It's when your body feels comfortable after one mile or one hundred miles. Once you find the magic seat, handlebars and pedal position, you can put all your muscle behind going fast.
But in triathlon, bike fit's not that simple, since you've got to make yourself as aerodynamic as possible. While it may seem easy enough to accomplish -- throw an adjustable pair of aerobars on your road bike and go -- it's not. The big reason? Pretty much every stock bike on the market is designed for a man, and the arms forward time-trial position needed for a triathlete only exacerbates the differences between a male and a female -- and not in a woman's favor.
Where a man might comfortably fit on most bikes, a woman on the same ride would be strung out like Supergirl. This is because the top tube of the bike, the tube that runs between the seat and the handlebars, is made for an average man's longer torso and longer arms. Not only does a woman endure more pain in her back and shoulders from this hyper-extended position, she also can't generate as much power as she could if her torso was in a more compact position.
For this reason, women should seek out a women's specific bike frame such as those manufactured by Specialized whenever possible. These bikes feature shorter top tubes that make it easier to reach the bars.
If you're a woman who's too tall to fit on a women's frame -- most bikes designed for females are much smaller than bikes sized for the average male -- ask your local bike shop which bike manufacturers use shorter top tubes in their bike lines. Even within the men's category, there are frames that are longer than others, and if you pick a brand that likes to use shorter top tubes, you might find a nice fit.
When it comes to using a men's frame, do your arms and shoulders a favor and bolt on a highly adjustable set of aerobars. You want to find a pair that can be shortened enough so that when you drop into your aero position with your hands forward and your back flat, the upper arms and torso make a 90-degree angle.
This angle provides the most comfortable support for the upper body in the aero position. And don't think that just because you purchased a tri-bike, fully rigged with aerobars, that you don't have to worry about fit. True tri-bikes -- again, designed for men -- are even more challenging for women to feel comfortable riding. With one of these race rockets, you may have to throw out the stock bars that came with the bike for one that can adjust to your shorter top half.
Of course, the ultimate and very pricey answer for a woman trying to find comfort on a bike is a customized frame -- built to her exact measurements. For some women, this route may indeed be the only option. A six-foot tall woman may be taller than the average male, but her female proportions mean that she won't fit on even the biggest stock frame.
Once you do find your perfect set of wheels, understand that your body still needs to "learn" the time-trial position. When you're torqued over with your arms on your aerobars, you're tapping new muscles in your back and relying on more of your glutes to motor you along.
Until you build up those muscles to handle the workload, you may not produce any noticeable increases in speed. Given time though -- you'll adapt -- and soon start piling on the miles faster than you ever thought you could
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Ivana Bisaro MS of Colorado Springs, Colorado is a Coach for Carmichael Training Systems. She's a cycling and road cycling specialist with coaching certifications from the U.S. Cycling Federation and the National Strength and Conditioning Association. She's also a NASN certified sports nutritionist.