The aerodynamic drag of a cyclist in a time trial position is strongly influenced by the 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 in the UK have used computer modeling 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 28mph 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.
Conversely, for speeds below 19mph, a more upright position close to 24° was preferred. In a steady-state endurance event like a triathlon and at speeds of 20-25mph a small torso angle turned out to be 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’ position is super-fast – the highest angle (24°) used in this study is still quite low!
So, at 20-25mph, try to angle your torso around 8°. In hilly or windy conditions, adopt a slightly more upright position. Those averaging 18mph or less don't need to worry about adopting a very flat position.
(Ref: J Biomech. 4 March 2014)