Research on exercise and time of day is growing, but still limited and and not without controversy. In general, if you can find a time for exercise that you can stick with consistently, you will be much more likely to train regularly and get better results.
Circadian Rhythms and ExerciseHuman sleep and wake cycles follow a daily cycle called circadian rhythms. It's this cycle that regulates our body temperature, blood pressure, alertness and metabolism, among other physiological functions. In general, these rhythms conform to our 24-hour day and may be reset based upon environmental cues. The time of day that we typically exercise is one of these cues. Research by the University of North Texas, in Denton found that although circadian rhythms are inborn we can reset them based upon our behaviors. For example, using an alarm clock, establishing meal times and even when we workout are all cues to help rest our rhythms. They found that people who consistently exercise in the morning "teach" their body to be most ready for exercise at that time of day. When they switched to evening exercise, they didn't feel as strong.
The ability to adjust your rhythms is important for athletes training for a specific event. The message is to train at the same time of day that the event will occur. Research supports this advice. Studies show that your ability to maintain exercise intensity will adapt to your training time. Therefore, if you do your marathon training in the morning, you may perform better on race day (marathons typically start in the morning). But if you train in the evening, a morning race day may leave you feeling weaker and slower.
Individual Differences and Exercise TimingSome people are just naturally morning people. They have no trouble exercising first thing in the morning. Others don't get moving so quickly and are more likely to feel like exercising later in the day. If you have such an obvious preference it's pretty easy to decide what sort of exercise schedule you might stick with. The interesting thing is that research shows that no matter when you think you are better able to exercise, almost all of us are, in fact, physically stronger and have more endurance in the late afternoon.
Scheduling ExerciseNot everyone can choose to exercise when they feel like it. Work and family commitments often take priority and we end up squeezing in some exercise. If you find that the only time you have to exercise is when you least feel like it, don't despair. As we learned earlier, you can change your rhythms and your body can adapt to a new exercise time. However, it may take about a month to reset your internal exercise clock. (get tips on adjusting your circadian rhythms during air travel).
Research and the Best Time to ExerciseWhile there is specific research being conducted on this topic, unfortunately the answer to the question, "What is the best time for exercise?" varies based upon the specific question you ask, your training goals, and your exercise adherence. Here are some of the latest specific research findings:
- Late Afternoon is Best for Exercise
Research shows that the optimal time to exercise is when our body temperature is at its highest, which, for most people is 4 p.m. to 5 p.m. (body temperature is at its lowest just before waking).
- Strength is Greater in the Afternoon
Dr. Hill reported that strength output is 5% higher at around mid-day; anaerobic performance, such as sprinting, improves by 5% in the late afternoon.
- Endurance is Greater in the Afternoon
Aerobic capacity (endurance) is approximately 4percent higher in the afternoon.
- Injuries Are Less Likely in the Afternoon
Afternoon exercise is the best if you want to avoid injuries for many reasons. We are most alert; our body temperature is the highest so our muscles are warm and flexible; and our muscle strength is at its greatest. These three factors make it less likely that we will get injured.
- Morning Exercisers Are More Consistent
Even though afternoon exercise might be optimal from a physiological standpoint, research also shows that morning exercisers are more likely to stick to it that late-day athletes.
- Evening Exercise and Sleep
Most research supports the idea that exercise can improve sleep quality. But does exercising too late in the evening keep you up? Studies have shown improvements in sleep from both morning and afternoon exercise, so it's not yet clear if evening exercise keeps you up. One study even showed that vigorous exercise half an hour before bedtime did not affect sleep.
One thing that is agreed upon is that sleep deprivation can hinder sports performance.
The Bottom Line
The good news is that you get to decide the best time for you to exercise based upon your personal goals, schedule and lifestyle. Ideally, you will pick a time that you are able to stick with consistently and make part of your daily or weekly schedule. If you are training for competition, it's wise to modify your training to accommodate the event start time, and it's always wise to warm up before any workout. Also See: Why Your Workouts Don't Work.
David W. Hill; Kirk J. Cureton; Mitchell A. Collins, Circadian specificity in exercise training, Ergonomics, Volume 32, Issue 1 January 1989, pages 79 - 92.
Youngstedt, S. t al. Is sleep disturbed by vigorous late-night exercise?[, Medicine & Science in Sports & Exercise. 31(6):864-869, June 1999.
Medarov, B.I. "Hour-to-hour variation of FEV1/FVC" Chest Medarov 126 (4): 744S.