A lot of riders and coaches use the terms threshold, lactate threshold and functional threshold power interchangeably. They all describe the intensity you can sustain for a prolonged period without blowing up.
But how long is a prolonged period of time? One hour, twenty minutes, four hours? This is the problem – the length of time often isn’t specified. In fact, the amount of time that an athlete can sustain 4mmol/litre lactate concentration is different from athlete-to-athlete and depends on how fit they are.
In the real world, there are a very limited number of coaches and athletes who use blood lactate levels as a training tool. This would require standing at the side of someone while they do their training, taking regular blood samples and testing them… hardly practical!
This is where FTP comes in. This is the power you can sustain for one hour – regardless of lactate concentration in your blood – and it’s a very useful landmark in determining training zones, which in turn will allow you to control and measure how hard you are riding, thus giving you the ability to target specific improvements in your form. Refer back to my article on training zones to find out more.
Lots of riders train with a power meter (or heart rate monitor) and, therefore, it is relatively simple to measure the power you can hold for one hour – simply go out and ride hard for an hour!
In practice riding at your limit for one hour is very tiring, requires an element of pacing and doesn’t fit particularly well into a training plan. But we cheat somewhat by doing a 20-minute test, from which you can take 95 per cent of the figure as a best estimate on what would be sustainable for one hour. From this figure you can also work out your training zones – you can read all about training zones here.
A good warm-up is important and then you need a section of road twenty minutes long. Set off at a pace you feel you can just sustain for the full 20 minutes (this is probably slightly easier than you think) and aim to hold this intensity for 17 or 18 minutes, at which point give it everything until the end. You need to record your average power and average heart rate for the 20 minutes. To calculate your FTP take the power and multiply it by 0.95. Do the same for your average heart rate to calculate your threshold heart rate.
Now you know what lactate acid is, and you know your FTP, what can you do to improve it? After all, the higher your FTP, the more power you can sustain.