This morning I was working my way through an early morning 14 mile run with some speed play thrown into the center of it. It was only 20 minutes of work but honestly, I think it is worth it to schedule this type of stuff during my longer runs.
First, it breaks up the run and gives the mind something to do other than just zone out. I mean how often during a long do people really change the pace that they are running. Using myself as an example, I would say that not many do.
Secondly, doing a little speed play during a longer run can help condition the mind to running at a faster pace while tired. One of the hardest things for any runner is to pick up the pace once fatigue starts to set in to the body.
Thirdly, one should mix up the speed play. Don't just do intervals where they are all the same length. Try a few longer ones and then a few shorter ones. The combination helps the body adjust to surging late in a run.
Forth thing and probably the most important part about adding this speed play to your longer workouts is once you are done and return to your previous pace, it feels so much easier. To the mind, it is like "why was I complaining about this being so hard" "This is really easy now". Those last couple of miles of the end will end up being the easiest and best of the entire run.
This is pretty much how my 14 miler went this morning. I headed out the door and about 5 miles into it I started my 1st of 4 sets of 3 minutes followed 2 x 1 minute with ½ recovery. The first one was tough but then the body and the mind settled into a rhythm and the rest were reeled off like clockwork. Some 20+ minutes later, I was over half way through my workout and didn't even realize it.
Thoughts from the Cool Down Runner