The purpose of tempo interval training is to build your ability to run comfortably at your current race pace for the first half of your goal-race distance. In other words, you’ll always have a particular goal race distance for every interval workout. And the pace you’ll train at for the tempo intervals should feel comfortable on this scale: very comfortable, comfortable, tolerably uncomfortable, uncomfortable, and very uncomfortable.
The most difficult part of long-distance racing is to pace yourself so you finish without a crashing slowdown. Crashing is undesirable because it is very uncomfortable and it results in a slower finish time than you would have hit by pacing yourself correctly. Correct pacing, by contrast, is reaching the mid-point of a race still feeling comfortable. Then, as fatigue sets in, discomfort rises as you continue at, or faster than, your first-half pace. Discomfort during the second half of any race is an expected part of the endurance racing game.
During our annual BC Endurance training program, we train for three racing distances at different times of the year: 10K (Jan-Feb), half-marathon (Mar-May), and marathon (Aug-Dec). Thus, your ability grows from year to year as you cycle through the shorter/faster to longer/slower year-long training progression. With regard to tempo training, there are two ways you’ll know your tempo ability is growing: 1) you get to the mid-point of your races having run faster than previous races, but you still feel comfortable; and 2) your interval times get faster at the comfortable level.
“A ‘good workout’ is one where you have more energy at the finish than the start. A workout is basically a long warm-up in which your capacity for exertion expands.”
Your heart rate (like comfort/discomfort) is another measure of exertion. But there is no standard heart rate for interval measurement purposes because most people have different maximum heart rates. Nonetheless, you can take your heart rate immediately after every interval to provide a tempo exertion standard for you specifically. To identify improvement, what you’d look for over time is a faster interval pace at the same heart rate. A rising heart rate at a constant pace is also useful for determining when to end a workout.
Some athletes claim the tempo workouts are so easy they don’t get a “good” work-out. That’s because they either aren’t running the intervals at their race pace or they aren’t doing enough intervals. From a coach’s point of view, if you improve without injury, the workouts are optimal. But if you want to know whether to add duration to your workouts, you’ll need to know when to end them so you don’t over train. Here’s how.
A “good workout” is one where you have more energy at the finish than the start. A workout is basically a long warm-up in which your capacity for exertion expands. The moment fatigue sets in, capacity contracts and you stop improving. You can measure the point fatigue sets in by noticing when your heart rate rises at the same pace. That’s the time to end the workout. Or would you rather finish what you have scheduled while increasing your risk of injury and lengthening your recovery time from the workout?