This 28 Week Plan is designed for the Novice Runner (someone who has never run a 1/2 marathon before, or never run more than 3 miles consistently). Based on time and Heart Rate.
HR Zones (as used in this program) are based on Max HR.
Z1 (lo aerobic): 65% - 74%
Z2 (hi aerobic): 75%-85%
Z3: (Avoid this Zone!): 85%-89%
Z4: 90% - 95%
You can estimate your maximum HR by using the formula: 220 Minus Your Age.
"Long Runs" are on Sundays, and should be done without stopping to walk - keeping the HR in Z1-Z2.