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Thresholds Explained (Pt 3)

The last 2 weeks have been all about lactate threshold, anaerobic threshold and ventilatory threshold. This week, we're talking 'functional threshold' which is a term more commonly used amongst cyclists in particular.

What is functional threshold?

The clue is in the name 'functional'. The lactate / anaerobic / ventilatory thresholds are all valuable physiological markers but what's their practical use? A cyclist riding a time trial really only needs to know one thing, how much power can they sustain for the full ride. The more power they can sustain, the faster they will complete the course.

There is often a misunderstanding with regards to lactate / anaerobic threshold. If you visit a lab and have your lactate threshold measured, that doesn't tell you the power or speed you are able to sustain for a long period of time. To find the answer to that question, there is a more simple / practical / functional approach. Simply get on your bike and ride as hard as you can for an hour, then you'll know the answer.

Functional Threshold Power

The FTP is a real 'buzz term' in cycle coaching and I'm sure most cyclists and triathletes will have heard it mentioned by someone at some point! FTP is quite simply the highest amount of power you can average for an hour. To complete this test, you need a power meter on your bike or turbo trainer.

Riding for an hour on the turbo is a killer!! So to get round that, most people complete a 20 minute test and take the average power reading. If you then calculate 95% of that figure, that's your predicted FTP (average power for hour). For example:

1. Bob completes a 20 minute maximal test and averages 250 watts.

2. 95% of 250 = 237.5, this is Bob's FTP and what he should be capable of holding for an hour.

Is this just for cycling or can it be used for running and swimming?

The issue with running and swimming is that you don't have access to power data, so you can't calculate the figures as you can with cycling. Having said that, the functional threshold is really just a 'practical test' to calculate what you can hold for a period of time.

Swimmers will often complete a 'critical swim test' which is basically the same thing. The test is simply swimming as far as you can in 20 minutes. For running, the same applies, you could complete a 15-20 minute test and measure distance on the running track.

So why are functional tests popular?

They're popular because they are very practical. If you want to find out how fast you can complete a 25 miles time trial, the figure which is most likely to give you the answer is how much power can you average for an hour. Doing a lab test to calculate your lactate threshold or anaerobic threshold is valuable and useful for many reasons, but it will not give you the answer to the above question. Ultimately, functional tests tell you how fast you can swim/cycle/run for a set peiod of time and that's the best indicator of race performances.

If you'd like a more accurate assessment of your personal strengths and weaknesses, you can book a sports science assessment. We can put together a plan which will be specific to you, the cost for sports science assessment is £75 and you can BOOK HERE.

Marc Laithwaite
The Endurance Store

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