If you work out after work, you might be disrupting your sleep, especially if your workouts are intense.

A new Australian study has found a clear link between late-night exercise and poor sleep. We spoke to Dr Josh Leota from Monash University’s School of Psychological Sciences to break down the findings.

Why Study Evening Workouts?

Dr Leota said the idea came from years of working with elite athletes. “The number one complaint has always been having difficulty sleeping after matches,” he explained.

While previous studies had mixed results, this research looked at a much larger sample, nearly 15,000 people over a year. The data showed strong patterns that hadn’t been clear before.

What Did the Study Find?

The study used data from wearable fitness trackers, collecting about 4 million lines of information. It looked at how people exercised, when they exercised, and how they slept.

The key takeaway? “When people were going all out within four hours of their usual bedtime, we saw sleep disruptions,” said Dr Leota.

These disruptions included:

  • Later bedtimes
  • Shorter sleep
  • Poorer sleep quality
  • Higher resting heart rate during sleep

Timing Matters, But So Does Intensity

Dr Leota stressed that intensity is crucial. “We found a dose-response relationship,” he said. “The more intense the exercise, the more recovery time you need before sleep.”

For example:

  • Very intense exercise (like a 15km run or a competitive sports match): Allow at least four hours before bed.
  • Light activity (like walking your dog or gentle cycling): Can be done as close as one hour before bedtime without affecting sleep.

What’s Happening in Your Body?

After intense workouts, your body stays in a state of high alert.

“You activate the sympathetic nervous system, your ‘fight or flight’ mode,” Dr Leota explained.
“Your heart rate stays high, your body temperature is up, and it’s hard to wind down.”

But for sleep, your body needs to switch into “rest and digest” mode, which takes time.

What About Eating Late?

Exercising late often means eating late too, and that can also affect sleep.

“Delaying your meal can delay sleep onset,” Dr Leota said. “And your body will focus on digestion instead of preparing for sleep.”

So try to eat as soon as you can after your workout.

Caffeine and Alcohol Can Make It Worse

Many gym-goers take pre-workout supplements that are loaded with caffeine. “Avoid caffeine in the afternoon if you want quality sleep,” Dr Leota advised.

He also mentioned that alcohol, often consumed after social games, can disrupt sleep. “Limiting alcohol helps support better sleep,” he said.

Morning Workouts Are a Better Option

If possible, shift your high-intensity exercise to earlier in the day.

“Morning workouts help reset your circadian rhythm,” said Dr Leota. “You’re more alert during the day and sleepier at night, which is what you want.”

Plus, there are mental health benefits. Morning exercisers report feeling more focused and positive throughout the day.

Final Thoughts

Dr Leota is clear, exercise is good, even at night. “We’re not discouraging exercise. Any exercise is better than none,” he said. But if your goal is to sleep well, try to:

  • Do intense workouts earlier in the day
  • Stick to lighter activity if you’re exercising within four hours of bedtime
  • Avoid late caffeine and alcohol
  • Eat promptly after exercising

Bottom line? Exercise smart. Give your body time to unwind, and your sleep will thank you.

Listen to the full conversation below.