The Science Behind Muscle Soreness: Do Sore Muscles Mean Growth?

Anyone who’s ever stepped foot inside a gym has likely dealt with a little post-exercise muscle soreness.  It usually comes on after trying a new exercise or having been away from your workouts for too long.

Muscle soreness is a curious thing; on one hand it makes walking, bending, lifting, or just plain living life difficult.  The pain can range from mildly uncomfortable to downright unbearable, and it seems nothing helps to make it go away.  On the other hand, muscle soreness is sometimes described as a “good pain”.  For many people it’s a feeling that they really accomplished something in the gym and their muscles are responding positively.  But is that truly what it is?  Are sore muscles a sign that you made great progress in the gym and your muscles are growing back bigger and stronger?

Today, we take a look at the science behind muscle soreness and fill you on the age-old question; ” Are sore muscles a sign of muscular growth?”


What Causes Muscle Soreness?

Conventional wisdom would lead us to believe that a build up of lactic acid in the muscle was the culprit for all of that post-exercise muscle soreness. New research however has led us to believe this is not the case.

The real reason for muscle soreness has to do with the immune response and inflammation.  When we work out a new muscle, we cause microscopic damage. The immune system responds to this damage by ramping up immune cell production.  These cells are what lead to inflammation.  Not only that, these immune cells will signal nerve endings more sensitive [1].  These now highly sensitive nerve endings are found in the connective tissue which holds our muscles together.  When we bend, stretch, and otherwise activate the muscle, the connective tissue with our sensitive nerve endings send the signal of “soreness” to our brain.

So in reality, it’s out connective tissue, not the muscle itself that is producing that “sore” feeling after a hard workout.


Does Muscle Soreness Mean You Made Progress?

As we mentioned above, going to the gym and doing something your body is unfamiliar to may very well cause a bout of muscle soreness.  But does that mean you’ve necessarily made progress? i.e. your muscles will grow back bigger and stronger.

Not necessarily.  Scientists have concluded that muscle damage does not always equate to muscle growth.  One such study examined two groups of exercisers; one group received soreness inducing initial workout, the other did not.  After the end of the study, both groups had muscle size and strength compared.  The results?  No noticeable difference between the groups [2].

With that in mind, there are some studies which indicate muscle soreness may hasten the process of muscular development. Additionally, for highly conditioned individuals, muscle soreness may become more important.

With all of that in mind, the correlation between muscle damage/soreness and muscle growth, even in highly conditioned individuals, doesn’t follow a linear line.  More soreness does NOT equal more growth.  There is likely a sweet spot where individuals will realize their optimum growth potential, despite any additional worsening of damage/soreness.

Along that line, it can’t be concluded that more soreness will equal more growth.  Just because one workout caused very little soreness while another made walking near impossible, there are no justifiable conclusions that can be made about the muscular progress you’ve made.


The Bottom Line on Muscle Soreness

Muscle soreness is NOT an ideal indicator for muscle growth.  There is quite a bit of variation among individuals, and the amount of soreness felt can very well be related to a specific individual’s genetic makeup than the intensity of their workout.

Not only that, studies are showing that training a sore muscle will NOT inhibit muscle growth or delay recovery [3].  Researchers examined various groups experiencing sore muscles.  One group worked out the sore muscle three days after the initial workout, while the other group continued to rest until soreness subsided.  This protocol was followed consecutively over a period of week.  At the end of the study, there was size or strength differences between the groups.

The big take away here for the average reader at home, should be this:

Don’t feel discouraged or that you haven’t made progress if that muscle soreness you initially felt becomes more elusive.  Muscle soreness should not be considered an indicator of muscle growth.  Muscle soreness may indicate you’re hitting your body in a new or more taxing way, which is a good thing, but don’t let the pain that you feel dictate your opinions on how much progress you’re making.



[1]: 1. Armstrong RB. (1984). Mechanisms of exercise-induced delayed onset muscular soreness: a brief review. Medicine and Science in Sports and Exercise

[2]: Basbaum AI, Bautista DM, Scherrer G, Julius D. (2009). Cellular and molecular mechanisms of pain. Cell

[3]: Chen TC, Nosaka K. (2006). Responses of elbow flexors to two strenuous eccentric exercise bouts separated by three days. Journal of Strength and Conditioning Research