This One Workout Timing Change May Benefit Your Nervous System
You know those mornings when you manage to squeeze in a workout before your inbox starts filling up, only to wonder whether it actually makes a difference when you exercise?
The answer may be a little more nuanced than "a workout is a workout." In new exercise timing research, scientists compared morning workouts with afternoon and evening sessions to see whether the clock could influence how people felt and recovered.
The results suggest that when you move may matter for more than your fitness.
About the study
Researchers at the University of Northern Colorado Cancer Rehabilitation Institute followed 44 people with cancer who were undergoing treatment through a 12-week supervised exercise program.
Participants chose one of two workout windows, either 7 to 9 a.m. or 4 to 6 p.m. Everyone completed physical and psychological assessments before and after the program.
A smaller group of 24 participants also wore trackers overnight to monitor their sleep and recovery.
The researchers were particularly interested in whether workout timing affected not just physical fitness, but also mood, sleep, and the autonomic nervous system. This system helps regulate automatic processes such as heart rate and the body's response to stress.
Morning workouts had an edge beyond fitness
Both groups became stronger and more physically capable after 12 weeks, so the basic fitness benefits of exercise didn't appear to depend on the time of day.
The differences showed up in some of the other measures.
People who exercised in the morning had greater improvements in depressive symptoms and sleep quality than those who exercised later in the day. They also experienced an increase in heart rate variability (HRV), a measure that can provide insight into how the nervous system responds to stress and shifts back toward recovery.
The afternoon and evening group, meanwhile, saw their HRV decrease. The researchers considered the differences large enough to be clinically meaningful, rather than simply statistically significant.
Your body clock may be part of the equation
One possible explanation is your circadian rhythm, the internal clock that helps coordinate sleep, wakefulness, hormones, and other daily processes.
Morning activity can reinforce signals that tell your body it's time to be awake and active.
Exercise later in the day isn't inherently harmful, but it happens closer to the period when your body is preparing to wind down.
That could help explain why the morning group saw greater changes in sleep, mood, and stress regulation, even though both groups improved their physical fitness.
It's important not to stretch these findings too far. This was a relatively small study involving people undergoing cancer treatment, so we can't assume the same effects would occur in every population.
If mornings work for you, there's a reason to try them
If you're already a morning exerciser, these findings offer another potential reason to keep the habit. If you're not, you don't necessarily need to become one.
Try moving a workout earlier in the day when it's practical, even if that means shifting your wake-up time by 20 minutes at first, and pay attention to how you sleep, feel, and recover.
If your schedule or energy levels make evening exercise a better fit, that's still a valuable time to move.
The participants who exercised later improved their fitness, too, and training consistently is what protects your muscle over the long run.
The takeaway
Workout timing may influence more than how fit you become.
For some people, exercising earlier could also support sleep, mood, and the body's ability to handle stress.