Aerodynamic drag on the bike is strongly influenced by torso angle – lowering your chest towards the handlebars reduces drag, helping you to ride faster.
But go too far and power production in the thighs and buttocks becomes less efficient. So when do losses in power outweigh the aero advantages of lowering your torso? And how is this affected by your speed?
Scientists have used computer modelling to examine this question, collecting data from 19 time-trial cyclists sitting at four different torso angle positions – 0° (horizontal), 8°, 16° and the more upright 24°.
The results showed that once speeds exceeded 28.5mph the reduction in aerodynamic drag outweighed the power losses, meaning that it’s better to get down low, even if that does make it more difficult to produce power. However, a completely horizontal torso wasn’t the best – an 8° angle produced even lower drag.
Conversely, for speeds below 18.5mph, a more upright position nearer to 24° was preferred. For speeds of 20-25mph, the best riding position varied according to the event: in a steady-state endurance event a small torso angle was better; in sprinting or in variable conditions where more power is needed, a more upright position was better.
The conclusion that the most efficient riding position is not necessarily flat-out may be great news for triathletes who find extreme aero positions uncomfortable. However, that’s not to say a ‘sit up and beg’ position is super-fast – the highest angle used in this study (24°) is still quite low!
(Ref: J Biomech. 4 March 2014)
Takeaway tip: At 20-25mph, angle your torso around 8°. In hilly or windy conditions, adopt a slightly more upright position. Those averaging 18mph or less needn’t worry about adopting a very flat position.
(Main image: Rich Cruse)