Since coming back from Disney, I have not been doing any interval training runs. Why? Well, initially I was in my recovery period post-Disney as I was trying to rest up prior to the Polar Dash Half Marathon two weeks later. I did not want to do too much running and risk an injury that would prevent me from running that race. All I did between those two races were easy and long runs. Besides, I figured I deserved a rest after all the training and races leading up to Disney.
Then February hit. And I thought "Why not just ease into training instead of picking up where I left off?" Well, that thought did not last long as I watched others in my W.I.S.H. racing team really getting their "Grrrrrr!!!" on and being seriously focused on making 2012 a great improvement year for them. But even as I started my training again, and setting my Long Run distance minimum to 8 miles, I hadn't fully laid out a real training plan. And, my experimentation with minimalist shoes changed my routine up a bit.
But after 62 miles, and no run really going below a 10:00/mm pace, I decided that I need to bring the interval runs back if I am going to meet my goal of PRing my March 5K with "The Penguin" John Bingham. Not to mention my goal of finishing my first Full Marathon in under 5 hours.
So this morning, I ran intervals on the Treadmill for 3.40 miles. I spent 38 minutes, doing sets of a 9:15/mm pace for 1/3 mile followed by a 1-minute recovery run at 11:00/mm pace. The fast run segments were all in the lower range of my Zone 3, which I was happy with. I will be happier when I can do them in Zone 2 because that will show that my body has acclimated well to that pace.
Interval training is a key way to improve your speed over time. The idea is not to overstress yourself or run at some blazing/sprint pace, but to pick a challenging pace -- maybe 20-40 seconds faster than your usual average race pace -- and run at that speed for a speciifc distance (anywhere from 1/4 mile to a full mile). Then slow down to a recovery pace -- the recovery run segment is as important as the speed segment! And you do that for a set of three. (Why is recovery important? Because you are not only training your body to run at the elevated pace, you are also training your body to reduce your heart rate more quickly, thus improving your recovery time overall.)
Then I insert a 5-minute easy run segment before I repeat the entire set of three again. You can do three sets in one Interval Training run (today I only did two sets of three because I got started late and had to go to work). Some people do more.
Of course, before and after any workout, you need to do a proper warm-up and cool-down. I usually do a 5-minute warm-up walk at a 17:00/pace (3.5mph) and a 5-minute cool-down. And then, remember to stretch and foam roll when you are done. Your legs will love you for it later.
One other thing about Interval training. Decide which is more important: speed or endurance/distance. You can increase your pacing as you become more comfortable with the current pace of your speed segments. And, you can increase the distance at which you run your speed segments. But I would recommend not doing both at the same time. Work on one or the other.
For example, you might work on speed for a while, increasing your pace by 20 seconds at a time as you become more comfortable with your speed segments. But keep the distance of those segments the same. It will help you to gauge your progress with your pacing. Then maybe after you are at a good pace, now start to increase the distance of your speed segments to see if you can extend your endurance at that pace.
Then once you are maybe running a 1/2 mile at that good pace, you can go back to increasing your pace. Some people return to their original distance when they make a big pace increase, and repeat their speed interval training. Others might try to increase their speed while staying at the higher distance. See what works for you. But if the new speed is too hard to maintain at that higher distance, back off on the distance in favor of the speed work. You can always increase your distance once you are comfortable with the higher pace.
But most of all, enjoy your interval training! And reap the rewards!