And when does the obsession cross the line





See you later watts per kg – why this dangerously obsessive measurement needs to stop being the unit to optimise.

Pretty much every cyclist has considered their watts per kg. In the cycling world where social norms are somewhat distorted, it was once commonplace to introduce yourself with your name, followed by your latest FTP in watts per kg. That was the degree of importance of this measurement. All across coffee shops in London, cyclists discussed this number at length, comparing themselves against their skinny friends who hit dizzy heights by being light. 

I cannot deny I joined the cause. Being female and around 55kg, I was always keen to play the watts per kg card as soon as the post ride chat turned to ‘Top Trumps’.  But how much does it actually reflect on the road? When is it a useful measurement? And when does the obsession cross the line into actually being dangerous for a rider’s health? I am absolutely no specialist nor medical expert, but it is very clear that this metric is going out of fashion, and for that, I am grateful.

So, to back track. What are we talking about here? Watts – a measure of power, which is in essence the amount of work done, divided by your mass in kilograms. Let us say you produce 250 watts for 20 minutes and you weigh 70kg, your watts/kg is 3.57 for that 20 minutes. To increase this number, you must either increase your power, or decrease your weight. Simple in mathematic terms, but in the real world, both elements are hard to achieve. 

However, perhaps you need not stress as it is not the ‘be all and end all’ of going fastest, and this is what we need to move away from. I’ve experienced several hill climb seasons where this number is the holy grail to maximise. I’ve seen friends, competitors and more worryingly, juniors, obsess over this number and enter into what can only be described as a starvation phase in order to ‘make the weight’ for hill climbs. It’s actually scary to witness, to see young cyclists, male and female, strip fat off to the bare bones in order to up their watts/kg. It’s incredibly unhealthy and it’s something we as a cycling community need to discourage.

So, what else is a factor? Well, aerodynamics for one. I ride the fastest road bike in the world. The Cannondale System Six. I would opt for this bike on almost any terrain as it is just so damn fast. But it is not that light. Coming in at just under 8kg you might think I’m mad to take it to the mountains, but the gains I get from how aero it is far outweigh the extra little bit of weight. That alongside all the energy saved in the lead up to the climbs by cruising along a whole lot more effortlessly, means that when I get to the hills, I actually have some legs for it. There is no point being a good climber if you’re spent before you get to the sharp end. 

In a road race, you’re going to get a mix of up, down and flat. On the flat your watts per Cda is way more important than your watts per kg. You want to be using as little energy as possible during the race so you can actually fire when the time comes. It’s only when you hit slopes around 8% where the importance of these metrics flips over to the advantage of lighter riders. Up to this point, your Cda is crucial, so spend some time looking at this and don’t think it’s just time trialist that should be interested in how aero they are. For example, the tyres you chose to run in a road race could make up to 20 watts difference in how much energy you need to just make your wheels roll. I would personally like to work 20 watts less than the girl next to me while we twiddle along the flat, knowing I have that in my pocket for the climb. 

There are so many things you can do to improve your Cda on your road bike. Like so many, that are a lot easier to achieve than upping your power; and I’m not saying stop training – or suffering calorie deficit during the season to desperately lose weight before a race. 

The other big factor is racing smart. I’m sure you’ve noticed it before, there are some riders who seem to do unbelievably well and get mega results with really fairly normal power numbers. These riders are just bloody good at racing. Positioning is a huge factor of how to race well. Not just to help keep safe, but if you can position well to ensure you ride the wheels, don’t take the wind, don’t waste energy chasing back on and closing gaps, you can cruise your way round a road race with the riders who’s watt per kg or watts per Cda or generally just watts, far exceed yours. 

It’s an art and I am in awe of the riders that have this nailed. That, as far as I can tell, is what makes you a truly amazing bike rider. I’m so fortunate that on the team this year we have a number of girls who fit this category, so my obsession is not with Cda or weight, or power, it’s to be a sponge and soak up all the experience and advice I can from those around me so that I do it better. 

There is a magnitude of detail omitted here, there’s a million scenarios to discuss, dissect and prove for and against, but this is it in a nutshell. If you take something away from this, let it be this – obsessing over your weight is for the most, a waste of time. Think about how you can go faster and how you can race better. Think about your kit; what you are wearing, what you are riding, how you are sitting on your bike. Think about your positioning, think about how you can get from A to B using the least amount of energy possible but with the maximum speed. Ok, so we aren’t racing right now, but go and target segments on Strava and try beating your own time, but focus on how you can be more aero or how you can push harder on the steeper bits and recover more on the descents so you use your energy better.

All in all, just think. And have that piece of cake.