Ask the Expert: What Is the Best Time of Day to Exercise?

Ask the Expert: What Is the Best Time of Day to Exercise?

You’ve likely heard this advice countless times in one form or another, but that doesn’t make it any less true: The best time of day to exercise is when you have the most energy and motivation—in short, when you’re most likely to do it.

Sure, there are studies that extol the benefits of exercising at specific times (more on that in a bit), but as long as you’re smart about how you exercise, any kind of workout (cardio, HIIT, weightlifting, etc.) can be performed at any time of day and produce results.

In fact, scheduling your workout for the time of day that works best for you will almost always produce the most dramatic ones, because it increases your odds of maximizing the most important workout variable of all: Exercise adherence. Simply put, the more consistently you work out, the more likely you are to see results.

That said, if you’re flexible and don’t have a preferred workout time, you can potentially achieve your goals faster by scheduling your workouts strategically.

Potential benefits of morning workouts: Greater weight loss through improved fat burning.
Potential benefits of afternoon/evening workouts: Improved aerobic performance and faster strength gains.

When Is the Best Time of Day to Exercise?

The best time to work out is when you WILL work out. That might seem obvious, but the significance of that advice can’t be overstated. Why? Because workout consistency is the most important variable of all when it comes to achieving any fitness goal.

That means that if you’re a night owl, work out at night. Morning person? Work out first thing in the morning… you get my drift. Any time you’re in the mood to really “bring it” will work because, by far, the biggest physiological changes happen to your body when you push yourself further than you’ve pushed yourself before. There’s a reason why the P90X mantra is “Bring It”: The closer you get to putting in 100 percent effort, the more you force your body into an adaptive state, which is exactly where it needs to be in order to change.

While temporal “nit-picking” can help make your fitness journey easier—lifting weights in the evening might be slightly more beneficial for building strength than doing so in the morning, for example—it can also work against you if you get too wrapped up in it. Exercise and healthy eating will always trump all other advice. I’ve seen every excuse in the book, including “I missed my optimal window for training so I skipped today’s workout.” Don’t let this happen. Unless you’re injured, sick, or overtrained, exercising is better than not exercising, so always schedule your workout when you have the best chance of getting it done.

But if you enjoy nit-picking, and have a flexible schedule and no preference for AM or PM workouts, read on for the three best times to work out, depending on your goal.

1. When your glycogen stores are full

Best for: Boosting aerobic performance, especially endurance
Best time: Late morning, afternoon, and early evening

Your body can push itself longer and harder aerobically if you begin your workout with a full tank of muscle and liver glycogen, which is the stored form of your body’s primary fuel, glucose.

Glycogen is replenished by carbohydrates, and is extinguished very quickly through exercise, brain activity, and most other tasks. This means it fluctuates throughout the day and is always highest in the hours after you digest a meal containing carbohydrates. As a result—and depending on your eating schedule—your body is probably primed for peak exercise in the late morning, afternoon, or early evening.

At night, your body can store glycogen, meaning that it’s possible to wake up and train in the morning before you’ve eaten and still have enough energy to get through a workout, but that is a theoretical scenario. Most of us, especially when we’re training hard and not eating a ton, will burn through glycogen recovering from the prior day’s activities.

The result is that those early morning workouts can lead to something called “the bonk,” which is what happens when your body runs out of glycogen. Essentially you lose the ability to push your aerobic envelope, and you feel like you’ve hit a wall.

Bonking is not one of those “good pain” times, but it’s inevitable that it will happen to you at some point. When it does, don’t try and push though. Instead cut your losses and get on the recovery program by eating, resting, and then reevaluating your eating schedule and/or choice of workout times.

If exercising when your glycogen stores are low (e.g., in the morning) is the only time of day available, you can fix the situation nutritionally. Eat a half (or even a whole) banana, or have a cup of watered down juice before you work out. That will boost the levels of glucose in your blood, so you won’t have to tap into your glycogen stores as much. Alternatively, you can try to top off those stores by adding an extra serving of complex carbohydrates to your evening meal. If neither strategy works (you’ll know if it doesn’t—bonking isn’t subtle), it means you’re on a nutritional edge and aren’t eating enough total daily calories to recover from your workouts. It’s time to reevaluate your daily caloric intake.

2. When your stomach is empty

Best for: Burning fat and losing weight
Best time: Morning

In the morning, before you’ve eaten, your body is more likely to tap fat stores for energy during aerobic workouts, and you can train your body to become more efficient at doing so, which is cool. You’re also “burning fat,” which sounds even cooler. While fantastic in theory, it’s not so fun in practice if you force your body into a situation where you bonk.

You won’t bonk, however, unless you’re training at a very high intensity or running or cycling for a very great distance. This means low intensity workouts can have added benefits if done in the morning on an empty stomach. This is why in programs like P90X Doubles, we scheduled the lowest intensity workout of the day for the morning.

In the case of P90X Doubles, however, that lower intensity morning workout is a strength session, and thus requires additional nutritional steps to optimize recovery. The reason is that your body doesn’t store protein, so if you strength train before you “break fast,” you’ll put your body into a catabolic (breakdown) state, which, as you might imagine, is less than optimal for building muscle. Fortunately, it’s easy to reverse the situation: Have a protein shake, like Beachbody Performance Recover, or a protein-rich meal within a half hour of completing your workout.

Here are two more weight-loss advantages of an AM workout: It can decrease your appetite and inspire you to be more physically active throughout the day, according to a study at Brigham Young University, in Utah. What’s more, sweating early in the day can improve the duration and quality of your sleep later on, according researchers at Appalachian State University. That’s important because adequate sleep (more than eight hours a night) is associated with greater fat loss if you’re trying to slim down.

3. When your body temperature peaks

Best for: Building strength
Best time: Late afternoon/evening

Your body temperature drops while you sleep, which is one reason you might wake up stiff and lacking flexibility. The discs between your vertebrae also fill with fluid as you slumber, making them more susceptible to injury first thing in the morning. Either way, it’s best to wait at least an hour after waking before you start pumping iron or doing exercises that require you to flex your spine (e.g., crunches), especially if you suffer from back pain. And if you can wait to work out until later in the day, all the better.

Here’s why: Your body temperature climbs throughout the day, peaking between 4:00 and 6:00 PM. As it rises, so too does muscle strength and power, according to a study in the Scandinavian Journal of Medicine & Science in Sports. What’s more, Scottish researchers report that exercise-induced increases in testosterone production are greatest in the late afternoon and early evening.

In sum, if you’re looking to maximize strength gains, it’s best to schedule your workout for after work, or even during your lunch hour, rather than try to cram it in before you leave for the office. But there’s always a “but,” and in this case it has to do with a principle known as “temporal specificity,” which states that your body will adapt to be strongest at the time of day during which you normally train. So while you might initially benefit from late afternoon strength workouts, you’re better off scheduling those workouts for (you guessed it) whenever they’re most convenient for you.

Is It OK to Exercise Before Bed?

Unless it is really the only time you will work out or the only time you feel the best, you should probably avoid it. The reason is that working out directly before bed can affect your sleep.

Most people have a hard time getting to sleep after a workout because exercise can throw off your melatonin, the hormone that regulates sleep, among other things. This isn’t ideal because sleep is very important for recovery. It’s when your body naturally produces most of its own performance-enhancing drugs in the form of hormones. If possible, eliminate anything that hurts your ability to sleep.

Exercise also utilizes a lot of nutrients, which are further depleted at night. If you’re on a strict diet, perhaps trying to lose weight, you run further risk by training and then not eating to recover from the workout prior to bed. If you’re on a low-calorie diet and plan to train hard at night, you should follow your workout with a nutritional recovery strategy, such as Beachbody Performance Recharge or a small meal before going to sleep.

I’m not the norm, so I’ll play the counterpoint to my point as I can fall asleep (and often sleep much better) immediately after a very hard workout. If you’re like me, there’s nothing wrong with training at night. Just follow nutritional protocols that don’t leave you depleted and starving when you wake up. I’ve done this and it can be so severe that you wake up in the middle of the night, a common issue with bodybuilders and fitness trainers getting ready for competition. This is not ideal as it means your body is essentially bonking during sleep. And while that’s okay if your goal is to pose in front of a crowd with absurdly low body fat, like a bodybuilder, it’s also a sign of starvation and, if done too long, will cause your body to begin to shut down its metabolic processes.

The bottom line is that everyone’s body responds differently. We all need to exercise and most of us can eat better. In between are a lot of individual variables. When it comes to getting your best possible workout, psychology often trumps physiology. Exercise when you can and pay close attention to your performance. Then choose your preferred workout time based on your results. It’s really that simple.

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