For me, the most challenging part of exercising is finding the time to do it. With my schedule, working out at night is often easiest—but should I believe the people TikTok telling me that an evening gym sesh won’t have the same payoff?

I’m not an early riser. I’m not even the type to get up as soon as the alarm clock goes off. If I have a choice, I prefer to start the day calmly, postponing the alarm, scrolling through the news and social media, and having a leisurely breakfast. My only option is to work out in the late afternoon, which is a controversial choice. Sure, it can be stressful to wait until the last possible second to finally cross exercise off the list, but for me it’s also a way to end the day on a good note.

Still, I envy those who can pull off a comprehensive morning workout. I also wonder if my evening endorphins will have a negative effect on my sleep, which is the most common gripe with evening workouts. The good news: Experts say that it’s not always that cut and dried.

“From a physiological standpoint, ‘late’ is not so much the time itself, but how close it is to bedtime,” professional trainer Juan Antonio Martín explains. “It’s considered nighttime training when you train within two hours of sleeping.” That means if you go to bed at 11 p.m., any time after 9 p.m. is too late to start exercising. “Ideally, there should be a minimum margin of 90 to 120 minutes between the end of training and bedtime,” Martín says.

How do evening workouts affect sleep?

There is validity to the claim that exercising at night can affect sleep. When you work out, you activate the sympathetic nervous system (also known as the fight or flight response) and increase core body temperature, which can have a negative effect on sleep, according to Martín. “Exercise, especially if it’s high intensity like strength or HIIT, also increases the release of catecholamines like adrenaline,” he says. “And that’s all great…except when you need to relax and sleep.”

Training too late can throw your circadian rhythm out of whack if you’re sensitive to this kind of stimulus, which can make it harder to reach a deep sleep, Martín says. Not everyone is affected in the same way, but if you notice that you find it hard to sleep after exercising, your body is already giving you a clue.

How to exercise at night without compromising your rest

In short: The more demanding the workout, the more time you’ll need before trying to sleep. The harder you train, the more your body is activated and your nervous system is kept alert. The time it takes for the body to return to normal is proportional to the intensity of the training.

While it may interrupt some people’s sleep routines, exercising at night is not categorically bad for you. “There are people whose peak energy and performance is not in the morning, but in the afternoon or evening,” Martín says. “In those cases, forcing workouts early in the morning can lead to worse results: more fatigue, less adherence, and even risk of injury.”

Essentially, it’s a matter of lifestyle. If hitting the gym right after you wake up seems unfathomable but training at night helps you shake off the day’s stress, Martín says to listen to your body. A late afternoon or evening workout can even help improve your mood and give you a sense of accomplishment before bedtime. “The important thing here is to be honest with yourself. If training at night makes you feel better and doesn’t affect your sleep, keep doing it,” the trainer says.

Is it more effective to work out in the morning than the evening?

Sleep concerns aside, lots of people also assume that morning exercisers see better results than those who work out before bed. But that’s another misconception, Martín says: No matter when you train, the benefits in terms of fat loss and muscle mass gain are the same.