There’s no shortage of people and products making outrageous claims about how fast it’s possible to build muscle. You might see a supplement promising gains that are on par with steroids. Then you hear about a guy who says that he put on 34 pounds of muscle in 28 days with just two 30-minute workouts a week.
Pick up any of the popular fitness magazines, and you’d be forgiven for thinking that building muscle is the easiest thing in the world. So, how fast can you put on muscle—really? The honest answer is that I don’t know. And nobody else does either. Muscle growth varies so much from person to person that it’s almost impossible to predict in advance exactly how much muscle you’ll gain over a certain period of time.
I can, however, give you a rough idea of the amount of muscle you might expect to build after several months of training hard and eating right. Knowing roughly where the natural limits to muscle growth lie will save you a lot of wasted time, effort, and money running around in search of some magic pill, diet, or training program. (More on that in a moment.) First, let’s take a closer look at some of the variables influencing your results.
The role of genetics in muscle growth
You’re in direct control of many of the things that drive muscle growth, such as how you train, what you eat, and when you eat it. But the variable with the single biggest impact on your muscle-building results is one that you can’t do a damn thing about—your genetics.
The genes you inherit obviously determine many of your physical traits, such as the color of your hair and eyes. But they also have a big impact on the speed at which you gain muscle. Some lucky folks put on muscle relatively quickly when they start lifting weights. For others, the results come much more slowly, even if they lift and eat the same.
Scientists have pinpointed many factors that influence the variability in muscle growth from person to person. They range from the number of capillaries delivering nutrients and anabolic hormones to your muscle fibers to the thickness and malleability of the connective tissue that surrounds those fibers.
One factor that’s heavily influenced by your genes are known as satellite cells. As the name suggests, satellite cells hover around your muscle fibers, waiting to be called into action to help those fibers repair and grow. While some of us have a lot of satellite cells, this doesn’t hold true for everyone. People who make rapid gains in muscle size have more satellite cells surrounding their muscle fibers, as well as the ability to expand their pool of satellite cells during training.
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In one study, a group of 66 people trained their legs three days a week for a total of four months. At the end of the study, the researchers analyzed the training logs of each subject, and found no difference in training intensity, volume, or adherence to the program. Despite this, there were wide differences in muscle growth from person to person.
“At the end of the training, the subjects fell rather neatly into three groups,” explains David Epstein in his book The Sports Gene: Inside the Science of Extraordinary Athletic Performance. “Those whose thigh muscle fibers grew 50 percent in size; those whose fibers grew 25 percent; and those who had no increase in muscle size at all.
“Even before the strength workouts began, the subjects who would ultimately make up the extreme muscle growth group had the most satellite cells in their quadriceps, waiting to be activated and build the muscle. Their default body settings were better primed to profit from weight lifting.”
In short, there are genetic factors outside your control that have a big impact on the speed at which you gain muscle. And unless you’re willing to have your genes tinkered with by a renegade scientist, there’s not a single thing you, me, or anyone else can do about it.
The role of muscle memory in building strength
Rebuilding old muscle is a lot faster than gaining it in the first place, thanks to a phenomenon known as muscle memory.
Research shows that when a muscle is gained, lost, and then gained back again, it will grow more quickly during the re-building phase compared to the initial training period from an untrained state.
Of course, muscle tissue itself can’t actually “remember” anything. Rather, the number of nuclei in muscle cells increases when you lift weights. Those nuclei, however, aren’t lost when you stop training and your muscles shrink. Instead, the extra nuclei form a type of muscle memory that allows the muscle to bounce back quickly when you start training again. All other things being equal, someone who has been in shape before will gain muscle a lot faster than someone who is starting from scratch.
The role of lifestyle in muscle growth
It’s not just the food you eat, the weights you lift, and the genes you inherit that affect your rate of muscle growth. You also need to factor in what else is going on in your life.
A training program performed against the background of a low-stress lifestyle will produce very different results to that same program paired with a high-stress lifestyle. That’s because non-training stressors have the potential to skew the rate at which you recover from and adapt to your workouts.
Researchers have found that people who are subject to greater life stress recover more slowly after training. In one study, people with lower stress scores saw greater gains in the bench press and squat after 12 weeks of training compared to people with higher stress scores.
“When athletes are subjected to elevated non-training stressors, physiological training adaptations will inevitably be compromised,” says John Kiely, former Head of Strength and Conditioning for UK Athletics. “This will occur regardless of the origin of that stress: whether it be anxiety due to loss of form, exam pressure, relationship turbulence, poor sleep, or corrosive environmental conditions.”
So let’s cut to the chase: How fast can you gain muscle naturally? If all the muscle-building stars are aligned—you’re new to lifting weights, eating enough food, lifting weights 4-5 times a week, and in your twenties with a relatively low-stress lifestyle—the average guy can hope to gain around eight or nine pounds of muscle after three months of hard training.
Some folks, despite training hard and eating right, will gain closer to 3 or 4 pounds. In some studies, one or two individuals experience a tremendous response, adding around 15 pounds of muscle. But for most people, most of the time, the results will be somewhere between those two extremes.
There is also a law of diminishing returns. Everything happens a lot more quickly when you’re a beginner. You won’t keep building muscle at the same rate indefinitely, and over time your progress is going to slow down. Over the course of a year, you’re probably not going to put on more than around 25 pounds of new muscle. Is that the absolute upper limit for every single human being that has, or ever will, set foot on this planet? No, but it's going to be close.
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