What Causes Muscles to Grow

There are a million articles and programs offering up the next secret (aka, gimmick/fad/farce) method for packing on tons of muscle. Rather than give you some, “top secret” approach or quick tip that will have you spinning your wheels in the gym, I’d rather explain to you the overall concept of what has to happen for you to add muscle mass to your frame. As an overall concept, what I would like to get across to you in this article is that the human body doesn’t want to put on muscle mass.You have to make a conscious decision to do something that is incredibly uncomfortable and jarring to your organism so that you give your body no other choice but to pack on more muscle so that it can defend itself from the same stressor if it is encountered again. Gaining muscle mass is hard work that never ends. Following the application of significant stress to your body, you need to recover. The recovery period is where you add new proteins to your muscles so that they become bigger and stronger. As un-sexy and not new as it sounds, if you want to gain muscle mass, you’re going to have to work very hard in the gym and live a healthy lifestyle outside of it featuring appropriate sleep, nutrition, and hydration. If you understand the big picture and why things have to be done a certain way, perhaps you will be more willing to actually do it.

The Captain and The Ship

Think of a ship out on the open ocean. The ship encounters a storm. Driving winds and rain wreak havoc on the deck while the hull is getting pounded by enormous waves. The ship survives this storm, but it took on significant damage. The captain of the ship looks around in the aftermath and sees a broken mast, holes in the sidewall, and a few steady leaks. If he wants to keep sailing in these waters he’s clearly going to have to make some repairs and perhaps revamp this boat.

He analyzes the damage of the ship and sees which areas were most impacted by the storm. He reinforces those areas. He puts up a thicker, sturdier mast, makes the sidewalls denser, and shores up the leaks with a stronger adhesive material. The ship goes back out on the ocean, and another storm comes along almost exactly like the first one. The ship survives this storm with only minimal damage. All the areas that the captain focused on for repairs held up pretty well.

Photo Credit:  Todd Kumpf
Photo Credit: Todd Kumpf

The next day he and his crew patch the ship up a little bit and it’s ready for the open ocean again. This time a completely different storm is encountered. Freak snow comes out of nowhere, icy seawater sloshes over the sides of the boat, and chunks of debris come flying through the air, shredding the ship. The crew and the vessel make it, but this time the damage is completely different compared to the first storm. It was as if nothing the crew had done in their repairs following the first storm had prepared them for this last squall. The captain orders the crew to go back to work the next day. They focus on the areas that were most heavily damaged in this last disaster and rebuild those sections with more robust material.

Do you think the captain and crew of our imaginary ship want to spend their days laboring to rebuild their ship? Of course not. All they want to do is to continue to sail so that they can do their jobs so they can put food on the table. They would never put in the effort to work on the ship unless it was very clear that the ship was unfit for use and that it needed to be strengthened to handle similar difficult demands again in the future.

Do you think they’re going to fix and rebuild parts of the ship that were unharmed from the storm? Of course not. You focus your attention on the areas that need help. Can you fix every part of the ship all at once? Probably not, you have a limitation to the size of your crew, and they can only work so hard for so long. You also do not have unlimited amounts of wood, tools, and other assorted pieces to be able to repair everything all at once. Ultimately, you have to decide what kind of storm you want your boat to be ready to handle. You simply can’t have it all. You also can’t permanently live in the storm. If you’re going to be fixing your boat, you should probably do it when it’s sunny and you’re safely docked.

Your body is the boat. The captain is your brain. The crew is your immune and endocrine systems working to trigger the appropriate cellular repair steps. The wood and the tools that you use for repairs is the food you eat, the water you drink, and the sleep that you acquire. You have to figure out what kind of storm is the appropriate kind in order to trigger the appropriate repair process that will build you a new body that is more muscular than it was before. Obviously running a marathon is an absolutely ungodly storm that you could encounter, but the repair mechanisms that would take place after wouldn’t be geared towards adding muscle to your frame. The storm has to be highly specific. The raw material also has to be of very high quality that you use to repair yourself after the fact. Do you want to be going into your next storm on a boat made of rotting wood, or do you want only the finest, most outstanding construction material possible for your vessel?

The Perfect Storm

What is the perfect storm for creating the optimal stimulus for growing muscle? It primarily comes down to three variables. It seems as though the combination of mechanical load, heat, and acidity is the right environment for optimizing muscle growth.

The research in this area seems to indicate that multiple sets (3-5) of approximately 10 repetition maximum (RM) load using multi-joint compound exercises (squatting, bench pressing, deadlifting, pull-ups) with short rest (approximately 60 seconds) is optimal for increasing muscle mass. Go ahead and try doing 5 sets of 10 (with a weight where you couldn’t get 11) in the squat with 60 seconds rest in between. You’re going to be hot, acidic, and your muscles will be dead. You just hit the perfect storm.

Your brain will register this event and trigger all of the cascade responses driven through the hormonal and immune systems associated with repair and growth of skeletal muscle that you can muster up as an organism. You could do this kind of workout over and over again for a pretty substantial period of time and continue to get great gains for a while. The problem with that exact workout is that it’s pretty boring at a certain point, and even if you were the most diligent person, who cares nothing about routine and boredom, at a certain point, your body would adapt to this, and you’d stop making any headway. You need to vary things up a little bit to keep yourself engaged, and to force the organism to have to adapt to a salient threat. The thing is, you don’t want to vary things up so much that it’s a completely different kind of storm. If the storm is wrong, then the repairs will be to create a different kind of ship. If the challenge to the body isn’t appropriate, it might strip material away rather than add on.

Closing Thoughts

To finish off this article, you need to understand the following things about the storm and the repair process. Feeling a fairly heavy weight, feeling hot, and feeling an acidic burn are the three threats that drive the muscle building train.

When it comes to driving adaptation, you need to scare your body…so threaten it the best you possibly can. Sets between 6 and 15 reps are probably the most appropriate for hypertrophy, with sets of 10 being most optimal. Rest periods need to be kept short to create the truly significant heat and acid load response. If you’re using the same exercise over and over, look to stay within 60 to 90 seconds of rest. If you’re setting up a circuit, you’ve got a little more leeway, and you can make the rest periods shorter.


Work really hard, but when you’re done, make sure you recover appropriately. Earlier I talked about fixing the boat in sunny skies and calm seas. Here’s my recommendation for sunny skies and calm seas in life. Most importantly, have a good relationship with family and friends. Spend time with other people. Social engagement will trigger the parts of your brain associated with relaxation, regeneration, and recovery (specifically the nucleus ambiguous component of the parasympathetic nervous system located in the medulla). Second, if you’re going to do recovery exercise, do easy cardio. Try to get outdoors to soak up some vitamin D. You don’t want to try to create a whole new storm environment to fix your ship in. Light cardiovascular exercise increases circulation (gets the repair pieces to the tissues), and increases the amount of mitochondria in your body. Mitochondria are the location where you utilize oxidative rephosphorylation of ATP. If you’re using your oxidative energy system, it allows the muscle tissue to relax in that location. Being able to relax and hit the off switch is critical when it comes to repair and growth.

When it’s time to be in the storm, make it the perfect storm. The storm should be hell. See what you’re capable of surviving. Load the bar up pretty heavy. See what you’ve got. Push through those last couple of reps. Keep your rest short…feel like you’re going to die. When the storm is over, shut it down. Relax. Enjoy other people that you really like. Eat, drink, and be merry. Do a little recovery work between storms. Make sure you don’t have to recover from your recovery work. I wish you well young sailor. Hopefully your vessel is sound and your captain is wise. Keep sailing, I’ll see you in Gainsville if you stay the course.

If you're into this whole muscle thing, then be sure to checkout Pat's new e-book MASS.  It gives you 66 pages of awesome info coupled with a 16 week training program designed to build muscle.

about the author


pat davidson

-Director of Training Methodology and Continuing Education at Peak Performance, NYC.

-Assistant Professor at Brooklyn College, 2009-2011

-Assistant Professor, Springfield College 2011-2014

-Head Coach Springfield College Team Ironsports 2011-2013

-175 pound Strongman competitor. Two time qualifier for world championships at Arnold Classic

-Renaissance Meat Head