How Long Does it Take to Build Muscle?

An expert personal trainer explains the different factors that effect muscle growth

How long does it take to build muscle?

The simple answer to this question, like with most fitness-related queries, is that it depends, and there are a lot of different factors that come into play.

Rate of muscle growth depends on age, gender, training age, genetics, and hormonal profile, along with other factors,” says Marc Perry, founder and CEO of BuiltLean and a top personal trainer and fitness expert in New York City.  “A 20-year-old man who has just started lifting weights who has normal muscle-building genetics might be able to gain two pounds per month on a quality muscle-building program, then after a year the number might go down to one pound per month, then dwindle from there as the man begins reaching his maximum muscle potential without the use of ergogenic aids like steroids. “

He went on to explain that other genetic factors, like your bone structure and the percentage of fast-twitch Type 2 muscle fibers that you have, which grow larger in size than slow-twitch Type 1 muscle fibers, all play a role in determining at what pace you’ll be able to build muscle.

“You can think about muscle building potential like a normal bell curve,” Perry said. “Most people will be able to gain muscle with some effort, whereas some will have a very tough time and others can gain muscle very easily.”

According to Perry, when it comes to muscle growth, training age, or the amount of time you’ve spent effectively training, is usually the most significant determining factor.

He explains, “If you take a 16-year-old man who has no exercise experience, he may gain 20 to 25 pounds in only a year, but after that the rate of muscle growth may slow down substantially.  By the time someone is a mature lifter, that person may only gain one half of a pound per month if he, or she is lucky.”

Speaking of luck, when it comes to building muscle, some might say that females got the shorter end of the stick.

Perry said that compared to men, women have a less advantageous hormonal profile for muscle growth.

“Women on average have only 5 to 10% of the muscle-building hormone testosterone as men,” he said. “In addition, research shows women tend to have less musculature than men, especially in their upper bodies, and are roughly half as strong.”

However, Perry points out a study from 2005, which revealed that relative muscle growth for men and women is the same, but that women may typically experience a larger relative increase in strength.

“The operative word is ‘relative,’” Perry said. “Because women are not as large as men so the amount of muscle gained will be less despite a possibly similar rate of muscle growth.”

For those who are training with aims to increase muscle mass, Perry suggests measuring your progress with body fat calipers and a bodyweight scale. Record your body fat percentage and your bodyweight, then use those numbers to determine how many of those pounds are fat.  

“What's left over is your lean body mass,” Perry said. “Which includes everything else such as muscle, bones, water, and blood. 

He offered the following example:

If a 160 pound man has 20 percent body fat, he has 32 pounds of fat and 128 pounds of lean body mass.  If two months later he weighs 170 pounds at 22 percent body fat, he now has 37 pounds of fat and 133 pounds of lean body mass, which means he gained 5 pounds of muscle and 5 pounds of fat in those two months.

And as far as what it takes to successfully build-muscle mass goes, Perry says that once again, many factors come into play.

Effective weight-lifting strategies that he says are supported by research include: a 6 to 12 repetition range, allowing for 60 to 90 seconds of rest between each set, performing multiple sets per each exercise, performing different exercises that target given muscle groups for maximum muscle stimulation (or what he referred to as a “multi-planar approach”), and a split training routine that emphasizes specific muscle groups during each workout.

“My favorite exercise for building muscle is undoubtedly the barbell back squat using moderate to heavy weight,” he said.