Functional Threshold Testing - Heart rate and Power
Bike Test - If you only have a Heart Rate Montior
Functional Threshold Heart Rate (or FTHR) is the heart rate you can sustain for a one hour race effort. We use this heart rate as a physiological marker, from which we can work out certain zones with definite training purposes. For accurate heart rate based training, the first step is to accurately measure your functional threshold heart rate.
If you have a heart rate graph from a one hour race (like a cycling time trial), your heart rate average over the hour is your FTHR.
To test in training it's too hard to do an hour alone, so we use a 20 minute all out effort - ideally on a turbo trainer. Your FTHR is the average heart rate for those 20 minutes.
An ideal ride will have you riding at a constant speed through the whole test. This will 'feel like' an increasing effort, and be very challenging for the last ten minutes.
Bike Test - If you have a power meter
The good news is that the test is exactly the same! The only difference is that afterwards, when we look at the power data, your Functional Threshold Power (FTP) is 95% of the average power over the 20 minute test. So, for example, if you had an average power of 200W for the 20 minutes, your FTP would be 200 x 0.95 = 190W. You would then enter 190 into the ‘threshold power’ box under ‘power zones’ in TrainingPeaks. You can watch the video for more a walkthrough of how to do this.
Again, we're assuming that you've held a consistent power through the test. Wear your heart rate monitor as well, as this information will be valuable to your coach as you do analysis.
How threshold 'feels'
It's worth noting that most people can 'feel' Functional Threshold quite accurately, even without a heart rate monitor. It's that feeling of 'if I go a little bit harder, I'm going to have to stop exercising a whole lot sooner.'
However, in a race situation, when we're excited and our body is full of adrenaline, it's often hard to 'feel' things accurately. Similarly, in training, on your own especially, a heart rate monitor can be a useful tool to let you know that you should be working a bit harder in order to get the training effect you're after!
Powermeters can be very valuable in racing as the numbers never lie. With heart rate monitors, they often don't tell the whole story. They're affected by dehydration, tiredness, fatigue, whether you slept well, and most critically - excitement. The adrenaline of a race can make the numbers do funny things. You can see higher numbers than usual, yet feel great.