Cycling Biomechanics

The biomechanics of safe and effective cycling performance at all ability levels

A key objective of sports biomechanics is to improve performance while reducing the incidence of injury, and knowledge of the biomechanics of cycling can benefit recreational, competitive and rehabilitating cyclists alike.

The study of cycling biomechanics has provided some understanding of how the body applies power to the bicycle and the way external forces are combined in opposition to the cyclist. Some understanding of these mechanisms allows recreational cyclists to position themselves for optimal comfort and efficiency and competitive cyclists to improve their performance in competition. It also helps people undergoing physical therapy to derive maximum benefits from the use of stationary ergometers, and reassures therapists that the demands placed on their patients will improve their condition rather than inducing further trauma.

Power output is important for both recreational and competitive cyclists, since the varying power needed to move the bicycle under different environmental conditions is something every cyclist must contend with, regardless of experience. The ability to apply pedalling forces effectively in training and competition is a major concern, while correct positioning is critical for successful performance and injury prevention. This article considers some variables associated with rider position and equipment set-up.

Saddle height

Alteration of the saddle height changes joint angles and muscle lengths, thereby changing the kinematics of cycling and the force output of muscles. In a number of studies relating power output to saddle height adjustments, the optimal saddle height, using a seated upright position, has been reported to be 109% of leg length(1,2) (figure 1). This height is considered most efficient for tasks requiring anaerobic work of high intensity for short durations, and approximately 1% less power is delivered for every 1% that the saddle height deviates – in either direction – from 109% of leg length. This is obviously of particular importance to track sprint cyclists, who are required to produce extremely high power outputs for very short periods.

Studies looking into the effects of saddle height adjustments on oxygen consumption and lower limb kinematics have shown that, under steady state conditions against a moderate workload, a saddle height of between 105% and 107% of leg length requires the lowest oxygen consumption(3,4). Lower oxygen consumption for the same power output denotes increased efficiency, which is of particular importance to both touring cyclists and endurance stage racers, who have to ride for long periods.

Figure1: methods used to measure leg length, saddle height and crank length

From The Physiology and Biomechanics of Cycling (1)

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