The Perfect Day: Tapping Into The Circadian Rhythm

When To Exercise
Some people—whether by choice or by necessity—are morning exercisers. Others are afternoon or evening exercisers. Of course, many triathletes are both. When is the best time to exercise?

Studies have shown that most people perform better and also feel more comfortable when they exercise in the afternoon. For example, in a 2009 study, French researchers recruited 16 competitive cyclists and had them perform a high-intensity exercise test at both 6 a.m. and 6 p.m. The test consisted of a maximal one-minute effort on a stationary bike against resistance. Researchers measured the cyclists’ peak power output, their mean power output for the first 30 seconds of the test, and their mean power output for the full minute. On average, the subjects performed roughly 8 per cent better in each of these metrics in the afternoon than in the morning. But why?

“Our body temperature is lowest when we wake up in the morning,” says Portman. “Then it increases until about 2 or 3 in the afternoon. That’s the high point of the day. There’s been a fair amount of research done with endurance athletes and resistance athletes which shows that performance does improve when you exercise when your body temperature is peaking.”

That settles it. If you work out once a day, you should do it in the afternoon, when you can perform better and, by performing better, get a bigger fitness-boosting stimulus from the work. Right? Not so fast. Other research has shown that exercise performance improves most at the specific time of day when workouts are habitually performed. So, if you always work out in the afternoon, your afternoon exercise performance will increase more than your morning workout performance. And if you always work out in the morning, your morning workout performance will improve more than your afternoon workout performance. For example, in a 1998 study, researchers at the University of North Texas put a group of college-age female non-athletes through a five- week high-intensity cycling interval training night. Half of the women did all of their workouts in the morning. The rest did theirs in the afternoon. At the end of five weeks, all of the subjects performed two separate high-intensity rides to exhaustion, one in the morning and one in the afternoon. The morning exercisers performed significantly better in the morning test, while the afternoon exercisers put up much better numbers in the afternoon test. When do most triathlons take place?

Early in the morning. Therefore, even if you are an afternoon exerciser by habit, you’ll want to consistently do some workouts in the early morning so that your race performances aren’t compromised by a lack of specific physiological adaptation to exercising at that time of day.

So, where does this leave us? If triathlon is one of the most important things in your life and you have the time, habitually exercising twice a day most days is your best bet. Not only will you become fitter than you would on a once-a-day training regimen by virtue of greater training volume, but you will enjoy the benefits of being able to work harder in your afternoon workouts and the specific improvements in morning exercise performance that come with training in the morning.

If you cannot or prefer not to exercise twice a day most days, then you’ll want to be sure to routinely do some of your workouts in the morning. If you’re normally a morning exerciser, go ahead and do all of them in the morning. If you’re normally an afternoon exerciser, breaking from that habit once or twice a week should be enough to avoid putting yourself at a disadvantage in morning races.

FILED UNDER: Training TAGS: About / advice / Circadian / day / eat / exercise / how-to / Information / perfect / rhythm / sleep / Tips