Best time to work out: what the research actually says

The best time to work out is the time you'll actually keep, week after week. Studies comparing morning and evening training find similar long-term gains in strength, muscle and fitness; evenings have a small edge for peak performance, and your body partly adapts to whatever hour you train. The clock only really matters for sleep, competitions and the way your own day behaves.

So if you've been waiting to start until you find the optimal hour, that stopped being a training question a while ago. It's an excuse with a stopwatch. Here's what the research says, and when the details are worth caring about.

What the studies compared, and what they found

The most thorough summary so far is a 2023 review in Sports Medicine – Open by Fabienne Bruggisser, Frank Scheer and colleagues. They screened more than 14,000 papers and kept 26 articles (22 distinct studies, 713 participants) that compared training at different times of day. Their verdict: the evidence is neither for nor against any specific time being better for performance or health. They also rated the risk of bias in most of those studies as high, and the participants were mostly young men.

An earlier meta-analysis focused on lifting, by Grgic and colleagues in Chronobiology International (2019, 11 studies), landed in the same place: gains in strength and muscle size were similar whether people trained in the morning or in the evening.

The honest headline is boring. For the results most people care about over months, the hour barely moves the needle. Showing up moves it a lot.

Why 6 p.m. feels easier than 6 a.m.

That doesn't mean both hours feel the same. The 2023 review points out that performance measures like strength, power and jump height tend to peak in the late afternoon or evening. Body temperature, which climbs during the day, is one of the usual suspects.

What matters even more is your own clock. A 2015 University of Birmingham study of athletes, by Elise Facer-Childs and Roland Brandstaetter, found that an individual's performance varied by as much as 26% over the course of a day. The best predictor of when someone peaked wasn't the time on the wall: it was how long they'd been awake. Early birds and night owls peaked at different hours.

Two practical consequences:

• If you train fifteen minutes after your alarm, you're meeting yourself at a low point. Give morning sessions a longer warm-up and don't judge your strength by the first set.
• Mornings improve with practice. The Grgic meta-analysis found that training in the morning can bring morning strength up to roughly evening levels. Your body learns the appointment.

The case for mornings

Mornings have one unbeatable advantage: nothing has happened yet. No meeting ran late, no friend has suggested tacos, and the couch hasn't had eight hours to make its case. If your evenings are unpredictable, that alone can settle it.

There's also a hint that mornings help a routine stick. In a small 2017 study by French researchers (Fournier and colleagues, in Health Psychology), 48 students added a simple stretch to their day for 90 days, either right after waking or right before bed. By the researchers' estimate, the morning group reached the point where the stretch felt automatic sooner: around 106 days against 154. It was one stretch, not a workout, so treat it as a clue rather than a verdict.

The cost of mornings is sleep. If a 6 a.m. session means going to bed at the usual time, you're trading the thing that makes training work for the training itself. Adults need at least seven hours, so move bedtime first; there's a full guide on how to wake up early without wrecking yourself. And if the weak link is the alarm, Toxic Coach's alarm keeps going until you finish a wake-up mission, like solving math or scanning something in your bathroom.

The case for evenings, and the sleep question

Evenings give you a warmed-up body, a meal or two in the tank and, for many people, a better mood for a hard session. The usual worry is that exercising at night ruins sleep.

For most healthy people, it doesn't. A 2019 meta-analysis by Stutz and colleagues in Sports Medicine pooled 23 studies and concluded that evening exercise does not hurt sleep. The one caveat: vigorous exercise that ends an hour or less before bedtime might make it harder to fall asleep and trim your sleep a little.

So easy evening sessions can happen whenever. Hard intervals or a brutal leg day should finish at least an hour before bed.

The bigger risk with evenings is everything that happens before them. Every hour between waking up and training is another chance for something to cancel it. If you choose evenings, protect the slot like an appointment and leave home with your gym bag, so "I'll just stop by the house first" isn't part of the plan.

One kind note: if you lie awake most nights no matter when you train, that's not something a gym timetable will solve. Persistent trouble sleeping deserves a conversation with a doctor, because it's treatable. Our guide to fixing your sleep schedule is a good place to start too.

When the clock does matter

A few situations where timing is worth planning around:

• You compete at a set time. The 2023 review found some evidence that training and testing at the same time of day pays off, mostly for performance. If your race starts at 8 a.m., do some key sessions at 8 a.m.
• You work shifts. Since time awake predicts performance better than the clock, anchor sessions to when you wake up, not to "morning" or "evening."
• You sleep badly. Keep the hardest sessions away from bedtime and watch how you respond.
• You manage a health condition. If you have diabetes or a heart condition, or take medication that affects your energy or blood sugar, ask your doctor whether timing matters for you.

For everyone else, the right answer is boring on purpose.

Pick your slot in ten minutes

Do this once, then stop thinking about it:

1. Look at the last month. Which hour was free most often? Not the ideal hour, the real one.
2. Choose the slot the fewest people can cancel.
3. Do the sleep math. If the slot costs you sleep, move it.
4. If it's late, keep the hardest work at least an hour before bed.
5. Commit for four weeks before you judge it. Changing times every week is how "flexible" turns into "never."

Not a morning person? Fine. Nobody's asking you to become one. Train at 7 p.m. and stop using your body clock as a reason to skip both.

Your move this week

Put your slot in the calendar for the next two weeks, at the same time on every training day, and treat it like a meeting you can't move. Not sure how many of those slots you need? Read how many days a week to work out. If the real problem is showing up at all, start with how to go to the gym consistently.