dysfunction, evening exercising may be better given that the EE cohort showed improvements in systolic blood pressure, carotid blood flow velocity, and arterial dilation.

• Individuals struggling with delayed sleep phase or having difficulty falling asleep may benefit from a morning exercise plan as only the ME cohort was able to show earlier DLMO in addition to shorter sleep-onset latency.

• The study involved only sedentary adult males thus future studies should aim to also include female and older participants to determine whether there are any differential timing effects of exercise.

• Future research should expand the study range to cover subjects with cardiovascular disease and/or metabolic diseases to better understand the effectiveness of interventions that could benefit people with preexisting illnesses.

• Research could include subjects with disrupted circadian rhythms, such as shift workers and individuals with insomnia, to gain insight into how timed exercise affects sleep disorders.