Since the days of Arthur Lydiard, running coaches have recommended alternating hard-easy workouts as the best and fastest means of seeing improvement as a runner. In the book that he co-authored with Garth Gilmour, Distance Training For Masters (Oxford, England: Meyer & Meyer Sport, 2000), Lydiard stated that a runner using a hard-easy training system would achieve increased fitness three times faster than one who trained at the same level of intensity daily. Incorporating target heart rate zones into a training program simplifies the process of following hard-easy training systems by helping runners to choose the optimum training intensity for a given workout.
Defining Target Heart Rate Zones
Target heart rate zones quite simply are training intensities expressed as a percentage of a runner's maximum heart rate (MHR). MHR is the highest theoretical heart rate that a person could achieve in an all-out aerobic effort. Typically these zones are expressed as either four or five specific levels of training intensity. One four-zone system, as presented in Hal Higdon's book, Run Fast (Emmaus, Pa., Rodale Press: 2000) is as follows.