Feature of the Month
Proper Aero Bike Fit for the Triathlete or Duathlete
As a solo rider, you do not have the benefit of being protected from the wind by a peloton of other riders as you would in a road race. When you are riding on your own, overcoming air resistance uses 65-70% of your energy. An aero position is designed to help you maximize your aerodynamic efficiency by reducing your frontal surface area through a lower torso position. However, aero positions have some risks associated with them, and two of the most common discomforts and injuries riders experience are to the hamstring and erector spinae muscle groups. These injuries are primarily caused by the muscle groups being put into positions that stretch them beyond their capabilities.
Lowering the torso into a more aero position -- without making other changes simultaneously -- is a lot like doing a deep toe touch: the lower you go, the more strain is placed on the erector spinae and hamstrings. And, if you go too far or too fast, you can tear one. In its simplest terms, when strain on a muscle exceeds its capacity to stretch and support, pain is the result and injury may occur. How to address this from a cycling position perspective is a more complicated subject.
There are four main factors that can contribute to strain and discomfort to the lower spinae and hamstrings in an aero position:
1. Saddle height 2. Saddle fore/aft positioning 3. Arm pad height 4. Bike length
1. Regardless of the other potential solutions, riding with the proper saddle height is crucial to comfort and power. A saddle that is too low can prevent the lower spinae from extending fully and thus cramp the muscles, while a saddle that is too high can overextend the muscles and repetitively pull on them. Both can lead to discomfort. Because of the greater pelvic rotation encouraged by a lower torso position, most triathletes should be riding with a saddle height slightly below what they would ride on their road bike. Flexibility and alignment are variables that should be assessed and considered before determining proper saddle height.
2. If you are riding on a more relaxed seat angle road bike (< 76° seat angle), or with your saddle far back on its rails on your triathlon-specific bike, moving the saddle forward can take load off strained hamstrings and lower spinae. As the saddle is moved forward, it relaxes the angle created between the lower back and the leg. This not only takes strain off the lower spinae, but can also reduce pull where the hamstrings attach to the ischial tuberocitis on the pelvis. Moving the saddle on the rails should be done with care as it will also effect the length of the bike and the relation of the knee to the foot while riding. Both of these items can directly affect other aspects of comfort and performance while riding.
3. If you are already riding in a forward seat angle and are experiencing hamstring or lower back pain, you will want to look at the height of your aerobar arm pads. Many athletes, in their quest for speed, are riding bikes with very low arm positions. Regardless of forward seat angles, this can still put a lot of load on the musculature of the lower back and hamstrings. Except in very rare circumstances, the solution is to raise the arm pads until the height places the torso angle within the rider's comfort zone for his or her flexibility and strength.
4. A bike that is set up too short from saddle to handlebar can cause the spine to curve and will load up the lumbar and lower thoracic areas, causing discomfort. For riders in this situation, the length of the bike needs to be extended. Depending upon the situation, this is best accomplished through a saddle adjustment, longer aerobars, or a longer stem.
There is a small segment of riders who simply cannot ride comfortably in an aero position. These people may have severe sciatica or other mitigating factors (like an injury) that limit them. Riding technique can affect comfort and efficiency too, but these are beyond the scope of this article.
The most efficient aero positions possible require excellent flexibility and strength to be held comfortably and without risk of injury. If you want to ride in such a position, it is important that you consistently focus on stretching and strengthening the associated muscle and tendon groups (erector spinae, hamstring, psoas, iliotibial tract, and hip flexor). Many inexperienced riders and riders with poor flexibility should start riding in a more upright and relaxed road-based position, which places less strain on the lower back musculature and hamstrings. ?As they progress and cycling strength and flexibility improve, a program to develop into a more aggressive position can be instituted over time.
Regardless of experience and flexibility, if you want to maximize your power, aerodynamics, and efficiency while riding, it is crucial that your position is built around what your body is capable of holding comfortably. Your position should address your individual needs and physical capabilities. Your flexibility, core strength, body measurements and alignment, riding experience, and any other mitigating factors (injuries, mileage, etc.) must all be assessed before a position is built. Once these variables are established, a qualified technician can combine the information into a dynamic session on a fit cycle where angles can be polished and your body can be balanced. The ideal resulting position will serve to prevent muscle injuries while simultaneously maintaining an efficient and powerful pedal stroke. For strong and experienced athletes, computer-based assessments of aerodynamics, power output and efficiency, and oxygen transfer can also be integrated into an advanced fitting session to further perfect the rider's efficiency.
Like your hair, bike position is dynamic and will change as you age, gain experience, and undergo physical changes. Also like hair, it is a good idea to have it touched up and reviewed periodically by a well-trained specialist. What works now might not be optimal in a year or two, and trying to fix it on your own can often create more problems than it solves.
Ian Buchanan is co-owner of Fit Werx, a triathlon and road cycling specialty company that offers services and cycling products at their offices in Waitsfield, Vermont or mobile services in much of the Northeast. Fit Werx specializes in custom fitting and analysis, products, consultation, and technology research. Ian can be reached at (802)496-7570 or online at www.fitwerx.com.