I was wondering, how exactly I can read te HR Curve Chart to “check that my VO2 max intervals are working” (as the help text reads below the chart)? What would I have to look for? Are there example charts that show VO2 max intervals that work or do not work?
One way people measure the “success” or otherwise of vo2max intervals is time spent at high heart rate (more than 90% of max). The chart makes it easy to check that. So you can try hard start intervals and see if that bumps up that time for the same interval set etc etc…
As David has mentioned, when you are rested, your heart rate should respond quickly when you do sustained intervals above threshold, eg. 4-5 sets of 3-5 minutes all out efforts. When fatigued, your HR will respond slowly, and sometimes it doesn’t even get to the level you would see when fresh. You might hit the power target, but it feels harder than it should; indicating you aren’t ready for this type of work.
So I would be looking for accumulated time in HR-Z5 or HR-Z6 to be somewhat similar to the time spent in the VO2 Max Power Zone? I could compare HR Curve with the Power Curve and look for similarities?