I've had metabolic testing three times. I initially used it to determine my HR zones. and while I train now train with a power meter, I still find the data from the test useful. The physiologist who has worked with our team is very focused on metabolism, and sees great value in HR data as a measure how hard you are going. He looks on the PM as more of a "tachometer". I take a different nutritional approach than most, and do all I can to burn fat rather than glycogen. My diet is low carb high fat, and I rarely eat anything prior to or during a training ride. The result is that, even after long layoffs the last couple of years, I've kept my Metabolic Equivalency Point (the HR at which you start burning more glycogen than fat) way up the chart. Aerobically, I've stayed fit with very little training. More fit (aerobically) than if I had taken a different approach, anyway.

My last test was February of last year, and I had it done to assess the impact of my diet. My VO2 Max was 4.73 L/min, @ 360w. L/Min is the preferred measure, since VO2 Max is not directly related to your weight. My "MEP" was 138 BPM @ 210w, and my anaerobic threshold was 172 BPM @ 330w. I have a decent, but not extraordinary, VO2 Max. As has been said, there are far more important factors. Part of what I'm trying to do by pushing up my MEP is to save my glycogen reserves for when they are needed, at crunch time. There is a lot more that the nutritional approach offers (less lactate, less cell damage, quicker recovery) and all that seems to be working. I just haven't stressed it sufficiently because work and home life has made my training very sporadic. I don't know if my reduced glycogen stores will be a big limiting factor at the high end. Based on the training race a week ago, it's looking pretty good. I stayed in the lead pack despite my lack of training.