From bipedalism to bicyclism: evolution in energetics and biomechanics of historic bicycles

We measured the metabolic coast (C) and mechanical work of riding historic bicycles at different speeds: these bicycles included the Hobby Horse (1820 s), the Boneshaker (1860s), the High Wheeler (1870s), the Rover (1880s), th e Safety (1890s) and a modern bicycle (1980s) as a mean of comparison. The rolling resistance and air resistance of each vehicle were assessed. The me chanical internal work (W-INT) was measured from three-dimensional motion a nalysis of the Hobby Horse and modern bicycle moving on a treadmill at diff erent speeds. The equation obtained from the modern bicycle data was applie d to the other vehicles. We found the following results. (i) Apart from the Rover, which was introduced for safety reasons, every newly invented bicyc le improved metabolic economy iii) The rolling resistance decreased with su bsequent designs while the frontal area and, hence, aerodynamic drag was fa irly constant (except for the High Wheeler). (iii) The saddle-assisted body weight relief (which was inaugurated by the Hobby Horse! was responsible f or most of the reduction in metabolic cost compared with walking or running . Further reductions in C were due to decreases in stride/pedalling frequen cy and, hence, W-INT. at the same speeds, (iv) The introduction of gear rat ios allowed the use of pedalling frequencies that optimize the power/contra ction velocity properties of the propulsive muscles. As a consequence, net mechanical efficiency (the ratio between the total mechanical work and C) w as almost constant (0.273 +/-0.015 s.d.) for all bicycle designs, despite t he increase in cruising speed. In the period from 1820 to 1890, improved de sign of bicycles increased the metabolically equivalent speed by threefold compared with walking at an average pace of ca. + 0.5 m s(-1). The speed ga in was the result of concurrent technological advancements in wheeled, huma n-powered vehicles and of 'smart' adaptation of the same actuator (the musc le) to different operational conditions.