I believe the most misunderstood, or maybe just the least known of running workouts, is the Tempo Run. What is it? Why do it? What speed? What distance? What day of the running week?
There are as many different descriptions of a Tempo run as there are running books out there. But I'll make it simple. A Tempo run is any run that you do to build up your aerobic endurance. So anything just below your anaerobic threshold and above an easy run falls into this category. From our earlier discussion, you'll remember your anaerobic threshold is about 85% of your heart max rate. So I'm talking about a run at 70-85% of HMR.
So how much of your weekly run should be a Tempo run? I have one weekly run on Thursday that I classify as a Tempo run. I warm up for 1.5 miles [approximately 15 minutes] then watching my heart rate, try to keep 4 miles at 150-162 [my anaerobic threshold is 163]. I also leave the last two miles of my long run for this heart rate range. I do this to train myself to be able to push it for my planned half marathons.
I am very disciplined in regards to the 163 heart rate mark. As soon as I hit 163, I slow up immediately until it drops down to 155 before getting into the running groove again. It's important to not change this run into a speed workout [anaerobic threshold or above].
For those of you that have watched the movie "Chariots of Fire", I follow my 163 rule by remembering one of my favorite scenes in the movie. It is the exchange between Coach Sam Mussabini and Harold Abraham as he explains the concept of over-striding for the sprinter. As he describes the effect of over striding, he slaps Abraham in the face saying: "Remember, over striding. Death for the sprinter. (slap) Knocks you back. (slap) Like that! (slap) And That! (slap)
In the same way, going into anaerobic threshold when doing a Tempo run defeats the purpose of the Tempo run. Leave the anaerobic threshold workout with the speed workout. Your training is hard enough without blowing your aerobic endurance workout.
For those of you just getting started with the Tempo run, I have a great transition method for you to find your tempo pace over the course of the weeks in your first training plan. When I got started on Week One of my 12-Week Sub-2 Hour Half Marathon training, I do my 400 meter pace at 8:00 MPM (Minutes per Mile) and the Tempo Run pace @ 10:00 MPM. The 8:00 MPM for my speed workout doesn't change but my Tempo speed will. I run at the 10:00 MPM until I can do the full four miles at that pace. As soon as I make it, the next week I move up pace by 10 seconds. So in this case, it would go to 9:50 MPM the next week. Again, each week, I keep the pace until I see my heart rate reach 163 and then I back off. If I need to walk to get the heart down, I do it. But remember, no going over the 163 heart rate.
You may look at this plan and think, 'Can you really run a 9:09 pace during the Half Marathon when doing a Tempo run at 10:00 MPM in Week One of your training?' The answer is yes. What you will find is that each week your tempo pace will get easier and easier to reach. For example, I'm in Week 6 of my training and already up to a 9:30 MPM. By Week 10, I should be doing a 9:10 MPM. If you do find yourself in Week 6 not being able to move out of the 10:00 MPM because of the anaerobic threshold, this is God's way of telling you that you're not ready for a 2 Hour Half Marathon.
I hope this helps you incorporate Tempo runs into your weekly workouts. They're a great way to not only build your aerobic capacity but also give you a test run for your coming race.