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What is the best time to work out? What the science says

I wanted to start of this article by making it clear that if you are not working out regularly, this article probably is not for you. The first step for you would be to find the time during the day that is most suitable for you to build a habit of a regular exercise. On the other hand, if the only thing that can keep you away from the gym is an injury, then you might want to continue reading this article.

Work out timing is often overlooked by many, but it is possible to increase your performance and recovery time just by tweaking your workout schedule and the time of the day you go to gym. Studies have shown long term muscle size and strength gains in groups training at different times during the day.

Scientific studies

Several studies have been made comparing morning and evening workouts by Kuusma et al. 2016. One group was performing work outs in the morning between 6:00 - 10:00 h, and the other group between 16:30 - 20:00 h. Strength and endurance improved similarly, however, evening group had a higher muscle growth. This supports that muscle anabolic signaling is higher in the afternoon compared to the morning.

Laczo et al presented another data comparing morning and afternoon groups, with afternoon groups having on average 10% higher muscle growth.

Tim Sheett performed a study on bodybuilders to compare different work out times. One group trained before 10 in the morning, and the other group trained after 6 in the evening. Results: morning group had an increase of muscle size by +0.6% and an increase in fat mass by +5%, while the evening group had an increase in muscle size by +3.2% and a decrease in fat mass by -4% over a period of 10 weeks. Both groups trained 4 times a week.

What is really happening here? Why is one group doing better than the other one? Lets explore even further.

Circadian Rhythm

Circadian rhythm is a daily cycle of biological activity. Your body has an internal clock, by which it regulates your sleep, hunger, nervous system and hormones. To illustrate it have a look at the image below.

The ones that are most important for us, are the hormonal, body temperature and energy metabolism differences.

Hormonal differences

We primarily care about the two hormones, testosterone and cortisol. Testosterone is a good hormone that directly helps us build more muscle by affecting the number of satellite cells. Cortisol is a stress hormone and has catabolic effects on muscle tissue. What we want is the to find the time during the day where the difference between the two is highest. This is also called T/C ratio. Have a look at the graph below.

Testosterone production during the day

Cortisol production during the day

Based on the graphs above, the highest T/C ratio is in the afternoon and evening. What this means is that during this period, exercise causes the smallest increase in cortisol and the largest increase in testosterone. Based on this, the optimal time to train is late afternoon or early evening.

Body temperature

For strength training purposes, your body performs better during a higher body temperature. It improves nerve conduction velocity, joint mobility, glucose metabolism, and muscular blood flow. It also helps you achieve higher muscle activation levels. This means that your body temperature correlates with your performance.

So what is the circadian rhythm for your body temperature?

Body temperature is low at night, rises quickly upon awakening, and reaches a maximum in the evening. Your glucose uptake is also more efficient meaning your body can use energy more efficiently.

Your optimal time to train according to this is late afternoon and early evening.

Also if you look at athletes and their performance, most sports record are broken in the early evening.

Best time to work out

Best time to work out would be anywhere from 3 pm to 9 pm in the evening. Your hormonal and body temperature circadian rhythm is at the optimal level. This is of course if you have a normal sleep biorhythm 12:00 - 8:00. However if you are either working night shifts or staying up late and waking up later in the day, make sure to have at least 6 hours between waking up and working out.

When experimenting with at what time your performance is best, you can also use a heart rate as a guideline. Resting heart rate is correlated with your body temperature. This means that when your resting hart rate peaks, its the time to work out.

What if you can't work out in the afternoon or evening?

Sometimes it is a luxury to be able to plan your workouts at an optimal time during the day. Perhaps you work in the evening, or you have classes, dates, social gatherings etc. In this case, there are a couple of solutions to still save your workouts.


A dose of 250 mg of caffeine in the morning rises neuromuscular readiness close to the afternoon levels. It basically switches your body to daytime mode.

However, research shows that most of these effects are actually psychological. Tinsley et al. 2017 confirmed that 300 mg of caffeine did not have a greater effect on subjective energy levels compared to the placebo group! Basically telling people they just consumed 300 mg of caffeine is just as effecting as actually giving them the real caffeine.

Another problem with caffeine is that to effectively work for our purposes, which is strength training, you need to consume 3+ mg / kg of body weight. You start to develop tolerance to caffeine with anything above 1.5 mg / kg. The problem is obviously sustainability. Soon enough 3 mg / kg will not be enough and you will need to increase the dosage again.

The main issue that I have with caffeine is that it can disrupt sleep. Just a single espresso 16 hours before going to sleep can impair sleep quality by reducing the amount of time you spend in deep sleep.

Caffeine also decreases T/C ratio and does not elevate morning growth hormone levels to afternoon levels.

As such, I would not recommend this option if you can only work out early in the morning.


The best way to improve your performance during sub-optimal time is to always train at the same time. This way, your body will adapt to it, and change the circadian rhythm. Your nervous system can adapt quickly however your hormones will adapt less well. This is why research shows small differences in strength but bigger differences in muscle growth.

If you are working night shifts, you can sleep during the day and then work out always at the same time. The trick is to keep it consistent that way your circadian rhythm adapts to it.

Over time, you will feel better and better during those workouts and it will start to feel completely normal.

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