WHY IS IT SO HARD TO ESCAPE THE MODERATE-INTENSITY RUT?

If a polarised-training method works and is practised by elite runners, why do so many competitive and recreational runners complete about half of their training at moderate intensity or faster? Stephen Seiler, an exercise scientist and researcher in Norway, suspects one reason is that the low-intensity zone is much broader for elite runners, making it easier to stay below the moderate threshold. For example, a 2:10 marathoner is likely to be below the first ventilatory threshold when running 5:40 per mile or slower, whereas a 3:30 marathoner may be above this threshold already at 8:05 per mile. A 10-minutemile runner’s low-intensity zone might end up being a run-walk, but that’s the level of easy work you need to do to build the lower end of your cardio capacity and still properly recover.

– Matt Fitzgerald