The Purpose of Progression1 of 5
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.
As a broad guideline, I recommend that all runners include at least one progression run per week in their training at all times. Always choose the specific format that fits best with your immediate training objectives.
There are three distinct types of progression runs that I like to incorporate into the training plans I design.
Fast-Finish Run2 of 5
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.
Threshold Progression3 of 5
A traditional threshold run consists of a short warm-up followed by a few miles of running at "lactate threshold pace" (or the fastest pace you could sustain for one hour in race circumstances) and concluding with a short cool-down. In a threshold progression, the warm-up is greatly extended and the cool-down is removed.
The purpose of these changes is to create a workout that challenges you to sustain your threshold speed when you're already tired. This makes it a great workout to use in half-marathon and marathon training. An example of a threshold progression run is five miles at a comfortable pace followed by four miles at threshold pace.
At this point I would like to pause and answer a question that may have popped into your head. "Isn't it bad to finish a workout without cooling down?" Actually, no. The notion that concluding workouts with a short period of low-intensity activity promotes faster recovery is mythical. Research has shown that cooling down has no effect on recovery, so it's OK to skip it in certain workouts. (Warming-up before high-intensity exercise does accelerate post-workout recovery, however.)
Marathon-Pace Progression4 of 5
Marathon-pace progression runs are an effective means to increase the challenge level and race-specificity of long endurance runs. Many runners make the mistake of doing all of their Saturday or Sunday long runs at a moderate pace, but once you have used these runs to develop sufficient raw endurance, they don't provide any further benefit unless you pick up the pace.
You don't have to be training for a marathon to benefit from marathon-pace progression runs. They provide excellent aerobic support for any race distance, although you will want to use them differently depending on your specific race distance. If you're training for a 5K or 10K, marathon-pace progression runs should be emphasized relatively early in the training process and then phased out in favor of long runs that include even faster running.
If you're training for a half-marathon or marathon, they should be emphasized later in the training process, and they should be longer. A good peak-level marathon-pace progression run, appropriate for three to four weeks before a marathon, is two miles at a moderate pace followed by 14 miles at marathon pace.