If you go to the gym regularly and lift weights you are most likely interested in building some nice muscle.
But do you know the principles or underlying mechanisms for the growth to actually occur?
You probably already have the basic idea of how to do build muscle mass.
I can imagine it being something like this: lift some heavy weights in the gym, eat a lot of good food and have plenty of rest.
While that is a good starting point you could face a number of issues with this simplistic idea.
In this article, you will learn the underlying mechanisms of the muscle growth you see after going to the gym.
There are many muscles in your body but I am of course talking about the muscles we think about when going to the gym i.e. skeletal muscles.
Knowing the mechanisms that stimulate muscle growth could not only satisfy your intellectual curiosity but also prevent you from making mistakes in your training.
The Different Types Of Muscle Fiber
Muscle fiber is an interesting thing to take a closer look at because the muscle and muscle fibers don’t really look like what you imagine when you look at your muscles from the outside covered in skin.
Muscles consist of long thin fibers that are bundled together with some connecting tissue around.
These long thin fibers can contract which is how you are able to push, pull, press, pinch etc.
Type I and Type II
Typically, muscle fibers are put into two different categories because of their different qualities.
They are often conveniently referred to as type I muscle fiber and type II muscle fiber.
Type I muscle fiber is known for being slow but resilient to fatigue (a.k.a. slow-twitch muscle fiber)
Type I muscle fiber is known to have a smaller potential for growth.
The type II muscle fiber, on the other hand, can produce an incredible amount of power but quickly fatigues (a.k.a. fast-twitch muscle).
Type II muscle fibers also have a much bigger potential for growth and grow faster.
Muscles In Your Body
The muscles in your body are comprised of a varying degree of type I and type II muscle fiber. This can be different from person to person and is most likely a genetic thing.
You can’t convert type I to type II or vice versa through training or anything like that, but you can stimulate the growth of each through different kinds of training.
Generally speaking, training high-rep with low weight stimulates type I muscle fiber more, and training low-rep with high weight stimulates type II muscle fiber more.
The Three Ways To Stimulate Muscle Growth
Putting physical stress on your muscles with various training is what stimulates potential muscle growth.
I say “potential” because you should always remember that the training only provides the stimulus for muscle growth.
It is the things you eat that provide the nutrients and the time you rest after which are really where the growth occurs (more on this below)
There are different ways you can structure your training to promote muscle growth, but they all more or less work due to these three mechanisms.
You can think of them as distinctive mechanisms that can be emphasized differently in your training, but they will all work together – not isolated.
1. Progressive overload / progressive tension overload
Both names describe the same thing and are essentially progressively increasing the tension in your muscle fibers.
In order to continuously grow you have to keep putting more stress on your muscles.
The muscles adapt to the level of tension and if there is no increase there is no further adaption and no muscle growth.
Often times, the most practical way to do progressive overload is incrementally increasing the weight you lift which is easy to do with barbell exercises. If that is not available you can adjust the movement a bit, e.g. by doing a push-up progression.
However, you can also progressively overload by increasing the total amount of work you do every workout (training volume) or you could increase the frequency you train every week.
For long-term progression, you have to tweak all three things.
Training volume is a term for the overall work being done and include reps, sets, and the number of exercises. Sometimes it also includes the weight being lifted and is referred as volume load.
Research shows that progressive overload is by far the most important thing to promote muscle growth.
You can read more about it in my article on reps and sets for strength training.
2. Muscle fatigue / Metabolic stress
This is essentially when you push your muscle to their energy limits.
If you feel the burn or pump you are likely experiencing metabolic fatigue.
Training to failure will surely cause metabolic stress and that kind of training can have some advantages, but it should probably be used sparingly.
3. Muscular Damage
This is the actual damage to your muscle fibers caused by exerting the high level of tension needed to perform the lift.
The damage requires repair and once the repair is done the muscle fiber is a little bit better to handle stress in the future.
Muscle damage does not necessarily lead to soreness, but it could be a likely explanation if you are more sore than usual.
The Two “Types” Of Muscle Growth (Hypertrophy)
Above I have talked about the different ways to stimulate muscle growth.
You can also say that there are two different ways for that muscle growth to occur.
Muscle growth or muscle hypertrophy as it is also called are often divided into:
1) myofibrillar hypertrophy which is more or less size increase of the muscle fibers, and
2) sarcoplasmic hypertrophy which means an increase of the fluid in the muscle cells and the storage of glycogen (energy) to be used by the muscles.
Both are associated with an increase in muscle size, but myofibrillar is related to increase in strength while the sarcoplasmic hypertrophy is more endurance related.
There is still controversy around these two classifications of muscle growth and whether sarcoplasmic hypertrophy is something in itself.
It has been used to explain why bodybuilders have much bigger but “weaker” muscles compared to powerlifters.
However, some view increase in the sarcoplasmic fluid as just a byproduct of myofibrillar hypertrophy.
The truth is that Myofibrillar and sarcoplasmic hypertrophy are closely connected and in reality, none will increase without the other.
However, with different training one or the other can be promoted.
Most people are focusing on increasing size of muscle fibers and that is what I would recommend you do as well.
When Muscle Growth Actually Occurs
The actual muscle growth happens during the recovery period after you have done your workout.
Put simply you don’t become stronger in the gym, you become stronger in the recovery time after the gym.
After you have finished your workout your body starts repairing or replacing damaged muscle fibers through a process called protein synthesis.
Actual muscle growth then simply occurs whenever protein synthesis is greater than protein breakdown.
Protein synthesis > protein breakdown = muscle growth
Your recovery period can take up to 48 hours or sometimes more depending on the intensity and volume of your training.
However, the rate of protein synthesis is not static. It usually peaks within about 24 hours after training and then slowly declines after that.
This should also help you understand that the idea you have to eat immediately after gym or else you will lose all your gains is wrong.
The Right Nutrition For Muscle Growth
If you want a proven nutrition set up or just want to learn more about nutrition in general, then I have a great free resource for you.
In my awesome nutrition guide and accompanying email course, I cover everything you need to about setting up your diet for muscle growth or fat loss.
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