The Benefits of Being Aero on the Bike

The Benefits of Being Aero

So, what are the benefits of being aerodynamic? 

It is worth noting that the latest research demonstrates that being aerodynamic has benefits at any speed, and any power output. Previously it had been the belief that the real aerodynamic benefits only kicked in when travelling at speeds in excess of 20mph.

In recent trials, our 70kg male cyclist riding at a constant power output of 300 watts on a flat road with no wind could save 6 minutes, 14 seconds by adopting a typical aero position as opposed to riding in a seated position with hands on the top of the handlebars. That equates to an increase in speed of approximately 4 km/h and would result in a time of 58 minutes, 29 seconds in an aero position as opposed to 64mins, 43secs sitting with hands on top of the handlebars. By optimising the aero position it is possible to reduce that time by a further 1min, 30secs to 56mins, 59secs. 

Further studies have shown that regardless of initial speed or power output any decrease in drag area will result in an increase in speed. Generally, going from riding the bike in a standing position to riding in an optimised aero position can increase velocity by about 20% (research has shown an increase in velocity of 19.4% for 100 watts and 20.4% for 400 watts).

The story is similar when it comes to riding on hills. On a 5% gradient an optimised aero position results in greater speed (0.6% at 100 watts, 3.7% at 400 watts) compared to standing or seated climbing. At higher power outputs you can see that the differences are more significant. As the gradient increases the speed differences between riding in the various positions becomes less. The aero position becomes less important on a 10% gradient and even less so on a 15% gradient. 

Further research has indicated that by riding uphill in a standing position, oxygen uptake is increased. The cost of this increase in oxygen use is a reduction in a riders’ maximal sustained power by approximately 17 watts. What this means is that there is a cost to standing that will affect speed – less power = less speed! Less powerful riders will be affected more so than more powerful riders – 17 watts represents 17% of total power at 100watts, whereas it is only 4% of 400 watts. It can be seen that it is more efficient, long term, to remain seated on a climb – especially if you are a less powerful rider. There will, however, be occasions where standing for short bursts is necessary, for example when there is a sharp “kick up” in the hill or if racing to cover an attempted attack. 

From the perspective of energy expenditure riding at any given speed you will preserve energy by being aerodynamic – something that will really benefit you when it comes to the run! 

The following table – again assuming our 70kg male cyclist – shows different energy expenditure when riding at different speeds, in different positions and different gradients.

Energy
Expenditure
at
Different Speeds
 Standing
(kcal/min)
Seated, hands on
brake hoods
(kcal/min)
Aero Position
(kcal/min)
Flat road,
no wind
   
Riding at
20 km/h
4.73.53.3
 25 km/h8.56.15.7
 30 km/h13.99.99.1
 35 km/h21.515.113.8
 40 km/h31.421.820.0
 45 km/h44.030.527.8
Flat road,
11 m/s
head wind
   
Riding at 20 km/h33.322.720.7
 25 km/h48.733.230.1
 30 km/h67.846.041.7
 35 km/h90.461.355.7
5% Gradient
uphill
   
Riding at 20 km/h20.519.319.1
 25 km/h28.225.925.5
 30 km/h37.733.632.9
 35 km/h49.142.841.5
10% Gradient
uphill
   
Riding at 20 km/h36.435.234.9
 25 km/h48.045.745.2
 30 km/h61.457.456.6

In summary the position you choose on the bike can affect your speed and therefore time taken on the bike leg, and/or enable you to preserve energy for the run. If you do decide to alter your position remember to change one thing at a time and make small, incremental changes not big ones!! 

Hopefully the information contained in this short article has been of use and has caused some thought about the position you adopt on the bike when racing triathlon.