Why a perfect fit is crucial
The Importance of Riding a Bike That Fits
All of us have bought a bicycle that does not fit properly. Why? Because all "off the shelf bicycles" were designed with a Pro-rider in mind. For those of you privileged enough to have attended a World class cycle event (Tour de France, Giro d' Italia) would know, that the Pros who race there, do not have the phasic/ biometrics of an average cyclist. Nairo Quintana weights a total of 58kg is a mere 1,67m tall and spends most of his time riding. The point is... the bicycle you are currently riding (assuming it's not custom made) was in fact “designed for him” and proportionally enlarged so you can ride it.
With the above said, an incorrect frame size (designed for a pro-cyclist) can be manipulated to create the impression that it fits, but there will be consequences, such as compromised handling or sub-optimal muscle recruitment patterns, reduced watts or reoccurring injury. A good example of this would be a frame that is too large but manipulated to fit a rider. The first step, shortening of the stem and moving the saddle further forward. The consequence... under-steer and the possibility of losing control of the front wheel during a wipeout in wet conditions. Additionally, an over recruitment of the quadriceps will increase premature fatigue.
Since no two people are the same no two bicycles or setups should be the same. Allow me to tell you a story to emphasise my point. Two brothers, twins, one a professional cyclist the other a weekend warrior. The professional brother spends most of his time riding while his brother rides the Cape Cycle Challenge every year. Even though they have the same phasic their seat height, saddle setback, reach and handlebar drop will not be the same, because of the difference in body conditioning, flexibility and riding style. The professional will be more efficient, producing power, with a more aggressive fitment.
The athlete should not adapt to fit the equipment, rather the equipment should be built for the athlete. The solution to the above problem will be to have a bicycle frame designed for you on paper that incorporates your fitness level, training history, flexibility, and biometrics such as limb lengths, riding style and bicycle application.
The advantages of riding a bicycle that not only fits you but was designed for you are endless. The rider has more comfort, power, less injury and less physical depletion during long rides.