Some people leap out of bed ready to tackle the day, while others take their time easing into the morning.
Whether you’re cheerful at sunrise or slow to get moving, your natural rhythm — known as the circadian rhythm — may be influencing your habits more than you realize.
Scientists have long known that this internal timing system governs when we sleep and wake, but its reach extends well beyond that.
It also influences key processes in the body, including metabolism, body temperature and hormone release.
Now, a study from University of Florida Health, with funding from the National Institute on Aging, suggests that not just how active you are, but when you’re active during the day, may relate to better health outcomes — especially as you grow older.
The study looked at older adults and found that those who were active earlier in the day and maintained a steady daily routine had better cardiorespiratory health and were more efficient walkers than those who were active later or had more irregular patterns.
Dr. Karyn Esser, senior author of the study, explains in the paper that while exercise has long been associated with healthy aging, this research hints that timing might be just as important as the activity itself.
The research, published in Medicine & Science in Sports and Exercise (April 2025), doesn’t claim that changing your routine will automatically boost fitness.
Rather, it shows a connection that warrants further study.
Dr. Esser notes the need for more investigation to determine whether adjusting the timing of exercise or physical activity could directly lead to better health, and whether these findings apply to younger people as well.
In short, a causal relationship has not been established.
For all we know, the reason for these findings could be that those who start their exercise early in the day may also be more inclined to, for example, eat more fresh vegetables – and perhaps it’s the vegetable intake that leads to better outcomes in older age.
How the Study Was Done
Roughly 800 older adults, averaging 76 years of age, participated in the study.
For one week, they wore wrist devices that tracked their movement around the clock.
Later, they completed fitness tests that measured how well their heart and lungs worked during exercise.
Study Findings
Participants who had a stronger difference between their active and restful periods tended to perform better on fitness tests.
Those who were most active earlier in the day showed better heart and lung function, as well as more efficient walking.
People whose daily activity patterns were more predictable — happening around the same time each day — also experienced better results.
Importantly, the study considered all types of movement, not just structured workouts.
This included daily tasks like walking, household chores, gardening and shopping.
The body’s internal timing system helps sync many bodily functions with the day-night cycle.
Disruptions, such as those caused by travel or working overnight shifts, can negatively affect sleep, mood and physical abilities.
While this study doesn’t offer a guaranteed formula for improving health, it does suggest that aligning your daily routine with your body’s internal signals might be beneficial.
Another important point is that this study in no way suggests that exercise routines that take place later in the day or in the evening aren’t significantly beneficial to one’s health.
Most fitness enthusiasts probably work out after business hours simply because this is the only chance they get to hit the gym or conduct their home workouts.
- So if you can’t switch your exercise regimen to early morning, don’t fret.
- Keep doing what you’re doing!
Lorra Garrick is a former personal trainer certified by the American Council on Exercise. At Bally Total Fitness, where she was also a group fitness instructor, she trained clients of all ages and abilities for fat loss and maintaining it, muscle and strength building, fitness, and improved cardiovascular and overall health.
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