Remember that you only lose about 17 seconds when you walk for a minute. The small amount of distance you lose on extra walking earlier will almost always be recovered at the end – because you kept your legs fresh. Those who put this concept to the test almost always find that taking more frequent walk breaks doesn’t slow the overall time of long runs – when the long runs are done at the correct slow pace.
You can’t run too slowly on the long runs. Run at least two minutes per mile slower than you could run that distance on that day, accounting for heat, humidity, etc. You won’t usually feel bad when you’re running too fast at the beginning of the run so you must force yourself to slow down.
Walk breaks on long runs must be taken early and often to reduce pounding and fatigue. Walk breaks allow the primary running muscles to recover fast – even when increasing long run length. Walk breaks on long runs will also help most marathoners run faster in the marathon itself.
The most important walk breaks are the ones taken during the first mile and the second most important set, those taken in the second mile, etc. When taken from the beginning of all long ones, walk breaks erase fatigue, speed recovery, reduce injury, and yet bestow all of the endurance of the distance covered. In other words, a slow long run with walk breaks gives you the same distance conditioning as a fast one, when both cover the same distance.