There seem to be two approaches to training for speed: tempo runs and intervals. Intervals get your heart rate into its anaerobic zone, while tempo runs hit your “threshold” aerobic pace (almost anaerobic).

I’m a bit confused as to how to implement both of these techniques, however.

First, high-intensity interval training is supposed to hit 70% – 90% of your maximum heart rate during the “work” period. But 90% of my max HR of 190 is 171, which is well within my aerobic zone. Things only start getting seriously anaerobic at around 185; at least in the sense that I seem to be able to run at below that pace (under serious chest pain 180+) for at least a few minutes. So does that mean I need to up the intensity of my intervals from 171 to 185+, to keep them anaerobic?

Second, I often get my HR up to around 180 on runs. This seems close to anaerobic, and definitely higher than the “tempo” pace mentioned on Strava (153-169). I’m torn between the definition of a tempo run as one that is run at your threshold anaerobic HR, and one that seems to agree with things I’ve read elsewhere.

So the questions are: do I speed up my intervals, and/or do I slow down my tempo runs?