Getting Swole: What Makes Muscles Grow?

what makes muscles grow

Have you heard? Muscles are totally in right now! And it’s a trend that I’m absolutely loving. More and more women are getting serious about strength training and I couldn’t be happier about it. We should all be paying far more attention to our muscles.

Each of us is made up of about 650 muscles — pause to let that sink in — that’s 650 individual muscles all designed to serve a unique function to allow us to move, stand, eat, talk and breathe. All day long they do their respective jobs and you don’t really have to think much about it, but it’s amazing when you do think about it. We really are magnificent creatures.

Our bodies are also incredibly adaptive. They learn to deal with stress using the least amount of energy possible. In other words, your body becomes remarkably efficient at dealing with your routine. At this very moment in time, you’ve got exactly the right amount of muscle tissue to deal with your everyday life. So if you want to create change, you’ve gotta shake things up.

Wondering how to pack on more muscle? Pull up a chair.

The Science in Plain English

If you want your muscles to grow, you’ve gotta give them a reason, meaning that you need to apply stress to your muscles that is  greater than what they’re used to dealing with — either by adding more weight, moving through a bigger range of motion, doing different exercises, taking less rest breaks or adding more reps. Every time you apply a new or bigger stress to your muscles, they’re forced to respond and adapt.

When a muscle is stressed beyond its current capability, the individual fibers that make up the muscle are damaged. This triggers an inflammation response and your immune system activates special cells in the muscle called satellite cells, which move into the damaged area, multiply and then fuse themselves to the damaged fibers. These newly repaired fibers are stronger and more resilient than the old ones — think of it as your muscle’s insurance policy to avoid future damage just in case you ever decide to stress it out like that again.

These new thicker fibers are what makes the muscle grow is size. The greater the stress, the greater the damage and the greater the potential for muscular growth. Notice I said “potential” for growth.

This system is awesome assuming that you help the repair process along and allow it to complete before you damage those fibers again. Your ability to grow bigger and stronger muscles is very much dependent on your ability to recover and regenerate the damaged muscle tissue.

Regeneration and repair only happen when you rest and consume the building blocks (carbs and amino acids from protein) needed by your body to fuel the satellite cells and grow new muscle tissue.

The repair process peaks around 24-36 hours after the damage was caused and may continue for as long as 72 hours after — this is why post-workout muscle soreness can take a day or two to show up.

The Bottom Line

In order to accomplish muscle growth, the rate of tissue repair must be greater than the rate of tissue damage. So it’s not all about the workout — in fact, if you’re working out hard, you need to be recovering even harder. Muscles don’t actually grow during your workout — they’re only damaged. Muscle growth only occurs when the muscle is repaired.

Without proper rest and the necessary nutritional building blocks, your muscles will break down and you’ll lose muscle despite your best efforts in the gym. Skeletal muscles are the most adaptive and resilient tissues in your body but they need your help.

Keep in mind that too much stress or insufficient repair will likely lead to injury — and nothing kills goals faster than injuries. So push yourself but be smart about it and follow a progressive overload program where the stress is gradually increased over time with adequate rest and nutrition for muscular adaptation and growth.

Who’s ready for some post-workout jerky and a nap? —Alison


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  1. I appreciate how you broke this down, Allison. I think one of the most important points you make is about changing the positive stress on muscles to get them to grow. When I train clients I often tell them that in order to change something, something has to change.

    I’m curious – do you think the rest period should vary based on the activity and type of load put on the muscles? For example, would a weight-training workout require more recovery than a movement workout (like dance) in terms of building muscle effectively and safely? Does it tend to vary person to person?

    Thank you for your clear and insightful article.

  2. I too really appreciated this article. I am not a professional, but have read articles about exercising and strengthening muscle and the importance of recovery. I like the phrase you used “Muscles don’t actually grow during your workout — they’re only damaged. Muscle growth only occurs when the muscle is repaired” those words really hit a home run with me on the importance of recovery. The paragraph following that phrase put it all together for me and helped me understand muscle recovery even more. Thank you for this insightful article!

  3. Alison – Thanks for the post, well appreciated. what about the diet? if I eat right food, will I get the muscle growth without doing exercises?

  4. Thanks for this great article Allison. This is really helpful in breaking down the process of muscle growth and I love how you stress the idea of recovery. To build muscle many people don’t realize the recovery stage as well as the right type of eating is just as important as the workout and many solely focus on their workout which only makes it more difficult to build muscle.
    We really enjoy your blogs and website keep up the great work! If you would like to check out our website and product.

  5. Awesome post you share on this page ,After reading your information i find the safety solution of burning a body fat and lifting a heavy weight easily by start jogging daily in early morning and follow diet plan with the instructions of gym trainer or a doctor advice .


  6. Hey Rebecca – It totally depends on the person and how big of a challenge the specific workout was for that particular individual. Age, other physical activity, genetics, body weight, and diet, among other factors, definitely play a role. Rule of thumb: the greater the challenge, the greater the damage to the tissue — which would mean more recovery is needed for healing. Cardio/movement is typically less strenuous for skeletal muscles (which is why people can do it for longer periods of time without needing to rest the muscles being used) than strength training (assuming the weights are heavy enough to sufficiently challenge the muscles that are doing the work) but it would depend on what the person is already used to. Hope this helps. -Alison