fatassinyogapants wrote:
I hear lots of people saying easy runs don't improve fitness and/or are just for recovery. Does that mean doing 3 or 4 workouts a week and just having rest days in between would be equivalent to having 3-4 easy days and 2-3 workouts a week? Also, why do most elite distance runners run the majority of their mileage easy?
They have a whole host of aerobic benefits, such as increase of mitochondria, increased capillary density, increased mitochondrial enzyme activity, etc.
It takes anywhere from 5-10+ days to recover from a work-out, so if you do them too frequently, you'll either burn yourself out or you won't be able to do the work-out as fast. In either case, you aren't improving fitness.
It's counter-intuitive that a whole bunch of easy running makes you faster when you are going so slow, but any work-out's effect is a quality of intensity and time. A speed work-out is fairly low volume, but very intense, so it's a powerful stimulus. Easy runs are low intensity, but an elite runner may run 100mpw easy, so that's still a very powerful stimulus for adaptations for them.