On the Bike: Fit Versus Technique

<strong>Eneko Llanos stays aero on the Queen K during the 2009 Ironman World Championship.</strong><br><br>Photo: Jesse Hammond/Active.com

Something has been lost in the recent bike-fitting craze. We've forgotten that it's not just about the bike.

The typical fitting is all about setting up the bike to support an assumed position of the rider. The goal is a setup that creates an optimal blend of comfort, power and efficiency, but to actually get this result a fitter must devote just as much attention to the rider's position, which cannot be taken as a given. Unfortunately, few fitters know much about rider positioning.

Worse, many triathletes don't even bother to seek out qualified fitters to work on their positioning. On many triathlon forums, people post side-view photos of their positions and ask board members to critique them. The problem here is twofold. One issue is that air hits you from the front as you cut a hole through it, not from the side.

The second issue is that most of the people replying with positioning advice have never been in a wind tunnel nor are experienced fitters. In other words, they don't know what they're talking about.

Let's look at what wind tunnel testing and real-world experience at the elite level tell us about proper positioning.

Know Your Resistance

There are three major forces that will hold you back when riding your bike on a flat to rolling course: mechanical resistance, rolling resistance and wind resistance.

Mechanical resistance is the least important. It is generated by the gears of your bike, which are fairly efficient, especially on a race-tuned bike, and in the bearings, which are also quite efficient. Rolling resistance is a little more complicated, as it varies by tire construction, inflation pressure and surface smoothness.

Both mechanical and rolling resistance increase in a linear manner, but wind resistance is different because, assuming that there is no change in your body riding position, it increases at the square of the increases in speed. The drag on a cyclist traveling at 20 mph is four times as great as the drag at 10 mph.

Thus, the faster you go, the more power is required to overcome wind resistance. In any given riding position, you need about 33 percent more power to go 10 percent faster. The good news is that you can reduce wind resistance at any given speed by manipulating your position.

The key is to cut down the frontal area of your position, forming your body into a more streamlined shape on your bike. Watch the Tour de France and you can tell which teams and athletes take this streamlined position seriously and which do not. The same goes for the front of most professional non-drafting triathlon fields.

A rule of thumb developed by Steve Hed, of Hed Cycling Products in Shoreview, Minnesota, is that you can save three seconds over 40 kilometers for every 10 grams of drag dropped. There are 454 grams in a pound; therefore, dropping a pound of drag can save you roughly 2.5 minutes over 40 kilometers and more than 11 minutes over an Ironman bike course.

Reducing Drag

The most effective positioning change you can make to reduce drag is to lower your head as much as you can toward your hands. This change alone has been shown reduce drag by more than 200 grams in the wind tunnel.

aero bike position AB
Photo A: Good head position. B: Poor head position.

Taller athletes typically cannot get their head as close to their hands as shorter athletes because of the length of their upper arms.

They can overcome this disadvantage to some degree by angling their forearms upward. When this is done properly, you can actually hear the wind resistance decrease.

The next biggest time savings comes from repositioning your shoulders. The objective here is to narrow your shoulders by rolling them inward. To do this, get into your riding position indoors and look directly into a mirror. See if there is a way to "shrug" your shoulders to be narrower. Modifying your elbow and hand position might make it easier.

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