The 4-Hour Body_ An Uncommon Guide to Ra - Timothy Ferriss [23]
Because it highlights muscular imbalances between the left and right sides. In my case:
Left arm—4.6 kg
Right arm—4.7 kg (I’m right-handed, so not surprising)
Left leg—12.4 kg
Right leg—12.8 kg
Left trunk—18.9 kg
Right trunk—17.9 kg
As we’ll see in “Pre-hab,” making yourself injury-proof requires, above all, correcting left-right imbalances. In five to ten minutes, DEXA gives a crystal-clear picture of mass imbalances that even outstanding physical therapists can miss after hours of observation.
BODPOD
Costing just $25–50, BodPod uses air displacement and is comparable to the clinical “gold standard” of hydrostatic underwater weighing. The subject (you) sits inside a sealed capsule, and alternating air pressures determine body composition. Infinitely faster and more comfortable than underwater weighing, the BodPod is the official bodyfat measurement device of the NFL Combine, where the 330 best college football players are analyzed by NFL coaches and scouts to determine their worth.
Unlike calipers and some other methods, BodPod can accommodate obese subjects of 500+ pounds.
BODYMETRIX
BodyMetrix is a hand-held ultrasound device that tells you the exact thickness of fat (in millimeters) wherever you place it. It ended up being the tool I used most often and still use most often.
Ultrasound has been used for more than a decade to determine the fat and muscular characteristics of livestock. Want to see how that intramuscular marbling is coming along on your living Kobe beef? Pull out the pregnancy cam!
It’s amazing that it took so long to reach athletics. The next-generation BodyMetrix wand, small enough to fit in a jacket pocket, connects to any PC with a USB cable and is now used by world-famous teams like the New York Yankees and AC Milan football. It is the picture of simplicity: I was able to take frequent readings in less than two minutes, and both data and images were automatically uploaded to my Mac. (The PC software actually runs faster on a Mac using Parallels®, a program that allows you to use PC software on Macs.)
Rather than attempt to find a gym that offered this for per-session fees, I decided to own a unit. At $2,000 for the professional unit, it was worth the convenience. There is a personal version in development that will cost less than $500.
Can’t Find the Fancy Stuff?
If you choose to use calipers or bio-impedance (any tool you hold or stand on) out of convenience, or if you use them for more frequent measurement alongside one of the Top Three, here are critical points to consider:
1. NEVER COMPARE BEFORE-AND-AFTER RESULTS FROM DIFFERENT TOOLS.7
Results from different tools cannot be compared. In my 24-hour measurement marathon, I tested 13.3% with BodPod and 11.3% with DEXA. Let’s say I had tested using only DEXA at 11.3% and then tested on BodPod for my follow-up, which resulted in 12.3%. I would wrongly conclude that I’d gained 1% bodyfat, whereas I would have seen a more accurate 1% loss had I used BodPod for both.
2. IF YOU CHOOSE TO USE BIO-ELECTRICAL IMPEDANCE (BEI),8 YOU NEED CONSISTENT HYDRATION.
Using bio-impedance devices, I have been able to make my bodyfat percentage jump almost 1% in five minutes by drinking two liters of water in between measurements. Here’s a simple approach that largely fixes hydration issues:
Immediately upon waking, drink 1.5 liters (about 50 fluid ounces) of cold water9—ensure that water temperature is the same day to day—and wait 30 minutes. Urinate and then test bodyfat using bio-impedance. Do not eat or drink anything else before testing. I use two empty Bulleit bourbon bottles (750 milliliters × 2 = 1.5 liters) because I love the old-school bottles, but Nalgene bottles are generally one liter each and have line measurements on the side. Wine and most liquor is also standardized for a 750-milliliter bottle size.
3. IF YOU CHOOSE TO USE CALIPERS, YOU NEED A CONSISTENT ALGORITHM.
Even with the same calipers, using different math = different results. I suggest asking