Power vs aerodynamics: how to get the balance right

Our very own British land speed record holder assesses the interrelationship between fitness, aerodynamics and power to establish your perfect riding position

(Image credit: chris catchpole)

At normal, everyday riding speeds, around 80 per cent of power produced by the rider is spent overcoming aerodynamic drag, so the importance of optimising your equipment, clothing and, most importantly, riding position can’t be overstated.

Too often overlooked is the fact that holding the most aero position places huge, highly specific demands on your body: aerodynamics and fitness are intrinsically connected.

No longer a luxury reserved for top-flight professionals, this interplay between aero and fitness must be a priority for anyone who wants to ride faster.

The perfect positions of pros like Bradley Wiggins, their backs perfectly flat, naturally rouse our envy and awe, but is it realistic for us to emulate them? How do you strike the best balance between a super-aggressive riding position and the ability to produce power?

Push too far in the direction of extreme aero and you will inevitably go slower through making it harder to pedal.

How much power output did Bradley Wiggins sacrifice to achieve the perfect riding position? (Credit: Watson)
(Image credit: Watson)

Pushing the limits

As the British land speed record holder for human-powered vehicles, I understand the importance of the role that aerodynamics plays in riding faster. My British record for unassisted top speed currently stands at 76.59mph.

At that speed, overcoming aerodynamic drag is the most essential piece of the puzzle. Luckily I had a team of engineering students and the might of Liverpool University behind me.

What tools are at the disposal of the average rider on a more conventional machine?

>>> Should you slam your stem: yes or no?

Many people experiment with aero positioning and take it too far. At some point, usually after slamming their stem and folding themselves in half, they experience a significant reduction in their ability to pedal hard and produce power.

In my day job as a cycling coach, I help everyday riders improve their fitness as a top priority.

Fitness remains the largest area of improvement for the vast majority of riders; hardly anyone, except full-time professionals, gets close to their genetic limits.

No matter how aerodynamic you are, you can’t go fast without pedalling hard. There must be compromise.

The fastest equipment is a very personal proposition (Credit: Fowler)

Most of us can afford a small sacrifice in power so long as it’s swapped for big reductions in drag. There is good reason that most hardcore racers don’t sit bolt upright on their bikes.

I asked Dr Xavier Disley, director of AeroCoach, whether it was more important to save drag or increase power.

“In a strict one-to-one [ratio] scenario, saving 10 watts in aero drag will increase your speed by the same amount as pedalling 10 watts harder,” he says.

“The first thing to note is that your aerodynamic drag wattage savings are scalable to the speed that you’re riding at.

"The higher the rider speed, the more impact small changes in your own aerodynamic drag - called your CdA - will have on wattage you save.”

Watch: Which faster - climbing in or out of the saddle?

At high speeds, a slight aero improvement makes a dramatic difference:

“At very high speeds [above 34mph], tiny changes in CdA/aerodynamic drag will have around 1.5 times the impact they would have at 25mph. So aerodynamic improvements net a greater wattage saving.”

This might lead to the conclusion that aerodynamics is of interest only to faster riders. But you’d be wrong.

Slower riders are out on the course for longer periods of time and wind hits them at a wider range of angles.

“Even a one watt reduction in drag over an Ironman course at low speeds can equate to up to a two-minute time saving,’’ says Disley.

So if aerodynamics is a concern for both slower and faster riders, who should be paying more attention to improving their power?

A highly trained rider will find it far more difficult to increase their sustainable power output by 10 watts than would a weekend warrior who is yet to add structure and periodisation to their training.

Aero gains are up for grabs for everyone.

Dan Bigham sharing aero secrets (Credit: Fowler)

Triple national track champion and head aerodynamicist of WattShop, Dan Bigham, has strong opinions on this topic.

“Aerodynamics don’t adapt to training stimulus, whereas your fitness does,” he says.

How did Bigham apply this principle in preparation for the National Track Championships?

“Ideally you would perform physiology tests in a range of positions, but the repeatability of a maximal effort is low. The ultimate goal is to know the most aerodynamic position you can possibly achieve so that you have something to aim for.”

>>> At what point do aerodynamics become more significant than weight?

Knowing your ideal position gives you a useful benchmark.

“Even if you can’t hold it now, you know which direction you need to go and what you need to improve in the future, be that shoulder, neck or hip flexibility.”

With skinsuits, wheels and bikes not coming cheap, picking the fastest bit of kit in the box sometimes feels more like a lottery than an informed decision.

Watch now: How much speed can you buy?

Bigham advises: “Equipment selection is very position-dependent to each individual. The air flows differently around everyone and every set-up, owing to their unique differences in body shape.

“There isn’t a one-size-fits-all solution. The key is to find a way of testing what works best for you and gather data to prove it. Don’t be taken in by unsubstantiated marketing hype.”

This doesn’t mean firms are innovating unconstructively.

Brands are moving their thinking towards creating different clothing optimised to an individual or event to make sure it truly is the best for them.

There are many options out there that will help you definitively test your aerodynamics, some of them eye-wateringly expensive.

Wattshop provide a more reasonably priced offering for aero analysis (credit: Fowler)

The physiologist’s view...

Dr Simon Marwood, senior lecturer in physiology at Liverpool Hope University

“Producing optimal power at the pedals is inextricably linked to riding position.

"Functional Threshold Power [FTP] is a close approximation of the upper limit of the physiological steady state. At this threshold, a steady state is achieved for oxygen uptake, blood lactate and energy provision.

"Above the lactate threshold, there is reliance on anaerobic metabolism to meet the energy demands of exercise.”

A hunched-over position can affect this by closing your chest, squeezing your shoulders together and tucking your chin, reducing your ability to uptake oxygen, thus lowering your threshold.

Extreme positions lead to extreme pain faces (Credit: McCandlish)
(Image credit: Andrew McCandlish)

"Above FTP, a physiological steady state is unattainable; blood lactate and oxygen uptake rise inexorably until maximal oxygen uptake [VO2 max] is achieved.

"Shortly, fatigue ensues and it is necessary to drop below FTP in order for exercise to continue."

Keeping your FTP as high as possible therefore delays the excruciating demise of your legs. Set too extreme a position and you will drift into ‘the red’ — the anaerobic state — sooner than you need to.

The bottom line is, small aerodynamic gains are worthless if they result in a significant drop in FTP.

>>> Is heart rate training still relevant in the age of the power meter?

My view as a coach…

Think of your goals when you consider bringing aerodynamics into the equation. Start with the easy improvements: tight-fitting clothing, reducing your frontal area, using deeper-section wheels and helmets designed to be aerodynamic.

Aero trumps weight in all but the most severe parcours.

So spend less time being a weight weenie and eating salads and more time working on being able to hold an aerodynamic tuck and fuelling your training correctly in order to increase power output.

Improving aerodynamics should be higher on your list than cutting calories
(Image credit: www.timeincukcontent.com)

There will be a point where you push your riding position too far. The only way to discover this is through fitness testing.

Use a power meter to test your FTP in a comfortable upright position where you can breathe deeply and move freely; this serves as a benchmark for your current physiological maximum.

If the results of the test say that your FTP is 250 watts but you can only hold this power output for five minutes when riding on the drops or the aerobars, you immediately know your power has been compromised.

Your FTP should be sustainable for between 45 and 60 minutes.

>>> Watch – Training zones: what are they and why do they matter?

If you don’t fancy continual FTP tests, use interval sessions to judge how difficult it feels. Feel is very important, but use all data at your disposal: power, heart rate and perceived exertion.

My top tip for adapting to an extreme position is to build things up slowly. Start by riding in a comfortable position during your warm-ups and only using your aero tuck while completing your hard efforts or intervals.

This will help you to hold your position and stay focused on not letting it slip.

Remember, riding at 10mph or slower, aerodynamics is not so important, whereas if you find yourself riding at speed into the wind, it’s time to drop some aero bombs.

Try to ensure your FTP does not slip more than 10 per cent through a change in riding position; from there, aim to adapt and eventually close that gap.

Peter Sagan proving that at super high speeds, position is more important than power (Credit: Sunada)

The bike-fitter’s view

Tweaking your riding position unsupervised is a risky business. Here, Retul master Garth Kruger of Vankru Cycles sets out the priorities:

“85 per cent of people who visit us for a bike-fit are triggered to do so by an injury. So, injury prevention and comfort are higher priorities than aerodynamics for us.

“The challenge for a bike-fitter is that what’s aero for one person isn’t necessarily as aero for another, but there are general principles to follow. Educated guesses can be made, but without the appropriate equipment, it will always be a guess.

“The biggest limiting factor in how aggressive a position a rider can hold is their flexibility and core strength. Improving shoulder, hip flexor and hamstring flexibility will also get you closer to your dream position.”

Knee pain can arise from incorrect bike fit

Always begin with the expert advice of a bike fitter

Is your riding position too extreme? Here are Garth's top warning signs and advice.

Heads up

“You should be able to hold your head up comfortably for the duration of your event without pain.”

Back pain

“If you're getting lower back pain after an hour, something needs to change. Take a look at the range of motion in your hamstrings and hip flexors, as these areas are often the cause of the problem.”


“In a poorly-fit position you may experience pain if your shoulders are supporting your weight. Often we see people who can’t ride in their aerobars for more than five minutes without shoulder pain.”

The cost of pain

“If you sit up to alleviate the pain, then the time lost from riding in an upright position with poor aerodynamics will far outweigh any gains you could have made from your extreme position.”

Preliminary self-testing

“Before focusing on aerodynamics, try to ensure that you are ‘functionally adequate’. This means you can perform a deep single-leg squat, hold a plank for at least one minute and touch your toes while keeping a flat back.

"Only then are you likely to be able to tolerate an aggressive riding position. If you can’t complete these exercises satisfactorily, you should start with comfort as your primary goal and aero in second place.”

Making the choice

Ask yourself: does my aero-power balance need attention? Like many key questions in cycling, there is no straightforward answer.

To determine if you have found the right balance between power and aerodynamics, you need to address your goals. If you are riding purely for the enjoyment of the sport, then putting yourself through the arduous task of examining your aerodynamics will not fill you with the joys of spring.

However, if you have even the slightest concern for speed, performance or completing a tough personal challenge, aerodynamics should be near the top of your list.

Developing power in an aero tuck and dedicating hours of your life deliberating over equipment selection is less fun than just riding your bike.

But if your goals are to ride faster, then the value of achieving a super-slippery aero position is unquestionable.

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