Inflammation: the major regulator of muscle growth nobody talks about

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Inflammation is often regarded as something bad you need to suppress. That reputation is entirely unjustified and treating inflammation this way can directly reduce your muscle growth. In this article we’ll cover the relationship between inflammation and muscle growth and several important practical applications. If you like this article, you’ll love our online PT Course, as this article is an excerpt thereof.

We’re also writing up a full scientific review on the relationship between inflammation and muscle growth, so consider this article a primer for more to come.


What is inflammation?

Much like cortisol, inflammation has a reputation of something inherently bad, yet it is required for your body to function and has many desirable effects. Inflammation is effectively a signal for the immune system to pay attention to an area. Inflammation is part of the immune system’s response to fix tissue damage and get rid of things that don’t belong in an area, like viruses. Inflammation thus occurs in response to an infection, but inflammation isn’t limited to infections. So it’s incorrect that some languages, like Dutch, use the word infection for all inflammation. The lack of a word for inflammation in Dutch is a perfect illustration of how neglected a topic inflammation is.


What does inflammation have to do with muscle growth?

Strength training induces a considerable amount of inflammation in muscle tissue as a result of the damage to the muscle fibers. This inflammatory signaling initiates muscle repair and growth.


Interleukin-6 (IL-6) is a key player in the inflammatory regulation of muscle repair. Interleukins are cytokines: small proteins that act as signalling molecules. IL-6 is interesting in that it can act as both a pro-inflammatory cytokine in the blood but also as an anti-inflammatory myokine in response to muscle contraction.


Whether IL-6 is pro- or anti-inflammatory depends on its concentration and whether it was stimulated by muscle contraction or fat tissue. High resting levels of IL-6 indicate chronic inflammation, a generally undesirable condition that leads to erosion of many tissues as a result of an overactive immune system (auto-immune). Chronic inflammation has been linked to joint injuries, low testosterone levels and an impaired ability to gain muscle.


In a 9 month study on postmenopausal, strength training women, trunk fat mass correlated with resting IL-6 levels and negatively correlated with muscle growth. The more chronic inflammation the women had, the less muscle they gained.


Chronic inflammation, as measured by elevated C-reactive protein, also negatively correlated with muscle growth in a study of hospitalized elderly performing strength training.


Elevated pro-inflammatory gene expression has also been found to occur during overreaching and was associated with reduced muscle growth compared to training with less volume.


Non-responders to strength training, individuals that don’t make any gains from a training program, have been found to have increased inflammation (TNA-a) levels. So if you’re not building any muscle, that may be because of excess inflammation.


Based on these findings, you may conclude: “Ah, see, inflammation is bad for everything, including muscle growth, so we need to suppress it!” Yet acute spikes in IL-6 are beneficial to activate satellite cells and start muscle repair. So IL-6 has a dual nature for muscle growth that corresponds with its dual nature in inflammation: short elevations are good but long ones are detrimental. This dual nature of IL-6 is perfectly illustrated in a 4 month study on young, strength training men from Mitchell et al. (2013): resting IL-6 levels negatively correlated with muscle growth but post-exercise elevations in IL-6 positively correlated with muscle growth.


Brad Pilon hypothesized that inflammation has a signal-to-noise relation with muscle growth. Inflammation is in principle a signal for muscle repair, but chronic inflammation drowns out the acute signal.


Inflammation signal to noise


This dual nature of IL-6 is not unique. Cortisol functions similarly when it comes to fat loss: short, acute spikes are beneficial to mobilize energy, yet chronic cortisol elevations disrupt a multitude of systems in the body that generally interfere with fat loss attempts.


Because of the dual nature of inflammation with acute elevation being beneficial but chronic elevation being detrimental to muscle growth, we want low resting inflammation levels with clear post-exercise spikes to start muscle growth. This has many applications for your training, nutrition and supplementation. We’ll go into 2 relatively underrated ones below.


Practical application 1: Don’t bulk at too high a body fat percentage

Chronic inflammation levels are strongly linked to your body fat percentage: the more fat you have, the more inflammation you have [2]. Fat tissue itself secretes pro-inflammatory cytokines. Because blood sugar is inherently inflammatory, insulin resistance caused by a high fat level, especially high visceral fat storage around the liver, further contributes to the effect of body fat percentage on chronic inflammation. The increase in IL-6 levels at higher body fat percentages can be 2-4 fold, which is right around the elevation caused normally by strength training. The chronic inflammation will then thus almost completely mask the signal for muscle repair.


As a result, trying to put on muscle when you’re above your ideal body fat percentage range is highly ineffective and results in the notorious dreamerbulk. At the end of the subsequent cut, you find out you haven’t gained much net muscle mass at all. In my experience, this is one of the major reasons so many natural trainees are unsuccessful at bulking.


Practical application 2: Don’t needlessly suppress inflammation

A multitude of studies have found mostly detrimental effects of supplementing anti-oxidants or anti-inflammatory drugs in young exercising individuals, as this blunts the inflammatory signal for muscle repair and thus reduces muscle growth and performance gains. However, in the elderly some research found increased muscle growth, presumably because then it was more beneficial to lower chronic inflammation levels than it was to preserve the acute inflammation from exercise.


As such, you need to be wary of everything that suppresses inflammation, including the following pitfalls.

  • The American practice of taking Ibuprofen for every minor injury can hurt muscle growth (and is probably a bad idea anyway for the injury and your digestive health, but that’s another topic). If you do need to numb the pain, consider Paracetemol first.
  • Many multivitamins and pre-workouts have ridiculous amounts of vitamins C and E that have been found to blunt your gains. Check the label! Anything with more than 250 mg vitamin C is probably a bad idea if you’re healthy, especially around your workouts. Pre-workouts and multivitamins generally have a poor choice of ingredients and dosages anyway.
  • Cold therapy strategies to ‘enhance’ recovery, like ice baths, are often a bad idea if you’re not injured. Yes, they suppress inflammation, but that means you’re also suppressing the repair process. Cryotherapy can directly reduce muscle growth and performance gains.



Inflammation isn’t just something bad you need to suppress whenever possible. Inflammation is a part of muscle growth and suppressing it needlessly will thus reduce muscle growth. On the other hand, you also want to avoid chronic inflammation levels. You want low chronic inflammation combined with acute spikes from your workouts for maximum muscle growth.


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About the author

Menno Henselmans

Formerly a business consultant, I've traded my company car to follow my passion in strength training. I'm now an online physique coach, scientist and international public speaker with the mission to help serious trainees master their physique.

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