I’m a triathlete, which means I need to get the best out of the limited time I have to train in the three sports of swimming, cycling, and running. When I race, I have to be able to excel in all three, so that is why I recently got a VO2 max running test, a test that measured my oxygen intake as my exertion on the treadmill intensified. (Basically, I ran on a treadmill while wearing an oxygen mask.) The test identified what my heart rates are for the standard training zones, i.e. aerobic threshold, lactate threshold etc. Running with a heart rate below my anaerobic threshold ensures that I’m using my body’s fat reserves, which enables me to keep going for a long time. If I go above that heart rate, my body goes anaerobic and starts to use my limited sugar reserves. Knowing what’s happening to my body in this capacity during an endurance event makes a huge difference to my performance.

Without clinical testing, the most common way of determining your anaerobic threshold (AT) is to subtract your age from 180. In my case, this number would be 139. That means that my AT should be at a heart rate of 139. However, the VO2 max test showed me that my actual AT is 155, a big difference!

The idea is to develop your aerobic capacity by running at your AT without going anaerobic. It is recommended that in training, you use the 80/20 rule—that is, 80% of your runs should take place at your AT and 20% should be spent doing intervals, i.e. higher heart rate workouts. Training in this way will increase your endurance, enabling you to ultimately go longer and faster.

Since the 80/20 rule can significantly increase your endurance, you can see why it’s important to have the actual heart rate numbers as opposed to the rule of thumb numbers, which in my case were nowhere close.

If you’d like more information about VO2 max testing or would like to sign up for your own test, I highly recommend dhp (diaz human performance).