I bet everyone who spent at least a month in a gym asked themselves this question. We start working out either to lose weight, which is not the best weight loss strategy, or to become more muscular, or both. And as long as we set the goal of building muscle, we ask ourselves this question - how will I look in a while? How much more muscular will I become?
I've spent a good amount of time trying to find the answer to this question and, unfortunately, all the blogs and YouTube videos I found had the same structure - first, someone talks at length about individual variability and ends up saying that the answer is "it depends" and I always felt like I wanted my 15 minutes of life back - I just need a number that I can use for my purposes, that's it. So today I'm going to give you this number, actually, even better - I'll give you the formula you can use and the tool to make calculations easier. A disclaimer - at this point I can only talk about adult men, but I hope to come up with something similar for women too.
So, how do we calculate the amount of muscle we can build in three easy steps?
Step 1: Calculate your lean body mass.
I think, it's only logical to start with understanding your current body composition. It's quite difficult to calculate you muscle mass - you have to use quite sophisticated tools for that, ideally a DEXA scan, but for our purposes the lean body mass (LBM) will serve as a good starting point as it changes pretty much only due to increase or decrease of muscle mass - most of our organs like the brain or the liver do not change much throughout life and even hydration levels affect mostly muscle mass. So, in brief, when you train both your muscle mass and you LBM change and the changes in LBM approximate the change in muscle mass.
Δ LBM ≈ Δ Muscle Mass
Accordingly, we can use the change in LBM as the measure of muscle mass change.
Calculations: Measure your body weight (BW) and you body fat percentage (BF%) and use the following formula to calculate your LBM:
LBM = BW x (1- BF%)
I have a whole blog dedicated to measuring these, feel free to check it out here or you can use the Toolbox on my website to calculate them.
Step 2: Calculate your "potential" LBM.
This step is a bit tricky - we are not talking about your genetic potential here, but rather an estimate of what you can become after a decent amount of training. In order to estimate it, I will use the data from the study of Kouri et al., 19981 - they did a research study on fat-free mass index (FFMI) in individuals who used steroids and those who didn't. For obvious reasons we will use the data for those who didn't use steroids. These subjects (n=74) were training for at least 2 years and, I may assume that they are a good representation of an average guy who works out with moderate degree of dedication and achieves decent results over the course of 2+ years of systematic training. The average result that they got is a nice approximation of what you can achieve, but by all means your genetic potential is way higher and if you work out better (better training program, perfect nutrition etc.), likely, you can get better results. In any case, I think that the average FFMI of 21.8 is a fair estimate of what can be achieved and what can be set as a goal for the first year or two of training.
Calculations: FFMI is calculated as your LBM divided by your height in meters squared. Accordingly, you potential LBM is:
Potential LBM = 21.8 x (Height in meters)2
NB: If you struggle with conversion units, you can use the converters on my website.
And now, when we have both your current and potential LBM, we can move to the last step.
Step 3: Calculate the difference
This step is the most straightforward one - all you have to do is just calculate the difference between the current and the potential LBM as it approximates the change in muscle mass:
Calculations:
Δ Muscle Mass = Potential LBM - Current LBM
Bonus point: The range
For those of you who are scientifically inclined or interested in more sophisticated answer - we can actually calculate the range of potential LBM and, accordingly, the range of your muscle building potential. All we have to do is to use the standard deviation from the study of Kouri et al1 to calculate the 95% confidence interval for the value in question. I don't want to overcomplicate things for you, so I won't talk much about the math behind that calculation. In the end of the day, we do have the tool that you can use for hassle-free calculations here.
As always, I hope that you find this information useful and encourage you to subscribe to both this website and to my YouTube channel so you won't miss anything. Feel free to ask questions, make comments - I'm always happy to answer them.
Sincerely Yours,
Dr.Sam
Video: How much muscle can we build? The Scientific Answer: Dr.Sam's Formula