A lower riding position doesn’t always bring better results for biking time trialists. Here are gains and losses that an aero riding position brings about.
According to new research carried out at the University of Birmingham, extreme aero riding positions can considerably reduce drag, but they can also affect power output, oxygen uptake, cadence and heart rate. The research examined the performance benefits of different riding positions and discovered a significant trade-off between aerodynamic gains and physiological losses.
While decreasing the angle of the biker’s torso to the ground from 24 degrees to a horizontal zero degrees achieved a 14% reduction in frontal area, which brings a major gain in aerodynamics, this also involved a 14% decline in mean peak power output, down from 369 watts to 319 watts.
At a zero-degree torso angle, the VO2 max, heart rate, cadence and minute ventilation were significantly lowered in comparison with all other positions. When the torso is horizontal to the ground, hip and leg muscles work at a different and less ideal length in terms of producing optimal force for pedalling. What is more, lower torso angles compress the abdominal area, impeding the work of the diaphragm and limiting lung volume.
This research builds on an earlier study, which proved that the optimal torso angle depends strongly on the biking speed, with reducing torso angles at increasing speeds. So for time triallists capable of riding at speeds above 46kmh, the aerodynamic gains of a more horizontal riding position outweigh the losses in power (although a fully horizontal aero riding position is still not optimal). But for speeds below 30kmh, it’s helpful to ride in a more upright time trial position.