What time you exercise doesn’t affect muscle force or reduce blood sugar, study shows

The ability of skeletal muscle to produce force (contractile function) and contraction-stimulated glucose uptake (increase in clearing sugar from bloodstream) do not differ by time of day, regardless of sex or muscle type.

The first-of-its-kind study directly investigated intrinsic contractile function or glucose metabolism in skeletal muscle over a 24-hour circadian cycle. The findings are published in the journal Function.

A growing body of research suggests that these two factors vary by time of day, while chronobiological effects on intrinsic skeletal muscle properties are thought to be the underlying mediator.

To test their theory, researchers measured intrinsic contractile function and endurance, as well as contraction-stimulated glucose uptake in mice four times per day.

“Overall, these results suggest that time-of-day variation in exercise performance and the glycemia-reducing benefits of exercise are not due to chronobiological effects on intrinsic muscle function or contraction-stimulated glucose uptake,” the research team wrote.

More information:
Liam S Fitzgerald et al, Intrinsic Skeletal Muscle Function and Contraction-stimulated Glucose Uptake Do Not Vary by Time-of-day in Mice, Function (2024). DOI: 10.1093/function/zqae035