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February 29, 2012
The Best Body Fat Measurement
Only recently, has our culture turned to body fat measurements to gauge athletes, ranging from skin fold calipers that measure fat under the skin to bioelectrical impedance that measures the flow of electric current through the body. However, while helpful for the general population, these values are perhaps the most deceiving factor for athletes. Like our evolutionary ancestors who only worried about survival, athletes are only worried about their performance results, which are not necessarily linked to a better looking midsection. In fact, as reported by the Wall Street Journal, there is a disconnect between athletic success and body fat percentage. This past professional baseball off-season saw the signing CC Sabathia, Albert Pujols and Prince Fielder to a committed $590 million to 825 pounds of ballplayer.   A more scientific approach involved a 2011 study of the University of Kansas looking at collegiate baseball players and the best correlations to the most important component of their performance, batted ball velocity. The authors examined several upper body strength variables, ground reaction force, and individual anthropometric variables, such as body weight and height. Not surprising, upper body values, like grip strength, were not even in the top 5 because most athletic movement starts from the ground up. So the force generated by the legs and torso are most significant, not tension created by the upper body (see Sparta Point). Among the top 3 values in the study were peak front force, height, and body weight. The biggest correlate, peak front force, makes sense, as this physical attribute allows you to stop rotation by pressing down into the ground. This variable has proven time and time again to be the best determinant for rotational power (see Sparta Point). Since we cannot change your body height, the only remaining major factor we can improve is body mass. Not body composition, but body mass! Prince Fielder can tell you that getting his entire weight behind the ball will has allowed him to increase batted ball velocity, or rotational power. Does that mean you should pursue greater body mass at all costs? Certainly not, especially since the #4 correlation in the study was squat strength. That body mass has to be functional, meaning the more muscle you have, the more force can be generated into the ground allowing you to develop more power. The best measure of this strength is called relative strength, the maximum force you can develop per pound of your body weight (see Sparta Point)
Body Weight helps you PUSH (GRF)
But since the ideal body weight for your best relative strength is different for everyone, the best test is ground reaction force (GRF). This perfect body fat assessment analyzes your body weight plus the additional force you can develop by pushing into the ground through the energy developed by your muscles. Fat cannot develop tension or force, but as your body fat drops, you do run the risk of losing muscle, primarily as a protective effect by your body. So for you soccer or basketball players that cannot look like Prince Fielder, do not worry, because the nature of your sport that involves large volumes of running and jumping, will raise your metabolic rate high enough to prevent excessive fat gain. So stay focused on your physical performance, best gauged by GRF, and the specific skills of your sport. When your batting average or shooting percentage starts to include body fat percentage, we will advise you differently.
February 29, 2012
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5 thoughts on “The Best Body Fat Measurement”

  1. Babe Ruth could have increased his relative strength by losing some fat. Given how fat he was, with an appropriate diet, it would have been relatively easy to lose 20 lbs of fat and keep nearly all his muscle. His relative strength would go up, but I feel like the momentum he could apply to a ball would go down. I think he would have been a less powerful hitter. If he were jumping, fat would be bad, but since in batting you apply force horizontally to gravitational forces, gravity’s impact is negligible. Intuitively, I feel like, then, that the extra fat mass helps him end up with better numbers in the momentum equation. Thoughts?

  2. Or, perhaps being fat helps by allowing the bat to be stiffer at ball contact, so it imparts more force on the ball. Like, if I push a little kid he’ll fly back, but if I push a sumo wrestler he won’t move. That’s not due to strength, primarily, mostly just mass inertia. I think similarly, a smaller man will dissipate more of the contact forces than a larger man, just for being smaller. I’m no physicist though.

  3. A great weightlifting coach once said “Mass moves mass,” no doubt the body weight helps, however, these are STRONG individuals. As far as momentum, fat is only along for the ride, initially it takes muscle to generate force and break inertia to generate momentum; the more weight, the more muscle it takes to move it. That’s why GRF is still the best gauge, because it takes into account bodyweight and the strength the individual possesses to accelerate it. High GRF means you are sufficiently strong for your bodyweight, regardless of how fat you are, low GRF you aren’t strong enough, no matter how ripped you look.

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