Everyone always says, “Timing is everything,” and that definitely counts when it comes to fitness. If you’ve ever felt sluggish during an early-morning sweat or unmotivated and tired during a post-work gym session, you know just how true this can be.
Busy schedules tend to dictate when you have time to work out, but your personal sweet spot may vary depending on your fitness goals and internal body clock.
Consider An AM Sweat Session If…
You’ve probably heard quite a bit of back-and-forth about fasted cardio—a.k.a. cardio you do on an empty stomach, typically first thing in the morning. “While studies don’t definitively show any timing benefits for losing weight, the exercise window can be manipulated for training adaptation and performance purposes,” says Tasuku Terada, Ph.D., researcher at the University of Alberta in Canada.
So hitting the cardio bright and early may not be necessary if you’re trying to shed pounds, but sweating on an empty stomach may promote greater muscular aerobic adaptations—like your muscles’ ability to store glycogen (and prevent energy depletion) and their number of mitochondria, which help your cells produce more energy, says Terada. Both of these adaptations ladder up to how efficiently your muscles use oxygen—though more research to support these benefits is needed, Terada says.
To reap these muscular benefits, you’d need time to fast prior to hitting the gym, which is often easiest to do overnight, while you’re sleeping.
You may also want to consider morning workouts if you’re often plagued by sleepytime struggles. “For some individuals, rigorous exercise close to bedtime can stimulate the body and brain in a way that makes it difficult to fall asleep,” says Sina Gharib, M.D., sleep researcher and associate professor of medicine at the University of Washington.
The hormones released during and after exercise—like adrenaline, cortisol, and epinephrine—can have energizing effects for some folks. So if you have trouble falling asleep after a gym sesh and don’t have the luxury of sleeping in the next morning, it’s better to find time to work out earlier in the day. Ample sleep is crucial for benefiting from your workouts, after all, since your body uses that time to recover and grow stronger.
Consider A PM Sweat Session If…
Waking up at the crack-of-dawn to work out seems like the move (Did you crush leg day before work? Impressive.), unless, of course, it means you’re missing out on a full night’s sleep.
“The average person needs close to eight hours of sleep per every 24 hours,” says Gharib. If you fall short on that downtime, your body gets stuck in a state of constant breakdown, sabotaging your performance and progress. Waking up at five o’clock in the morning is even tougher when your progress stalls and motivation tanks.
If a morning workout cuts into your sleepy time, consider pushing your workout to later in the day, suggests Gharib.
Another reason to exercise later in the day: performance. Chowing down on carbs before endurance events—like a long run or race—helps improve your performance during the event, according to Terada. If you’re training for a distance running event or long obstacle race, fuel is crucial to your ability to kick butt. Since your body needs time to digest and process the carbs so they can be used as fuel, you’re best off hitting these workouts a couple of hours after a meal instead of first thing in the A.M.
Having proper fuel before a workout is also key if you’re trying to build muscle, so scheduling heavy lifts for lunchtime or after work may support your gains. “If your goal is muscle growth, protein supplementation becomes more important,” says Terada. Just like you want to get those carbs in before endurance training, you want to consume muscle-repairing protein before training for muscle growth—and afterward, too.
Related: How Much Protein Do You Really Need?
The Bottom Line
With all these different variables, penciling in the perfect time to work out probably feels a little daunting—especially if you choose to challenge your body differently and do different workouts from day to day. But here’s the good news: The best workout time for you ultimately boils down to your preference.
“The bottom line is, performing exercise at any time of day is better than no exercise,” says Terada. If you find a time that fits your daily life, you’ll be more likely to make it a routine and reap the benefits of a consistent healthy lifestyle.