by Hunter Bennett,The Conversation

Credit: Matt Garrow/The Conversation.Adapted from Delos,CC BY

Your alarm goes off. Somehow you manage to get dressed, drag yourself to the gym, and start squatting.

But why does it feel so hard? Your legs are heavy and the weight you lifted only a couple of days ago—in the afternoon—feels almost impossible.

No, you're not imagining it. There'sa large body of evidenceto suggest most of us are stronger, more powerful, and have better endurance later in the day.

There are several reasons exercising can feel much harder first thing in the morning. Here's why, and how you can adjust to morning exercise if you need to.

Your body has a natural 24-hour clock that regulates hormones, body temperature and when you feel most awake or ready for sleep.

This clock is called your circadian rhythm. It iscontrolled by the brainbut can also be influenced by external factors such as sunlight. This might explain why exercising in the morning in winter can be especially hard for some of us.

Research showsyour circadian rhythm is clearly linked to exercise performance, which tends to follow a daily pattern.

Most people reach their peak between 4 and 7pm. This means we tend to be stronger, faster and more powerful in the afternoon and early evening.

We don't know exactly why. But there are a few potential explanations.

Yourcore body temperatureis at its lowest around 5am, and steadily increasesacross the day. When your body temperature rises, yourmuscles contractmore efficiently. We think this is part of the reason people aretypically stronger and more powerfullater in the day.

Insulin—the hormone that regulates blood sugar (glucose) levels—tends to behighestin the morning. This leads to a decrease inblood sugar, meaning less glucose your body can use as fuel, likely affecting how hard you can push.

While we don't know exactly why, there is some evidence to suggest yournervous systemis better atsending signals to your musclesthroughout the day. This allows you touse more of your muscle fibersduring exercise, essentially making you stronger.

Your sleep chronotype can also affectexercise performance.

This describes your natural inclination for sleep and wakefulnessat certain parts of the day—basically whether you're a "morning person" (an "early bird"), or feel more productive and alert in the evening (a "night owl").

Research shows night owls with a late chronotypedo notably worsewhen exercising in the morning, compared to people with an early chronotype.

While we don't know why this is the case, it might be that night owls experience smaller fluctuations in hormones and temperature throughout the day—although this is just speculation.

Interestingly, being sleep deprived seemsto affect physical performancein the afternoon more than in the morning. So if you're staying up late and not getting much sleep, you may actually find it easier to exercise the next morning than the next afternoon.

Whatever time of day, if you can feel yourself working, you will make progress—for example, increasingmuscle strengthand improvingaerobic fitness and heart health.

So if you're exercising to get bigger, stronger and fitter, the timing doesn't actually matter.

Besides, "when" we exercise often comes down to motivation and convenience. If you like to exercise earlier in the day and that suits you best, there's no reason to change.

If you have asporting eventcoming up in the morning—and you usually train in the afternoon—you might want to prepare by doing some early exercise so you're at your peak.

There is evidenceto suggestthat repeatedly training in the morning can close the gap between your afternoon and morning performance.

Basically, your body can get used to exercising at a particular time, although it will likely take a few weeks to adapt.

Finally, if you find exercising close to bedtime makes you feel too alert and isdisrupting your sleep, you may want to try doing something more gentle at night and/or exercising earlier in the day.

This article is republished fromThe Conversationunder a Creative Commons license. Read theoriginal article.

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