Muscle growth occurs when the rate of muscle protein synthesis is greater than the rate of protein breakdown. In other words, when you break down muscle fibers through training thereby damaging them, your body goes to work repairing those damaged fibers and forming new muscle fibers.

And you know that means? Your muscles grow when they’re rested and fed, not while you’re training and wearing them out. Of course the two go together but make no mistake, without rest and proper nutrition, muscles won’t grow.

There are over 600 skeletal muscles that make up between one third and one half of our bodyweight and along with other connective tissues help us move and otherwise hold us together.  Skeletal muscles are made from strands called “myofibrils” that form muscle fibers. The goal in getting bigger muscles is to increase the size and number of those muscle fibers.

Like life in general, if you want to see signifiant muscle growth, you’ll have to progressively expose them to new challenges and put them under stress. But before we go into how to that, it’s important to grasp the basics of how muscles move to begin with.

Your Brain Moves Your Muscles

Fortunately you don’t have to be particularly smart and focused to make your muscles move. Still, your brain is highly involved in the process.

Imagine you have a stone about the size of a basketball laying in your yard. You’re hovering over it ready to pick it up and toss it aside. Your muscles are tense, your brain is doing its thing.

Your brain sends signals to motor neurons in your arms and legs as you prepare to bend over and grab the stone. When those motor neurons get those signals they activate and cause your muscles to contract enabling your to bend over and grab the stone. As you pick it up, you begin to stress your muscles (arms, legs, back) and your brain sends bigger signals to your muscles to help you continue lifting and even throwing that stone into the woods (or wherever).

Now, imagine that stone is something larger than a basketball, say a truck tire. That’s a heavy stone and you know moving it will be more challenging than moving the smaller stone. Still you attempt it. The muscles you used to move the smaller stone won’t be enough to move this one. You’ll have to “give it everything you’ve got”. Your brain will now produce even bigger signals to more motor units all across your body. As you bend to attempt to flip the stone over, muscles from your neck to your calves tense up, you strain and scream and manage to flip it over. There is much rejoicing!

The miracle of what just happened is that your nervous system took advantage of every available resource (even muscles you didn’t know you had – they’ll be sore in the morning) to rise up to the challenge of moving the larger stone. This kind of strength is often called “neurological strength” and it’s the reason you get stronger when you workout even though your muscles aren’t growing. Your brain and nervous system masterfully adapt to new challenges and stress.

Tear Up Your Muscles to Make them Grow

This seems counterintuitive. It seems like massaging muscles, nurturing them, loving them, petting them, feeding them, would cause them to grow but it doesn’t work that way. You’ve got to be mean to them!

When you put your muscles under extreme stress, in addition to all the motor neuron action, something else is happens. They undergo microscopic damage and develop micro-tears that have to heal. When these tears happen, the injured muscle cells release molecules called “cytokines” that call the immune system to begin healing your microscopically injured muscles. Let the muscle building magic begin!

The more damage done to your muscle fibers through subjecting them to greater challenges and stress, the more the body will need to repair. This cycle of damage and repair is what makes muscles bigger and stronger. Our bodies are amazing at adapting and our muscles will adapt to progressively greater challenges by getting bigger and stronger.

Progressive Overload or Die

Our normal daily activities don’t challenge our muscles enough to stimulate new muscle growth because our bodies have already adapted to those challenges. This is especially true if you work in an office setting where the most difficult physical task you’ll face is loading paper in a copier but it even applies to the construction worker who regularly hauls hundred pound bags of concrete. In order to build new muscle, a process called “hypertrophy”, muscle fibers need to be challenged with greater and greater loads than they’re used to. In fact, if you don’t do this on a consistent basis your muscles will atrophy or shrink as you get older (more so for the office worker than the construction worker).

Exposing your muscles to greater challenges through weight training is one of the best solutions to combat muscular atrophy and is usually the preferred way to achieve muscle growth. Otherwise, if you’re a construction worker, you’d have to find some heavier bags of concrete to move. Weight training also creates a better environment to put your muscles under a high degree of controlled tension. It’s been proven that when our muscles lengthen under tension, i.e. during the “eccentric contraction” or “negative” of an exercise, optimal conditions for new growth are created. This is one of the reasons why performing 3-4 second negatives of an exercise, thereby increasing the time under tension during muscle lengthening, is recommended during weight training. Of course, you need more than just intelligent and challenging weight training for muscles to grow. Without nutrition, hormones, and rest, your body can’t repair the damaged muscles.

Muscle Repair = Muscle Growth

Progressively increasing activity, challenge, stress, muscular tension, and even weight on the bar won’t do a thing to build muscle if your muscles don’t have what they need to heal. Nutrition is the cornerstone of the muscle repair and muscle growth process and protein is the cornerstone of a muscle building nutrition plan.

Protein preserves muscle mass by providing the amino acids needed to build new muscle tissue. There’s quite a bit of debate about how much protein you need to consume and that’s probably because everyone’s protein needs are different. “Adequate protein” for me may be more or less than “adequate protein” for you. It’s best to experiment but a good starting point for most men is 150g of protein per day.

But, protein and nutrition isn’t all. Naturally occurring hormones like insulin, insulin-like growth factor and testosterone shift the body into muscle repair and growth mode. If those hormones are out of balance or not being produced at adequate levels, the muscle repair and growth process will be drastically inhibited. Likewise, if you’re not getting enough rest / sleep the muscle repair process will also be halted. The bulk of muscle repair happens while we’re sleeping so in addition to an intelligently designed workout and nutrition plan, a well-though out sleeping plan is important too!

Of course, gender, age, and genetics play a role in muscle growth as well. In general, young men with more testosterone are going to have a muscle building advantage (that is, it will happen quicker and easier) but men and women can build or at least preserve muscle at any age. It’s frustrating but genetic factors also play a role in one’s ability to grow muscle simply because some people have better immune muscle repair reactions. That is, they’re better able to repair and grow damaged muscle fibers. Steroids aid in the muscle repair process too which is why they’re heavily used in the body building world. Don’t let age, gender, or genetic factors stop you! Work with what you’ve got and continue to challenge your muscles, eat right, and rest consistently and you’ll provide your muscles with the right environment to grow as big and strong as possible.