Introduction
Today’s article is going to talk about a very popular (slight) misconception in the fitness industry. What kind of relationship does muscle size and strength have? Are they linear? Meaning, when your strength increases does the size of your muscles ALSO increase?
My immediate answer to this is “no”, but I truly have no studies or research to go off of to back this up other than experience with myself and my clients. But even then… Everyone is different. So, I decided to put my degree to use and go through peer-reviewed research articles to come up with a more science-backed answer. Something I’d like to preface before getting into the research is to state that I’ll be using “strength” and “force” interchangeably, because force tends to be a better marker of what we think of when we refer to “strength”, and therefore allows us to differentiate between strength/force and muscle size/hypertrophy more accurately. Especially since there are MANY types of muscle hypertrophy and each one affects your body differently.
The goal of this post is to translate the science behind muscle size and strength into concepts and processes that make sense to the average gym-goer, and also in a way that allows you to put this information to use so you can get to your goals much quicker and easier.
Science Behind Muscle Size
During intense regimes of resistance training, your muscle fibers get damaged. When this happens your body repairs them by activating satellite cells (stem cells that are used for tissue repair) which travel to the site of trauma to fuse with each other and the damaged fibers. This fusion increases muscle hypertrophy (muscle size). Some satellite cells duplicate and form new muscle protein strands (myofibrils) while also repairing the damaged fibers. This leads to myofibrils increasing in thickness and also number, giving the muscle a larger appearance. (Keep in mind this is not evident immediately after a workout; it takes months before you can visually notice the change in muscle size, although muscle protein synthesis (process of producing new muscle protein) increases within 2-4 hours after a workout)(Kwon & Kravitz, 2004).
Something important to understand is that muscle growth can only occur when “the rate of muscle protein synthesis is greater than the rate of muscle protein breakdown” (Kwon & Kravitz, 2004); this means that resistance training and proper protein intake needs to “outweigh” the speed at which your body breaks down muscle protein.
When looking at how to build muscle size the most efficient way possible, a few studies showed that high volume training reigned supreme (Krzysztofik et al., 2019). This means a high number of reps and sets per exercise (somewhere between 3-6 sets and 6-12 reps; this is what was studied, and this is what tends to be more manageable timewise and energywise for most people).
Science Behind Strength (Force)
The main difference between muscle strength/force and muscle size is that when the muscles are getting STRONGER, there is an increase in the ability to recruit more muscle cells (and therefore increase power) in a more simultaneous manner, compared to how the cells take turns firing in untrained muscle. This allows your body to produce more force in a more cohesive and efficient way, allowing you to lift heavier weight. Strength training also decreases inhibitory neural feedback, which stops the muscle from overworking and damaging itself by generating a force it is not yet able to. These types of neural adaptations allow for “significant strength gains with minimal hypertrophy” (minimal gain in muscle size).
Keep in mind that while you’re gaining these neural adaptations there is still likely going to be damage to your muscle fibers, which means while they heal they will get slightly larger (this of course depends on the type of training you do along with other factors that assist in recovery).
When looking at how to gain strength in the most efficient way possible, the same studies showed that groups of individuals doing fewer reps and sets made the most progress. An interesting finding as well was that muscle strength tends to progress faster than muscle size. This could be helpful to keep in mind when beginning a training program, to set realistic expectations and know what to expect.
Relationship Between Muscle Size and Strength/Force
This answer is not going to be very exciting (there’s your warning), it is interesting however! The overall conclusion is that there is still confusion over the relationship between muscle size and muscle strength. But, after looking at studies comparing different training styles it does seem as if there is no linear relationship between muscle size and muscle strength; and if there is any correlation at all, it is “weak” (Reggiani & Schiaffino, 2020). Keep in mind that every individual is different, and that some people may gain size easier than others while others may gain strength easier. Differences in sex play a role as well (mainly with muscle size), meaning that women tend to not get as “large” as men but can get very strong without the added size. A few studies were looked at putting groups of men into different training style categories (high reps/sets, moderate reps/sets, and low reps/sets) and it was found that muscle size was greatly increased for those doing high volume (5 sets/exercise) and moderate volume (3 sets/exercise), but not as much for the group doing low volume (1 set/exercise)(Reggiani & Schiaffino, 2020). The group doing lower reps/sets, however, was found to have a greater increase in strength, but not necessarily size. Overall, there are different processes at play when gaining muscle size compared to gaining muscle strength; gaining size is due to the increase in number and thickness of myofibrils, while gaining strength is due to neurological adaptations and the brain’s ability to recruit motor units more efficiently (this process also plays a role and is referred to as “muscle memory”). Due to these different processes, muscle size and strength don’t seem to relate in a completely linear way (meaning as you get stronger, you don’t necessarily get “bigger”, depending on the type of training format you do), but they do crossover more or less depending on the individual.
My Take on the Research/ Conclusion
Overall, my take on the research is that due to the difference between what happens anatomically and neurologically when gaining either muscle size or strength (and the needed difference in training styles to prioritize one or the other), there is a very slight correlation between muscle size and strength. VERY slight. I would say it is safe to say that you can be strong without having large muscles, and you can have large muscles without being strong. After putting together the research, studies, science, and my own personal experiences, it seems as if strength and size are not linear. But they do blend. It is more gray than black and white. I highly recommend you test this out yourself and keep the research and studies in mind while making your own conclusions and doing your own research. I am just one person, and although my experiences and findings support my original assumption (that strength and size do not have a strong correlation), I may be wrong! I hope this breakdown helps you understand what exactly is happening when your body gains size compared to strength, and I hope this allows you to draw your own conclusions as well!
As always, thank you to those who have made it this far!
Until next time,
-Taylor
References
Krzysztofik, M., Wilk, M., Wojdała, G., & Gołaś, A. (2019, December 4). Maximizing muscle hypertrophy: A systematic review of advanced resistance training techniques and methods. International journal of environmental research and public health. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6950543/
Reggiani, C., & Schiaffino, S. (2020, September 9). Muscle hypertrophy and muscle strength: Dependent or independent variables? A provocative review. European journal of translational myology. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7582410/ Young sub Kwon, M.S. and Len Kravitz, Ph.D. (2004) How do muscles grow? (n.d.).
https://www.unm.edu/~lkravitz/Article%20folder/musclesgrowLK.html