Everyone has their own theories and preferences about the “best” time of the day to exercise. Some people, such as 5-time Mr. Universe Bill Pearl, like to get up early and finish their workouts before dawn. Others prefer to exercise in the late afternoon or evening.
Measures of muscular performance (such as strength and power), as well as hormones (like testosterone, cortisol and growth hormone) have their own unique rhythm or timing pattern, where there are low points and high points over the course of a day.
But does any of this really matter? Are you going to build more muscle and lose fat faster if you train in the morning or the evening? Is the time of day that you exercise really that important?
As a rule-of-thumb, most people seem to be strongest in the afternoon or evening. And most of the studies I’ve seen also show that muscle strength wanes in the morning and gradually improves until it peaks in the early evening.
This study found that power output during 10 x 6-second cycling sprints was higher during sprints 1,2, and 3 in the afternoon than it was in the morning. Another cycling study found that various measures of muscle power were around 8% higher in the early evening (6.00pm) compared to the morning (6.00am).
Research published in Medicine and Science in Sports and Exercise has also looked at the effect of time of day on muscular performance in a group of untrained men in their early twenties.
Each man performed a series of strength tests at 8:00am, 12.00pm, 4.00pm, and 8.00pm. Muscle performance was greatest in the evening, but only during the exercises that involved faster movements.
Studies of older men show similar results. In one trial, ten older men with an average age of 76 performed a series of strength tests at 8.00am, 12.00pm, 4.00pm, and 8.00pm.
Similar to young men, the older guys were weaker in the morning than they were in the evening. Of 36 muscle function tests, performance was least impressive at 8.00am in 26 of the tests.
“Simply stated, in an aged system, the peaks and nadirs occur at the same times as they do in a younger system,” say the researchers, “but these highs and lows are not as pronounced as those observed among the young.”
In other words, the extent to which performance differs between the morning and evening is not as pronounced in older as it is in younger men
Why was performance greater during the faster, rather than the slower movements?
The activation of fast twitch muscle fibers — which are called into action when force requirements are high — is preferentially enhanced at a higher body temperature, which tends to peak in the early evening
If your workouts involve a lot of strength- or power-based movements, chances are you’ll perform a little better in the evening than you will in the morning.
But this doesn’t apply to all forms of exercise. The authors of this study, for example, found that performance during low-intensity steady-state (LISS) exercise (such as walking or cycling) isn’t affected by the time of day.
Hormones such as testosterone (an “anabolic” hormone) and cortisol (a “catabolic” hormone) also vary during the day.
Testosterone, for example, peaks in the morning and drops at the end of the day. However, while resting testosterone levels reach a low point in the evening, the rise in testosterone after exercise appears to be greater in the evening than it is in the morning.
Resting levels of the hormone cortisol are also higher in the morning and lower in the evening. But the cortisol response to exercise is lower in the early evening (7.00pm) compared with the morning (7.00am).
In other words, the testosterone-cortisol ratio (when testosterone levels are highest relative to cortisol levels) is higher in the early evening than it is in the morning.
This, in theory at least, makes the evening the least “catabolic” time to train. I say “in theory” because short-term changes in hormone levels don’t really tell us an awful lot. So let me cut to the chase and get to the question that you really want answered:
Are you going to build more muscle and lose fat faster if you train in the morning or the evening?
One study, presented at the 2005 National Strength and Conditioning Association’s annual meeting in Las Vegas, attempted to answer this very question.
A group of 16 men trained for 10 weeks either before 10.00am (AM group) or after 6.00pm (PM group). Workouts consisted of 45 minutes of weight training followed by 45 minutes of cardiovascular exercise.
The PM group had a 3.2% increase in lean mass, compared with a 0.6% gain in the AM group. Body fat dropped by 4% in the PM group, while it actually increased by nearly 5% in the AM group. However, none of these changes was sufficient to reach statistical significance.
At first glance, these results support the idea that training in the evening works better than training in the morning.
The problem here is that studies presented at conferences are often poorly controlled, and there’s usually little or no information available about how the research was done.
This study, for example, was done at the University of Southern Mississippi. I’m guessing that the subjects who took part were also students at the university.
Based on my experience of students, a lot of them are still asleep at ten in the morning. Maybe the AM group didn’t make much progress because most of the subjects skipped the workouts and stayed in bed. Perhaps they were all so tired that they just went thought the motions before sinking their face into a plate of pancakes for breakfast.
Lead researcher Tim Scheett refers to the effects that he observed as “small” and did not regard them as big enough to discourage people from training in the morning.
“You should train at a time that is most convenient to you and at a time which feels comfortable”, stresses Scheett.
A similar study, this time from researchers based in Finland’s University of Jyväskylä, also shows slightly greater gains in muscle size when training was performed in the evening.
For the first 10 weeks of the study, subjects (a group of young men) trained between 5:00pm and 7.00pm.
The men were then assigned to a morning or afternoon training group. The morning group trained between 7:00am and 9:00am, while the afternoon group did their workouts between and 5:00pm and 7.00pm. Both groups followed the same training routine.
The size of quadriceps femoris, a muscle in the front of the thigh, was measured using a magnetic resonance imaging (MRI) scan at week 10 and 20. Muscle strength was also tested at week 0, 10, and 20 at a randomly given time of day between 9:00am and 4.00om
Although all the men gained size and strength, there was no significant difference between groups.
However, a closer look at the results reveals that the average muscle gain in the men who trained in the afternoon was 3.5%. But in the men who trained in the morning, it was only 2.7%.
Statistically speaking, this wasn’t a big enough difference to register as a “significant” result. Maybe if the groups had been bigger, or if the training program had lasted for a longer period of time, we would have seen more of a difference.
Does this mean that training in the morning means that you’ll make slower progress?
Not necessarily. For the first 10 weeks of the study, the men trained in the afternoon. If you’ve ever tried moving from an evening workout to a morning one, you’ll know that it can sometimes take a few weeks before your body gets used to the change in routine.
There is a phenomenon known as temporal specificity, which means that muscular strength will adapt and be highest when tested at the time of day when training occurred. Or to put it another way, consistently training in the morning will improve your performance in the morning.
If all the men had started out by training in the morning, which would have given them 10 weeks to get used to it, we might have seen a very different set of results.
Something else that you’ll need to take into account when deciding on the “best” time of day to train is your chronotype.
According to some studies (such as this one and this one), “owls” (evening chronotypes) are more alert during the evening, while “larks” (morning chronotypes) are more “alert” in the morning.
If you’re an Owl, you could see better results by training in the evening, while Larks might make faster progress if they train in the morning.
Personally, I’ve trained at virtually every hour of the day, though I much prefer to get it done in the morning. Even though I feel slightly weaker at this time of day, the benefits of morning exercise (for me, anyway) far outweigh the downsides.
Firstly, the gym is quieter, so I don’t have to wait around to use the equipment. Morning exercise also gives me more energy and brightens my mood for the rest of the day.
However, when I was studying at University (and working a full-time job at the same time) I would often train around midnight, simply because that was the only time I could fit it in.
If you want to get in shape and stay that way, exercise will need to be something you do most days of the week for the rest of your life. And there’ll be times when you won’t be able to match your circadian rhythms to your workout schedule, or set records every time you train.
Ultimately, the best time of day to exercise is the time of day that works for you. If you consistently exercise at a particular time of day, your body will adapt and that will eventually become the “best” time of day for you to exercise even if it wasn’t at first.
It’s a lot more important to work hard and be consistent than to waste time and energy second-guessing whether you’re training at the “right” or “wrong” time of day.
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