Mechanisms of Muscle Growth

By: Jeremy Partl, RD

No matter if you are at the gym, chatting with your friends out on the town, or just even scrolling through your Facebook feed, you have at some point heard the question…

“What will make my muscles grow best?”

If you…

Ask the powerlifter, and you will get the response of “it’s all about heavy weight”.

Ask the gym junkie, and you will get the response “if you aren’t sore, you are not making progress”.

Ask Arnold Schwarzenegger, and he will tell you, “you have to chase the pump”..

The truth is, the combination of all three is actually the best recipe for muscle growth.

The Recipe for Muscle Growth

 In 2010, a highly respected researcher Brad Schoenfeld, released a paper that highlighted the mechanisms of muscle hypertrophy…..or simply, WHAT MAKES MUSCLES GROW (Schoenfeld, 2010).

This article will highlight those factors and give you the practical applications to apply it straight to your training.

  1. Muscle Damage

Imagine that you wake up two days after a brutal leg workout. It seems like a normal day, but as you roll out of bed, you notice that your legs are very tight and sore. You go about your day, but as you get out of the car and head to work, you struggle to even climb the 3 steps leading into your office.

That story illustrates a phenomenon called delayed onset muscle soreness (DOMS) that is largely associated with great amounts of muscle damage. It’s important to note muscle damage it’s self does not cause growth.

What does cause the growth?

  • Cellular Adaptations- Primarily through the roll of satellite cells that become activated with muscle damage (Schoenfeld, 2010).
  • Inflammation- Once damage is perceived by the body, anti-inflammatory cells rush to the site and start cleaning up and sending signals for growth and repair to the above mentioned satellite cells (Schoenfeld, 2010).

This does not mean that your workout was not effective if you can’t walk more than a few feet without tripping.

By now you should know that a workout doesn’t always have to leave you sore to mean that your muscles are growing. There are other factors that contribute to the muscle growth process.

  1. Metabolic Stress

Remember when you had a pump so big that your arms looked like they had footballs popping out of them, or remember when you had a burning sensation feeling like somebody was stabbing you with a knife? Those are both relatable to the feeling of what we call metabolic stress.

What makes metabolic stress work?

  • Hypoxia- lack of oxygen in the muscles due to reduced bloodflow
  • Cell Swelling- pooling of the blood that causes the “pump”
  • Occlusion- restriction of bloodflow by a large number of muscle contractions
  • Metabolic Buildup- accumulation of metabolites such as lactate, hydrogen ion, inorganic phosphate, Creatine, and others.

The bodybuilder will tell you that chasing the pump and being sore is enough. However, there is one more factor that makes muscle grow.

  1. Mechanical Tension

Letting our ego get in the way, we have all put more weight on the bar, even though we couldn’t hit proper depth or execute with the right form. Our egos are driving us to create more mechanical tension by lifting heavier weights. This is one of the drivers of muscle growth, however using full range of motion and proper form should be emphasized before adding weight to the bar.

Why does mechanical tension cause growth?

  • Signaling- Increased resistance disturbs the structure of skeletal muscle, causing signals to be sent to the muscle fibers and cells to repair themselves and become stronger by favoring synthesis instead of breakdown.
  • Structure- Normally quiet cells called satellite cells that sit on the outside of the muscle fibers become active when a sufficient mechanical stimulus is imposed on skeletal muscle. Once aroused, satellite cells multiply and grow and ultimately fuse to existing cells or among themselves, providing the building blocks needed for repair and subsequent growth of new muscle tissue (Schoenfeld, 2010).

In the end, your muscles end up getting bigger and stronger.

Mechanical tension is not developed only by using heavy weights. You can create a ton of tension simply by squeezing a muscle as hard as possible and by focusing on the mind-muscle connection.

Therefore, to really make your muscle growth you want to contract your muscles under the heaviest load possible, while keeping perfect form!

If mechanical tension was the only thing that caused muscle growth, then powerlifters would be as big as bodybuilders.

Practical Applications

Now you know the science, what are the best ways to create these conditions?

Mechanical Tension

·         Adding more weight to the bar
·         Focusing on the mind muscle connection
·         Squeezing a muscle as hard as possible
·         Long rest periods to completely recover
·         Low frequency training that allows max recovery and performance from session to session


Muscle Damage

·         Slow lifting tempos
·         Weighted stretching
·         Pauses in the middle of reps
·         High amount of volume
·         Frequent changes in exercise selection


Metabolic Stress

·         Training to failure
·         Occlusion training (BFR)
·         Compound supersets, tri-sets, and giant sets
·         High volume load
·         Short rest intervals


Putting it All Together

Current research suggests that maximum gains in muscle hypertrophy are achieved by training programs that produce significant muscle damage and metabolic stress while maintaining a moderate degree of muscle tension. The general recommendations would be:

  • Use all rep ranges from 1-5 (max tension), 6-12 (muscle damage and stress) to 15+ (metabolic stress).
  • Stimulating all muscle fibers by using a using a variety of exercises in a wide range of movement planes
  • Adding volume by using multiple sets instead of only one
  • At least some of the sets should be carried out to the point of concentric muscular failure, perhaps alternating microcycles of sets to failure with those not performed to failure to minimize the potential for overtraining.
  • Concentric repetitions should be performed at fast to moderate speeds (1-3 seconds) while eccentric repetitions should be performed at slightly slower speeds (2-4 seconds).
  • Training should be periodized so that the hypertrophy phase culminates in a brief period of higher-volume overreaching followed by a taper to allow for optimal supercompensation of muscle tissue. (Schoenfeld, 2010)

If you would like help in designing a program that uses the science to guide your training, take a look at our services page.

We offer affordable coaching that will take level up your health and fitness while taking the stress off of you. Instead, you can just sit back, execute, and learn how to properly design your own program.


Schoenfeld, B. J. (2010). The mechanisms of muscle hypertrophy and their application to resistance training. The Journal of Strength & Conditioning Research, 24(10), 2857-2872.