07/17/2008 05:12 am ET Updated Nov 17, 2011

Can't Get to Sleep? Try Exercise in the Late Afternoon

I'm not the first person to tell you that exercise is good for you. But if there's one magic bullet for enhancing the quality of your sleep, it's exercise. Because sleep and exercise are both vital signs of good health, if you can accomplish both well, you're way ahead of the game. But now there's more to this bit of advice if you're a victim of insomnia: scheduling an exercise session in the late afternoon might be your magic bullet to end the sleeplessness.

A new study just came out pointing the benefits of late-day exercise on people who have trouble falling asleep.

Specifically, people who engaged in moderate aerobic exercise in the evenings, such as 50 minutes on the treadmill, fell asleep more quickly, woke less often, and increased their total sleep time. Sorry, but no sleep-promoting benefits were reported for strength training or a heavy workout.

This is not news to me and I hope this study, which confirms earlier findings, further encourages natural ways to support healthy sleep rather than resorting to drugs or exercise-avoidance (people with insomnia are not usually advised to work out in the evenings because of the potential rousing effect of exercise).

Why Aerobic Exercise Promotes Sleep

Not everyone experiences the same sleep benefits from exercise, but when you think about it, people who suffer from insomnia aren't usually the athletes and active individuals. (The only instance I've seen is where athletes over-train and for some reason have a hard time turning
their mind off at night, or they are so used to exercising that on their "off days" their body craves that exercise to help with sleep.)

To the contrary, most people who complain of sleep problems lead sedentary lives and don't practice a regular exercise routine. Aerobic exercise has shown to aid in sleep primarily by doing two things:

-- helping you fall asleep quicker

-- plunging you into deep (or delta) sleep for a longer period of time, which is where you need to be
to feel refreshed and restored the next day.

Studies on people who participate in aerobic activities show that they have a tendency to
secrete more growth hormone at night, which aids in repairing and
rejuvenating the body.

How exactly does this happen?

One current reasoning behind exercise's effects on sleep centers of the brain is the thermogenic hypothesis, which states that exercise promotes sleep by heating the body or brain.

When you work out (again, it has to be an aerobic workout for at least 20 to 30 minutes), your
body's core temperature rises a couple of degrees and stays that way for about 4 to 5 hours. When it cools back down, your core temperature will decrease to a point lower than had you not worked out at all.

It's this drop in body temperature that is theorized to promote going to sleep more quickly as well as deep, sound sleep. Hence, the late-afternoon, early-evening workout could be the ideal time. Those with insomnia who don't exercise would do well to experiment with late-day workouts and see if they do the trick.

How an Insomniac Can Get the Most Out of Exercise's Sleep Benefits

-- Get a physical and rule out any medical issues that may be causing your insomnia, or that you need to address before getting active if you haven't been so in a while.

-- Experiment with exercise at different times of the day, starting with late-day workouts about 5 to 6 hours before bedtime. Record the quality of your sleep in a sleep journal. Find out, for example, if you sleep better after morning, noon, or evening workouts. Exercise can be stimulating if you do it too close to bedtime.

-- Be sure to get your heart rate up for at least 20 to 30 minutes most days of the week. Even if they don't have immediate sleep benefits, strength training and stretching are a must for total body fitness.

-- Build your fitness level slowly; don't jump into a strenuous fitness routine too quickly.

-- Exercise in bright outdoor light if possible. This time of the year, it's pretty easy to have ample light in the evenings for a brisk stroll around the neighborhood.

-- Don't stress too much over finding the perfect time to exercise. That's unrealistic. It's hard enough to worry about fitting the time in to schedule a workout than it is to time it perfectly.

How much exercise will affect your sleep will be a factor of the level of intensity at which you work out, how long you work out, as well as how fit you are to begin with. Just go do it, though. Any exercise is good exercise... and your sleep will enjoy it.

This post is cross-posted at Dr. Breus's official blog, The Insomnia Blog.