This is an 11 week half marathon training plan where the training intensity is based on Power rather than pace or heart rate. Power is measuring the effort you are putting in as you run. Running up a hill or into a headwind requires more effort – power number increases at the same speed, and of course power number decreases at the same speed as you run down a hill, so you would slow down up a hill or speed up down a hill to maintain
the same power level.
The target intensity is a percentage of what is known as your Critical Power