Are “heart rate training zones” for real?
Running coaches like Roy Benson, Phil Maffetone, and John L. Parker, Jr. tell us to keep our heart rate at 65, 70, 75, 80, 85, 90, or 95 percent of max depending on our goal: easy recovery, endurance, “fitness improvement,” speed-endurance, speed/turnover, etc.
Inquiring minds want to know: Why these [...]