Originally Posted by Carbonfiberboy

Firstly, going for 90% of MHR or whatever percent is a bit of a mistake. What you want is to be over your lactate threshold (LT) by some amount, which means first of all knowing where that is. There are tests to find it. Google or use the sticky on this forum. Among those who use power meters to determine the intensity of their efforts there's a concept known as functional threshold power (FTP), which is the power one can produce at or near one's lactate threshold. FTP has been found to be a better gauge of effort than HR because what happens in your legs during an effort starts as soon as you hit them, not when your HR reaches some certain level.

Your HR will always lag during hard short efforts. So say you do a hard effort of only 3 minutes. Your HR may only be over your lactate threshold for the last minute. However if you are holding a steady effort, you will be doing a VO2max interval the whole time, not only the time your HR is above LT. So use your HR to gauge the effort you are supposed to produce, but count the whole time of the interval during which you are holding the effort that eventually produces the desired HR. Note that if you are too tired from other recent workouts, you may not be able to reach this HR and thus should not be doing the intervals anyway.

Elite athletes using what is known as polarized training have found the most effective interval plan to raise VO2max is a set of four 8 minute intervals just over LT. There are many interval plans to choose from. See http://www.bikeforums.net/33-road-bi...cipe-book.html