For endurance athletes of all levels, sleep is a key to recovery and performance. But how do you know when enough is enough? And what can you do to get more?

Catching enough Zs is so important to triathlete Nathanael Horne that he sometimes tells his fiancée to sleep on the couch if she comes home late the night before a major race.

“I try to get eight hours if I’m coming up to a big event,” says the 35-year-old. “Everyone has different sleep requirements; I seem to require more.”

The grind of construction outside and long hours as an allergy and immunology doctor sometimes prevent Horne from drifting into dreamland. “In New York it’s incredibly difficult to get an adequate amount of sleep,” he says. “New Yorkers professionally work harder than anyone else in the world. If you are an athlete as well, you have even less time. One of the first things to fall by the wayside is sleep.”

While a busy life creates a barrier between Horne and his bed, slipping into the sheets is no problem for Ironman triathlete Iwan Axt. His troubles begin when it’s time to doze off. “After a hard swim, I have difficulty sleeping,“ he says. “It’s been bad enough that I’m thinking of getting a new bed.”

The connection between endurance athletes and sleep is still not fully understood, sleep experts say. Robert Basner, director of the Cardiopulmonary Sleep and Ventilatory Disorders Center at Columbia University, says few studies have produced conclusive results about the relationship between endurance training and sleep. He explains that while it’s clear that exercise causes fluctuations in people’s metabolic and cardiac systems that can positively or negatively impact their rest, it is hard to point to one cause for good or bad sleep.

“People have looked at sleep deprivation and injury and in terms of performance training and injuries there are some studies that show no effect and some that show effect,” he says. “Because there aren’t definite studies we can’t say we know it’s bad for you.” He adds that it is also unclear if too much training hinders an athlete’s ability to get shut eye, explaining that, “if you are exhausted you tend to sleep better, but it’s not clear you’ll maintain sleep. You can exhaust yourself to the point that you can’t sleep.”

While Axt believes his late-night swim the night before a morning bike ride is probably contributing to his sleep difficulty, new runner Lori-Ann Wynter is encountering the opposite.“Before a deep sleep was 20 minutes. Now a deep sleep is midnight to 6 a.m.,” says Wynter, who joined The Running Center six months ago. “That’s a big step. Sleeping the way I do now is really new to me.”

Wynter also says that a combination of changing her diet from lots of carbohydrates at night to a lighter snack has also helped her fall asleep faster and sleep for longer stretches.

David Schulman, director of the sleep disorders laboratory at Emory University in Atlanta, says there are multiple reasons sleep can be disrupted, including alcohol and caffeine consumption and eating and working out too close to bedtime.

He advises athletes not to drink caffeine within 10 or 12 hours of their bedtimes and not to eat within 2 hours of their scheduled sleep start. He also suggests leaving at least 5 hours to unwind after a workout before hitting the hay.

If athletes are still having difficulty, he recommends evaluating environmental obstacles that are preventing them from mentally relaxing.“You have to make sure the bedroom is dark and quiet,” he says. “Make sure you don’t have a TV or music on. There are only two things you should do in bed: sleep and sex. You should not be reading in bed. The bedroom needs to be sanctuary for sleeping.”

Sometimes barriers to sleep are within an athlete’s own mind. “One problem could be a psycho-somatic stress related to an upcoming event,” he says. “ If you’ve got something important in athletic life, you will have insomnia related to it.”