The extensive survey of 1,000 U.S. adults by the National Sleep Foundation found that while exercisers and non-exercisers slept roughly the same amount of time each night, the more physically active people reported significantly better sleep quality, fewer sleep problems, and more daytime energy than those who got little activity.

And while many people think that exercising too close to bed is a surefire sleep stealer, the survey actually found that when people worked out had no effect on their sleep quality, concluding that “exercise, or physical activity in general, is generally good for sleep, regardless of the time of day the activity is performed.”

For the survey, vigorous exercise included running, swimming, cycling and team sports; moderate exercise included yoga, tai chi and weightlifting; light exercise included walking. Here, a peek inside some of the more fascinating findings:

* Exercisers sleep better: 83 percent of vigorous exercisers report fairly to very good sleep quality, compared to 77 percent of moderate exercisers, 76 percent of light exercisers, and 56 percent of non-exercisers.

* Exercisers fall asleep more easily: A full 69 percent of vigorous exercisers, who take 16.6 minutes to fall asleep on average, say they rarely or never have trouble nodding off, compared to half of non-exercisers, who take 26.3 minutes.

* Exercisers wake up happy: 46 percent of vigorous exercisers say they rarely or never wake up feeling unrefreshed, compared to 27 percent of non-exercisers.

* Exercisers have more get-up-and-go: Half of vigorous exercisers report that they have had no problem “maintaining enthusiasm to get things done” over the past two weeks, which is significantly higher than respondents who categorized themselves as moderate exercisers, light exercisers and non-exercisers.

* Non-exercisers are more likely to drive drowsy: Compared to those who exercise, non-exercisers report the highest proportion of having trouble staying awake while driving, eating, or engaging in social activities (14 percent vs. 4 to 6 percent).

* Non-exercisers are java junkies: Those who don’t exercise say they drink an average of five caffeinated beverages on workdays, which is significantly more than their exercising counterparts (vigorous: 3.1 beverages, moderate: 3.3 beverages, light: 3.6 beverages).

* Non-exercisers are more prone to sleep apnea: More than four in ten (44 percent) non-exercisers are at a moderate risk for sleep apnea, significantly higher than all segments of exercisers. In fact,  6 percent of non-exercisers are at a high risk for sleep apnea compared to 0 percent to 1 percent of exercisers.

One note: the survey results can’t prove cause and effect. While exercise may very well lead to better sleep, it may also be the case that people who are able to exercise also have fewer health problems and therefore are more prone to sleep well than people who don’t exercise.

However, there are many biologically plausible explanations for how exercise improves sleep and fights daytime fatigue, according to the National Sleep Foundation. For one, many conditions linked with sleepiness, including obesity, diabetes, and sleep apnea, are also associated with higher levels of inflammatory chemicals—and exercise reduces levels of these substances. Exercise may also promote sleep by causing changes in body temperature that signal the brain it’s time to feel tired. And exercise may  relieve feelings of depression and anxiety, which are linked to insomnia.

More tips for snagging good sleep:

Tricks for the Perfect Nap

Snooze-Happy Secrets from Unusual Experts

Easy Food Fixes for Insomnia

What Does Your Sleep Position Say About Your Personality?

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