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Why Your FTP Score Might Not Be As Important As You Think For Ironman Athletes?

In recent years, the use of a power meter in cycling and triathlon has become more popular over the years as the affordability of the technology has meant that access to it is now easier than ever. This can be via a power meter on the bike or via a smart turbo trainer. Whilst for athletes and coaches this is an amazing tool for creating appropriate training stresses, race strategies and monitoring training load, are there downsides to it?

What is your FTP? So FTP stands for Functional Threshold Power, this is what you, in theory, can hold power-wise for a 1 hour best effort. Due to the effects of doing a 1 hour best effort, this is very rarely ever done so there are two tests used to predict this.

The first is a 20mins best test. This is exactly as it sounds, 20mins best effort, taking the average power measurement. Then to calculating your FTP at 95% of that score. So if you averaged 240w for 20mins, your FTP would be 228w.

The other is the Ramp test. This will start easy, then every minute will increase the power by 20w until you simply cannot keep going. This test tends to identify the upper limit of your aerobic capacity and will estimate your FTP via that. This test tends to be more appropriate for less experienced riders.

Now both of these tests will be done indoors. I know some people will use a 10-mile TT for a 20min power test, but with my sports science head-on, to make sure the testing environment is consistent and testing is comparable, indoor testing is the most appropriate. But now this is where the problems begin...

Is it transferable to riding outdoors?

Well here is where the problems begin, for some people yes! But for some people no!

Now there can be a few reasons for this, but the most likely one is their rider's ability to maintain a smooth constant pressure on the pedals. An indoor trainer is like riding on the smoothest road in the world. So if you're a rider who does the majority of their riding indoors or has learnt how to ride in a country where the roads are similar to this, then when they get outdoors on undulating roads or routes which you can find in the UK or across Europe, maintaining a smooth constant pressure on the pedals becomes difficult.

So if you've spent a large period training indoors, whether that's because of a cold winter or a ridiculously hot summer, there's no doubt that your power scores will go up and you will have made improvements in your cycling fitness. But just don't expect them to automatically correlate to the outdoors...

Is your FTP comparable to somebody else?

The simple answer is no! How your FTP compares to another ride is irrelevant. Firstly, the highest FTP doesn't mean they're the fastest. Secondly, power meters all read slightly differently and especially in different conditions. Plus you have to consider there are other factors here that make up speed. You have power-to-weight ratio and power-to-drag ratio are huge factors depending on the course that you're riding. Also, your ability to ride a bike, never underestimate the importance of cycling skills.

Triathletes, what should you consider?

If you're doing an ironman and you plan to use your FTP to help pace yourself around the bike course, then that's fine, but you need to also be very flexible on these numbers. Why? Well, you need to consider that on the day of an Ironman, you'll have had a broken/short sleep, a 3.8km swim before riding and factoring you still need to run a marathon also.

You also need to consider whether you're sitting upright or in an aero position for it. If you want to be better on your TT bike, then you need to be in aero but what about if you're preparing for a hilly ironman route which will require you to be in and out of aero and the saddle at times? How is this now relevant?

Can you see start to see why your 20-minute best effort can start to become a bit irrelevant? So let's think about the bigger picture. There is nothing wrong with developing your 20min, it can be the sign you're improving your fitness and potentially becoming a faster rider. BUT... there's a lot of hype about what is your FTP figure, so try not to get drawn into comparing with others. It's about balance, if you only want to improve your 20min power, then you will fall apart in the later stages of an ironman bike leg, and probably walk large parts of the run. So ensure your training makes sure that you can ride 180km at a good consistent power that is fast but efficient but then get ready to run a marathon, not walk it!

Happy Training!


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