Does muscle burn lead to muscle growth?

Our primary goal is to achieve muscle hypertrophy (muscle growth). And to do so with the least amount of wear-and-tear to surrounding joints as possible. To build your muscles up without tearing the rest of your body down. We talk about connecting to your individual muscles and feeling them work during our exercises. But what does this mind-muscle connection or that “cooked feeling” really have to do with muscle hypertrophy? And can hypertrophy occur without these two variables? Let’s dive in!!

What is muscle hypertrophy?

In his Brief Review on the mechanisms of muscle hypertrophy, Brad Schoenfeld, PhD, CSCS, CSPS, NSCA-CPT describes muscle hypertrophy in the following way:

“When skeletal muscle is subjected to an overload stimulus, it causes perturbations in myofibers and the related extracellular matrix. This sets off a chain of myogenic events that ultimately leads to an increase in the size and amounts of the myofibrillar contractile proteins actin and myosin, and the total number of sarcomeres in parallel. This, in turn, augments the diameter of individual fibers and thereby results in an increase in muscle cross-sectional area”. 

He goes on to describe both the cellular and hormonal pathways that come into play when building muscle mass. And that resistance training plays a significant role in the initiation of these very pathways!

What elements of resistance training initiate hypertrophy? Is it all about the muscle burn?

There are 3 main factors that initiate this hypertrophic process:

1. Mechanical Tension 
2. Metabolic Stress (muscle burn!)
3. Muscle Damage 

The 3 “M’s” if you will. All 3 of these factors are necessary and complementary when it comes to muscle growth.

Mechanical Tension

Muscle tension is “produced both by force generation and stretch” (1). These two factors build on one another and are both very present with eccentric-based exercises. 

The eccentric portion of an exercise occurs when one loads the muscle while simultaneously lengthening it. On a cellular level, this lengthening can be described as “lengthening of extramyofibrillar elements, especially collagen content in extracellular matrix and titin” (1). This causes the passive tension within a muscle to drastically increase. Simultaneously, we can often accept more load eccentrically than we can concentrically. Meaning we can get a significant amount of force generation through the muscle while placing the muscle under passive tension. 

Exercise selection is also key here. We include exercises that place the most load through the muscle while prioritizing the eccentric component of said exercise. 

Here’s an example: 
A matrix move (reverse nordic curl) optimizes load to the quad. The lever for the quads, the tibia, is completely parallel with the ground. As we lean back into the exercise, we place a passive mechanical, stretch tension through the muscle WHILE optimally loading it. So much bang for your buck!!

Metabolic Stress (Muscle Burn)

Metabolic stress occurs with a buildup of metabolites within the muscle in response to resistance training. Remember that muscle “burning” feeling we mentioned? That’s to be expected with this buildup of metabolites! 

Exercise routines that primarily rely on anaerobic glycolysis lead to this subsequent build up in metabolites. Both repetition scheme and training to muscle failure seem to have an effect on this anaerobic glycolysis. 

Research has shown that moderate repetition schemes are more likely to operate within anaerobic glycolysis as compared to high or low rep schemes. 

Training towards muscular failure each set increases this metabolic stress within the muscle. Training to failure also allows us to activate a larger number of motor units within the muscle. This adds to its hypertrophic potential and response! 

We keep our Build exercise sets in the moderate range (60-90 secs of work). We also cue to work towards that muscle failure with each and every set of class.

But not all resistance exercise routines lead to an increase in metabolic stress. And not all activities that lead to an increase in metabolic stress guarantee to lead to significant muscle hypertrophy. So while there is research to support that an increase in metabolic stress can bolster muscle hypertrophy when appropriate mechanical load is applied, metabolic stress is not the main driver of hypertrophy!

Muscle Damage 

Exercise is a catabolic process in which muscle tissue is damaged and broken down. This breakdown sets off a cascade of events to first remove the damage followed by a signal to further build up this tissue. 

Specifically, Satellite Cells, thought to be “muscle stem cells”, are mobilized to build upon the muscle tissue that has been specifically damaged. 

Just as with muscle burn, eccentric training and exercise selection will play significant roles in the damage we can impart on individual muscles.

The exact effect of muscle damage on rate of muscle hypertrophy is unclear and should not be thought of as the primary stimulus for muscle hypertrophy.

It is also important to note that too much muscle damage could potentially have a negative effect on muscle growth. This is where appropriate recovery time and programming really come into play. If more damage is induced within a muscle through exercise before the muscle has had appropriate time to recover, the additional muscle damage may actually dampen the muscle-building pathways.

So how does the mind-muscle connection come into play? Is this the same as muscle burn?

The mind-muscle connection can be globally described as one’s ability to think about a muscle and subsequently contract it. For example, you can think about squeezing your glutes together and subsequently perform the necessary muscular contraction.

This relationship is modulated by the connection between neurons (nerve cells) to the muscle tissue. These two structures meet at a neuromuscular junction. A muscle’s action is completely controlled by its corresponding neuron. As in it cannot contract without a signal from the neuron to do so! The initiation of this contraction most typically happens subconsciously in the brain, travels through the spinal cord, and to the muscle tissue. No “thinking” required.

Can emphasizing or improving the mind-muscle connection actually improve muscle hypertrophy??

Yep!!!

Our ability to both contract and relax a muscle on demand can absolutely play a role in our hypertrophic training. 

An improved nerve-to-muscle relationship can allow us to recruit more motor units, just as we see when working to muscle failure! 

In his Evidence-Based Personal Training Column, Schoenfeld describes two different types of attentional focus and their potential effects on muscle hypertrophy.

• External Focus 
• Internal Focus 

External focus occurs when one thinks about their environment or the outcome of a lift or exercise while internal focus occurs when one thinks about the specific muscle they are targeting with an exercise (mind-muscle connection!). 

While external focus seems to be beneficial for performance in activities like powerlifting and athletics, it is internal focus that seems to play a more significant role in muscle hypertrophy. 
Schoenfeld states that this internal focus is shown to increase all 3 of the big M’s: mechanical tension, metabolic stress, and muscle damage. So if your goal is specific muscle hypertrophy, why not seek to improve your ability to sense the muscle you are targeting?

Does sensing or contracting a muscle alone lead to hypertrophy?

No! 

It is important to note that the mind-muscle connection in and of itself, just like the muscle burn, is not the primary driver of muscle hypertrophy. For example, just thinking about and squeezing your glutes together is not going to lead to a significant increase in glute muscle mass. 
However, pairing this mind-muscle connection with a highly-specific glute exercise (like a step up) can amplify the effects of the step up. Here at Evlo, we want you to get the most out of each and every exercise. Cueing for that mind-muscle connection while programming the most biomechanically advantageous exercises allow us to do just that!

References

1. https://journals.lww.com/nsca-jscr/Fulltext/2010/10000/The_Mechanisms_of_Muscle_Hypertrophy_and_Their.40.aspx

2. https://www.researchgate.net/profile/Brad-Schoenfeld/publication/291018876_Attentional_Focus_for_Maximizing_Muscle_Development/links/56aff17908ae9f0ff7b295ce/Attentional-Focus-for-Maximizing-Muscle-Development.pdf