Horseback riders are familiar with the phenomenon of the horse smelling the barn. As the horse and rider return to within sniffing range of the stable after a long ride, the horse spontaneously increases its pace to get the darn thing over with. Many human runners do something similar. When I took up running at age 12, I completed the same six-mile route every other day, and I always instinctively ran the last part faster, to get the darn thing over with.
Instinctive though it may be, picking up the pace in the last part of a run is not something that runners should do in every workout. That's because there isn't anything that runners should do in every workout. Training must be varied from day to day to develop well-rounded fitness. But there is a place in any structured training regimen for progression workouts, which is what coaches call runs in which the last part is run faster than the first.
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There are three distinct types of progression run that I like to incorporate into the training plans I design. Their benefits overlap to some degree, but to a complementary degree, the benefits of each are unique to that specific format. Let's take a look at all three.
A fast-finish progression run is a run in which the faster, second part of the run is relatively short—usually between one and three miles. Fast-finish runs may be either moderately challenging or very challenging. The factors that influence the challenge level of a fast-finish run are the duration of the slower first segment (the longer it is, the more fatigued you will be when you start the faster second part and the more challenging the overall run will be), the duration of the faster second segment and the pace of the second segment.
Easier fast-finish runs are a great way to give yourself a moderate training stimulus at times when your body is ready for more than an easy run but you don't want to leave yourself too tired to perform well in your next scheduled hard run. An example of an easier fast-finish run is five miles at a comfortable pace followed by one mile at 10K pace.
Harder fast-finish runs are great workouts for half-marathon and marathon training, because they challenge you to run fast when you're already tired. An example of a tough marathon-specific fast-finish run is 13 miles at a comfortable pace followed by three miles at half-marathon pace.
More: How to Run a Faster Marathon