A proper bike fit will make a world of difference in both your riding comfort and speed. From a general viewpoint, you should break your bike fit down into three categories: seat height, handlebar height, and seat fore-aft positioning. Lets first look at seat height. Start by setting your seat at the highest possible level, while still allowing for a smooth spin, which means that your hips shouldnt be rocking from side to side to reach the bottom of the pedal stroke. The toes should not have to point excessively to reach a full extension in the pedal stroke. The best way to get the seat height correct is to sit on the seat and extend your leg as far down as the crank allows (make sure youre clicked in if wearing bike cleats). Fully extend the leg by locking the knee back. Make sure your foot is parallel to the ground. If your toes have to point down with the leg fully extended, then your seat is too high. If your heel has to point down with leg full extended, your seat is too low. Of course, when actually pedaling, your toes *will* be slightly extended, but your knee will also be slightly bent, not locked out like it is when you are testing your bike in a stationary position. Remember, while a seat that is too high will simply affect your ability to produce optimal power, a seat that is too low will put excessive force upon and eventually injure the knee joint. Moving on to handlebar height: a general recommendation is 1-3 inches below the height of the saddle. Of course, this value will vary as a function of back flexibility. You should be able to maintain softness or a slight bend in the elbows, without feeling too much pressure on the palms of your hand. Of all bike measurements, handlebar height is the most subjective it really does depend how much bend you can maintain in your low back joint while staying comfortable throughout the ride. As flexibility improves during your training, you should be able to gradually lower handlebar height, ideally in small increments. If using aerobars, follow these 3 recommendations: 1) your forearms should be level when viewed from the side, with your ears above your elbows; 2) the elbow angle should be 90-110 degrees. Over 110 is too large an angle that can cause back problems, and under 90 degrees is not aerodynamic enough; 3) the width of the elbows depends on your flexibility. There is no perfect measurement just like handlebar height, you should experiment with various angles until you find the most comfortable position that offers the greatest speed. Finally, the seat fore-aft position is another important measurement. Basically, with the crank at 90 degrees, a straight line from the front of the knee should drop into center of the pedal axle. Your seat tube angle is the adjustment that will affect fore-aft position. Ranges fall from 72 to 78 degrees, with triathletes usually riding at a higher angle. The higher the angle, the more the hamstrings are involved in the pedal stroke, and the easier a high cadence becomes. A greater amount of hamstring involvement will leave your hamstrings warm and your quadriceps fresh for the run. However, the an excessively steep seat tube angle can cause speed decreases due to less assistance from the more powerful quadriceps group, and from gravity, which can offset the gains of using the hamstrings. Furthermore, it becomes less biomechanically efficient as the seat position moves farther forward to push over the top of the pedal stroke, due to an excessive lower leg angle relative to the crank arm. You should take your bike out and test both speed and comfort level at varying seat tube angles. Remember, if you have low back pain or tightness, a more forward seat position can be more comfortable. However, if you find that you continously deal with a tight low back on the bike, try bringing your seat position more forward, as it opens the angle between your torso and thigh, thus reducing stress on the low back. As you may have sensed from this article, the best way to determine your optimum bicycle fit is to hit the road and put the miles on your bike. Especially early in the season, constantly analyze how your body feels your back, your hands, your neck, your knees while at the same time glancing at your cyclecomputer to see how changes in your bike set-up affect your speed and wattage. Another good strategy is to use an indoor spinner with your racing bike, so that you can constantly mount and dismount your bike as you make small changes in the set-up. When I train athletes online, I like them to send me a picture of their setup on the trainer, so I can suggest changes. Check out web-based training options at www.pacificfit.net. |
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