So, even if we agreed that conventional body composition testing methods (BMI, skin folding, electronic impedance, and underwater weighing) are accurate, consistent, and valid (which we know they’re not) here’s the question. What do they tell you about the person that’s being tested?
More specifically, why is it that (under normal, non swimming conditions) a person with 20% body fat is better off than a person with 30% or 40% body fat? The simple answer of course is that the person with 20% body fat is carrying significantly less excess weight around 24/7 than their 30 or the 40 percent counterparts.
And as your excess weight increases, your ability to perform functional tasks like walking up and down a flight of stairs, or getting in and out of an easy chair decreases. In athletic terms, as excess weight increases, your ability to run, jump, climb, and move quickly from side to side decreases. In short, increases in body fat reduce functional performance automatically. Conversely, decreases in body fat improve functional performance, AUTOMATICALLY!!
Moreover, the higher your percentage of body fat, the more wear and tear you place on your ankles, knees, hips, and your heart. The higher your percentage of body fat, the more energy it takes to perform the same amount of physical work
Aeronautical or Automotive Engineers
In aeronautical or automotive terms, engineers design planes and cars around a concept celled “power to weight ratio.” In general the idea is to increase horsepower without increasing the weight. Or you could decrease the weight and maintain the same horsepower. And in the best of both worlds, you would increase the horsepower and decrease the weight simultaneously. All three scenarios increase the vehicle’s power to weight ratio and its performance.
For example, if you can throw 1000 pounds of luggage out of the car’s trunk or the planes baggage compartment, the vehicle will operate under less stress, its parts will last longer, it will fly higher and faster on the same amount of fuel because its physical efficiency has been increased by eliminating the excess weight. The human animal is no different than the car or plane in this regard. Physical efficiency is always a good thing.
Back to the Original Question
Now, let’s go back to the original question. If improved body composition results in improved physical performance, wouldn’t it logically follow that an improved physical performance automatically results in an improved body composition reading? Would anyone argue with the claim that they’re flip sides of the same coin?
If all this is true, then the question becomes, why does anyone ever concern themselves with the BMI formula, skin calipers, electronic impedance gizmos, or underwater weighing when all you have to do is look directly at functional performance in order to know precisely what you really wanted to know in the first place?
A change in pull up performance for example will tell you immediately whether your body composition is improving or deteriorating. A change in your ability to climb a rope, perform hand stand push ups, or dips will tell you immediately whether your body composition is improving or deteriorating.
That being the case, who needs BMI, Skin Calipers, Electronic Impedance Gizmos, or Underwater Weighing techniques? They’re either inaccurate, inconsistent, logistically full of holes, or prohibitively expensive. Lets’ measure function by looking directly at function so we can forget about all the mechanical distractions in between.