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When You Work Out Might Affect How Much Muscle You Gain

New research sheds light on when most people should train.

by Christian Finn
Sep 24 2018, 8:51pm

Victor Freitas/Pexels

Some people like to wake up early and get their workouts done first thing in the morning. Others prefer to wait until later in the day, and go to the gym in the late afternoon or evening. But does the time of day you train make a difference to your results? Are you going to build muscle more quickly, for instance, if you train in the morning? Or is it better to hit the gym later in the day once your body has had a chance to warm up?

There are pros and cons to whatever time of day you schedule your workouts. If you want to add muscle to your frame as fast as humanly possible, however, research points to the afternoon and evening as being the best time of day to train.

Here's why. Back in 2009, a team of researchers based at Finland's University of Jyväskylä ran a very simple experiment: They rounded up a group of young men, and got them to train in the morning or evening for a total of ten weeks. The morning group trained between 7 am and 9 am, while the evening group did their workouts between and 5 pm and 7 pm. Both groups followed exactly the same training program, which involved lifting weights two to three times a week.

Although the difference in muscle growth didn’t reach statistical significance, subjects who trained in the evening saw their muscles grow more quickly than the group who trained in the morning. In fact, the evening group increased the size of their thigh muscles, on average, 30 percent more than their counterparts in the morning group.

A follow-up study, this time lasting six months, showed similar results. Men who trained in the morning saw their quads—specifically, their outer thighs—grow by an average of 12 percent. But the ones who hit the gym later in the day saw their thighs grow 50 percent more quickly.

In other words, training in the evening led to larger gains in muscle mass compared to the exact same training program done in the morning. The question is: Why? Some research shows much greater variability from person to person in the strength of the growth signals sent to muscles with a morning versus an evening workout.


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That is, lifting weights later in the day seems to produce a much more consistent rise in the various growth signals sent to muscle fibers. Training in the morning, on the other hand, leads to a more pronounced increase in some subjects, but a decrease in others. To quote the researchers directly:

“We found that early morning may induce significantly higher between-subject variation in some muscle growth- or metabolism-related signaling pathways compared to the same loading later in the day.”

In other words, training in the morning may provide an optimal muscle-building stimulus for some people, but not for others. All of which brings me to the subject of what's called your "chronotype."

Your chronotype reflects how the circadian system embeds itself into the 24-hour day, with peaks in physiology, cognition, and behavior occurring earlier or later in the day. In other words, you’re a morning person, an evening person, or somewhere in between.

Surveys show that roughly one in four of us are morning people. Another one in four are night owls. The other 50 percent of the population aren’t morning or evening-oriented, but somewhere in the middle; they’re usually referred to as neither-types.

Night owls tend to wake up and go to bed later, and also have trouble getting to sleep at night. Morning-types, on the other hand, go to bed earlier, wake up earlier and usually have a better night’s sleep.

Your chronotype can also affect the way you respond to exercise. In one study, Italian researchers report that morning-types perceived a bout of interval training to be harder in the evening than it was in the morning. Evening-types, on the other hand, felt like they were working harder when they trained in the morning.

In general, research shows that morning-types are less fatigued, perceive less effort during exercise, and tend to perform better during a morning workout than neither- and evening-types. Evening-types also need longer to get going, and don’t reach maximum performance levels as quickly after waking up as morning-types.

We still don’t know if matching your workout time to your chronotype will lead to a faster rate of muscle growth. But the research on chronotypes does raise the possibility that if you’re an evening person, you may see better results with evening workouts. Morning people, on the other hand, might make faster gains if they train in the morning.

All things considered, if you had the luxury of being able to train at whatever time of day was “optimal" for muscle growth, it would probably be the late afternoon or early evening. However, chances are you aren’t in that position, and will need to find a training time that works for you. Thankfully, your body can adapt to training at different times of day. Even though you may not feel as strong during a morning workout, for example, your body will become accustomed to it.

Research shows that repeated strength training in the morning produces time-of-day-specific adaptations. That is, if you normally perform better in the evening, consistently training in the morning will narrow the gap in performance between your morning and evening workouts.

I remember when I made the switch from evening to morning training, and it was a shock to the system. Everything felt so much harder. But gradually, over time, I got used to it. Ultimately, the best time of day to train is the time of day that works for you and fits your schedule. Timing is a lot less important than simply making it to the gym in the first place. Getting your workouts in on a consistent basis trumps most other things when it comes to getting in shape.

Christian Finn is a UK-based personal trainer and exercise scientist. He writes frequently about fitness and nutrition on his personal site, MuscleEvo.

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