How to Measure Muscle Mass

Some weightlifters like to know what percentage of their total weight is muscle and the lbs / kgs of muscle they have. There are several different methods for measuring or calculating the amount of muscle mass in the human body... And the methods are all highly inaccurate.

The only way to directly measure muscle mass is via cadaver dissection, which is not a good option! The methods described below are estimations, and based on different assumptions, and with varying degrees of accuracy. You've been warned!

The human body is made of several things:

Muscle Mass
Fat Mass
Bone Mass
Blood Mass
Waste Mass (Urine, Excrement)
Organ Mass

And so forth. Usually what people want to know is how to measure their Fat Mass and their Muscle Mass, often represented as a percentage of their total weight. Body Fat % X Total Body Weight = Fat Mass; Muscle % X Total Body Weight = Muscle Mass.

There are machines (electronic gadgets) at gyms that can give a rough estimate of fat mass and then using your weight it can be used to calculate the approx. muscle mass. But its based on a percentage and makes a number of assumptions that, including that the fat estimate was accurate and ignores things like above/below average bone and organ weight.

GIRTH MEASUREMENTS

Girth measurements can be used to monitor changes in muscle mass. As the girth measure will also include the fat underlying the skin, any changes in your body fat will affect the results. Therefore, girth measures themselves are only a rough guide to muscle mass changes. The calculation below adjusts the girth measures based on skinfold levels in the calculation of muscle mass.

The Girth Muscle Mass Calculation equation to use is as follows, where: H = height, FG = forearm girth, CG = calf girth, CCG = corrected calf girth, TG = mid-thigh girth, CTG = corrected mid-thigh girth.

CTG = TG - π(mid-thigh skinfold/10)
CCG = CG - π(calf skinfold/10)
Muscle mass (g) = H(0.0553CTG² + 0.0987FG² + 0.0331CCG²) - 2445

24-HOUR URINE CREATININE MEASUREMENTS

Another method for determining muscle mass is through the measurement of the 24-hour urinary excretion of a chemical called creatinine. This method is based on on the correlation between total body creatine and urinary excretion of creatinine, and assumes that nearly all creatine is within muscle tissue, that muscle creatine content remains constant and that creatinine is excreted at a uniform rate.

BODY SCAN

The following methods are not used routinely to measure muscle mass, though it is possible to get estimates of muscle mass from these measurements. Most of these methods require sophisticated and expensive equipment, not usually available for most people.

Dual-Energy X-Ray Absorptiometry (DEXA) - using this method you can determine body components including non fat soft tissue.
Total Body Potassium (TBK) accurately determines the body's total cell mass (that is, the active growing tissues in the body), which in turn can be used to estimate fat-free or lean body mass. When this measurement is combined with measurements from the Total Body Protein, you can determine total organ and muscle mass.
Magnetic Resonance Imaging (MRI) - with MRI it is possible to get accurate measurements of the composition of body tissue, by identifying muscle, fat and organs etc.
Total Body Electrical Conductivity (TOBEC) - can be used to estimate lean body mass.
Computed Tomography (CT) - the high quality images can be processed to differentiate and measure the amounts of fat and lean body tissue.

WHAT'S THE POINT???

So yes, you can try to measure your total muscle mass. But do you really need a number? What difference will that number make beyond bragging rights?

If you're going to do any kind of measuring the things I recommend measuring is your Personal Best.

How you do that depends on you, but what I like to do when weightlifting is to once a week see what the maximum amount of weight I can lift with a specific group of muscles. And to me it doesn't count as successful unless I can do 10 repetitions of that weight. If I can only do somewhere between 1 and 9 then it doesn't count. If I am going to lift something I don't want to lift it for a few seconds and then drop it and be unable to lift it again because my muscles are too tired. I want to be able to lift it and sustain that weight for a reasonable amount of time.

Once I know I can do that I can say that is my Personal Best and then aim to improve upon that.

Knowing my Muscle Mass percentage is comparatively useless.