Bike Fit and Pain While Aero

author : AMSSM

comments : 0

Is it normal to have pain when switching to a tri bike?

Question from Member TMS:

I recently bought a used triathlon bike, my first. I used the Fast Bike Fit App this weekend to try to get in the ballpark with a basic position profile. Here's the video of my first trial.
https://www.youtube.com/watch?v=QcithKZbmgs

Based on feedback I got from a couple locations, I lowered the seat about one cm from where it was in the above video.

I tried to do my first actual workout on the bike this morning and am having a problem with shoulder pain in the aero position. Specifically at the front of my shoulders, in the area of the long biceps tendon. The aero bars were in the most inward position to start, but the pads were at the widest position relative to the aero bars. It hurt right away. I moved the aero bars out ~ 2cm each, only got a little relief. Moved them out as far as they'd go (about another ~2 cm each), and it helped a little, but not much. I started uncomfortable, but within 5 minutes discomfort grew to pain again. I really couldn't hold aero position for much more than that. Tried different vertical angles for the aerobars, but it made no appreciable difference. I was very conscious not to be gripping the bars. I had my hands in a relaxed position over the ends, and minimal tension in my forearms (unlike in the original video).

So, is this a common issue for someone new to a triathlon/TT bike? Do I just need to get acclimated to the position? Are there stretches I should be doing? Or is it possible I'm just too broad shouldered for the range of position available with this base bar/aerobar position? FWIW, I come from a competitive swimming background and, while not extreme, do have the prototypical "broad shouldered swimmer's physique"....well, except for the 6 pack which hasn't been seen in a number of years.

Answer by Troy M. Smurawa, MD
Member AMSSM

The most important part of fitting is a bicycle is achieving a correct fore-aft position of the saddle. A typical bike has the saddle behind the bottom bracket crank center.  This maximizes power output from the hips and legs. The fore-aft position determines how your body is balanced on the bicycle. The correct weight distribution is 60% on the saddle and 40% on the handlebars. The angle of the frame tube partly determines the fore-aft position of the saddle relative to the bottom bracket crank center and pedals.  As you move to a more aerodynamic horizontal position, the saddle is positioned further to the rear to maintain good body balance.   The triathlon bike frame is built with a steeper seat tube angle, which positions the saddle further forward while maintaining the correct saddle to crank position. This allows the rider to optimize power output from the hips and knees onto the cranks while achieving a more aerodynamic position.

Next, the handlebars are positioned so that the cyclist is able to maintain good posture, a good hip-torso angle, and not over-reaching. When using aerobars, the elbows should be directly below the shoulders and bent at 90 degrees. The elbows should be flat and horizontal to the ground, the elbows are inside the hips when looking from the front, and the shoulder are 1-2 cm behind the elbows. Too long of a reach will put stress on the back and shoulders and cause the rider to slide forward on the saddle. The height of the handlebars depends upon saddle setback, the type of bike (road vs. triathlon vs. mountain), cycling distance, flexibility of the hamstrings and lower back and individual morphology (torso, leg and arm length). The further back the setback, the higher the handlebars need to be raised to achieve good hip range of motion. The better the hip and back flexibility the lower a rider can effectively lower the handlebars. Good flexibility will allow a rider in the aerodynamic position to achieve a flat torso rather than a flat back. Lack of flexibility and improper shoulder and arm position will lead to a more forward weight distribution and more stress on the shoulders. Cyclist riding shorter distances can tolerate a lower more aerodynamic position whereas cyclist riding longer distances may need a higher more comfortable position. Triathlon bikes require a lower more aerodynamic position whereas mountain and recreational bikes with a higher position will have better stability and control of the bike.

Lastly, a bike fit app or a professional bike fit helps a rider find the most aerodynamic position, but a rider’s physical body type, flexibility and body proportions are important factors that will determine the best aerodynamic position on a triathlon bike. A rider needs to feel relaxed, comfortable and have the capacity to maintain the aerodynamic position while riding in order to benefit from that position. Obtaining an efficient, aerodynamic and comfortable fit on a triathlon bike often takes multiple adjustments and time to acclimate to that position.

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date: June 23, 2017