Objective:

To investigate the effects of endurance training on skeletal muscle and hepatic metabolic health under chronic circadian rhythm disruption, focusing on training status and exercise duration.

Approach:

• Study Design: Twenty-four male Sprague–Dawley rats were assigned to four groups: regular sleep cycle sedentary (RSC), irregular sleep cycle sedentary (ISC), irregular sleep cycle with late-stage endurance training (ISE), and irregular sleep cycle with prolonged endurance tr…
• Circadian Disruption Induction: Circadian rhythm disruption was induced by alternating light–dark cycles every three days for 20 weeks.
• Endurance Training: Endurance training was performed at moderate intensity, with varying durations between groups.
• Analysis: Skeletal muscle and liver samples were analyzed for circadian clock proteins, mitochondrial biogenesis, glucose and lipid metabolism, oxidative stress, and fibrosis-related markers.

Key Findings:

• Circadian rhythm disruption impaired circadian clock regulation, mitochondrial biogenesis, and metabolic function in skeletal muscle and liver.
• Reductions in BMAL-1 expression, AMPK activation, PGC-1α signaling, and oxidative phosphorylation were observed.
• Endurance training mitigated changes induced by circadian disruption, with prolonged training showing greater improvements in mitochondrial and metabolic adaptations.

Interpretation:

Limitations:

• The study was conducted on a specific rat model, which may limit generalizability to other species.
• Only male rats were used, which may not represent female metabolic responses.

Conclusion: