Knowledge Level: Intermediate
A Member e-mailed us asking why we use a threshold heart rate test, rather than maximal heart rate, to calculate training zones and why the zones his Garmin unit gave different training zones to our online calculator.
Finding your genuine maximum heart rate requires a maximal effort to be accurate and the result can be affected significantly by how rested you are, if you didn’t sleep well or if you happen to be a little under the weather. More significantly, it requires a huge psychological effort to push yourself to absolute maximum and, if you happen to be lacking a little motivation or that masochistic streak on test day, your result will be skewed. Regardless of the protocol you use, it relies on a tiny snapshot of data when you’re at your absolute limit and replicating that moment accurately is almost impossible to do.
This is why a sub-maximal threshold test, taking an average of your effort over 20 minutes, is far more accurate and easy to replicate. It’s still a tough test but, because it’s not an all or nothing top end effort, dips in recovery, health and motivation tend to be ironed out. Threshold is the intensity you should be able to sustain for an hour’s effort but the calculation we use from a 20-minute test correlates very well and is a far easier test to motivate yourself for. From a sportive perspective, having a tested threshold is far more useful than a maximum. You should never push anywhere near to maximum in a sportive but threshold is your “redline number” that you’ll use to pace tough climbs. Also the training you’ll perform for a sportive will have little impact on your maximum heart rate so, if you rely on this figure for your training zones, they’ll remain fairly static. Your threshold will rise with the training you do, meaning you can ride nearer to your maximum for longer and, by regularly testing for your threshold, as prescribed by the British Cycling Sportive Training Plan, you’ll be able to adjust your training zones to account for this.
Don’t even consider taking the easy way out and using formulae such as 220-age to calculate maximum heart rate and then using that figure to work out training zones. The studies that were used to produce such formulas were typically conducted with sedentary populations and typically yield wildly inaccurate and low training zones. We’re all highly individual as athletes, so why would you have the same training zones as every other rider the same age as you? There are some formulae that also factor in resting heart rate but these are only a marginal improvement. Most heart rate monitors that offer an automatic zone calculation function use derivations of these formulae and should always be overridden and a custom heart rate zones setting used.
This reason above and the percentage bands used to calculate the zones explain why Zone 3 on your device, if automatically calculated, might not correlate to our Zone 3. Different models of heart rate training define their zones differently, use varying high and low percentages for each band and even have different numbers of zones. Our system, using a tested threshold to calculate the heart rate zones, has been found to be extremely accurate with our riders and is what we use for all our training plans. All the training sessions are designed with these zones in mind and, if you’re following the British Cycling Sportive Training Plan and using heart rate to gauge your effort, it’s essential for you to use it too.