Modern Bike Fit and the Power Triangle

Guest Blog: Wenzel Coach – John Forbes

Slam that stem down as far as it will go! Look like a bike racer! Get those elbows as close together as possible! You must sacrifice all for aero! Comfort is for the weak!Some of the top bike racing teams in the world still believe those words, but thankfully their numbers are increasingly few.  Many team leaders who used to maintain this litany are now fervent converts to what is becoming accepted fact: comfort and power go hand in hand. You not only do not need such comfort sacrifice but should actually avoid it. Stem to saddle drop, for instance, is dictated by what each person’s body allows. Some of us may benefit from eight centimeters of drop while others work best with two or three.Very few riders gain from slamming their elbows together on TT or Tri aero bars. Not only does it not increase one’s aerodynamics, but far more importantly it severely restricts one’s lung capacity, thus dramatically reducing power. After all, maximal oxygen intake is essential for performance.

Making Power

Bike power comes in two parts; the engine – the saddle/leg interface; and the carburetor or upper body – the lung/cardio system. We’re going to talk engine – specifically the power triangle and base of the engine’s moving parts.

If you think of the saddle as the base for a triangle with the hip joint as one point, the outer interface between the knee and the tibia another and the outer bump on the outer ankle as the one that then connects back to the hip you realize each of us a given number of millimeters in that triangle.  Saddle fore/aft position-setback is determined by a ratio based on femur length compared to tibia length. Here, the longer the femur in that ratio the further back the saddle sits on its rails. But if the saddle is well back, then saddle height is less if we think of the triangle and the given number of millimeters. This is why two people of the same height, even with the same total leg length, won’t necessarily have the same saddle height.

While there are numerous views about proper pedaling technique, there is wide spread acceptance that one must begin with a stable platform. Think of your feet as the base for that platform. As upright beings, one of our strongest stances is one in which the foot is neutral to the leg. That is, keep the foot at roughly 90 degrees to the tibia throughout the entire pedaling circle. If you severely drop your heel as you push through the top of the stroke you essentially abandon the muscles at the front of the leg, the ones capable of producing some of the greatest power. So, saddle too low and heel drop = power loss and usually a curved back and discomfort in the lower back and often painful shoulders, hands and even forearms. Saddle too high and you’ll experience serious discomfort in places you don’t want any, as well as a tendency to point your toes which negates your power.  You want the sit bones on the widest flat part of the saddle-the “sweet spot.” When saddle height and or setback are wrong, you can find yourself either curving your back as your hips seek that spot or frequently sliding back seeking it. A professional bike fitter can help you find that “sweet spot” in a comfortable position.

Cleat position is another critical aspect of power production inside the power-making triangle. If the cleats are too far forward there is a significant tendency to drop your heel with all the negatives mentioned above. Angle of the cleat on the shoe is just as important. If you are not centered in the cleat as you pedal, you can put significant pressure on either the outer or inner aspect of your knee.

A modern bike fit can solve the issues that cause you pain as well as help you get comfortable and powerful!

Coach John Forbes has been competing as a cyclist and triathlete for several decades. His experience also includes over 15 years of professional bike fitting. www.wenzelcoaching.com.
Athlinks Staffhttp://blog.athlinks.com
Posts by the Athlinks Staff are authored by our in-house group of athletes and subject matter experts in the fields of performance sports, nutrition, race organization, and training.

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