[Editor’s note: A reader submitted a question about training at your VO2max and how long you can actually spend training at that intensity.]

By Jack Daniels

Our research determined that a runner can run at VO2max for about 11 minutes, and certainly running at VO2max is associated with having a maximum heart rate. Trying to run longer at maximum HR will definitely be associated with an accumulation of blood lactate and personal discomfort. One could say that there is certainly an intensity of effort that cannot be held for more than about 10-15 minutes. Keep in mind that it takes a few minutes for your heart rate to reach its max, and during that acceleration time, lactate and discomfort are both increasing, eventually reaching an intensity that will promote a lower intensity rate.

The type of method used in monitoring HR can also cause trouble when using HR to determine training intensities. This is one reason why we came up with the VDOT system, because it determines speed of training for various types of benefits, and that may or may not always agree with what a heart rate monitor is providing you with. On the other hand, under windy, hilly or hot conditions, using HR to monitor effort can be better than going by a specific speed of running, as the work being done does not directly relate to speed.