Mile and mile-and-a-half intervals are one of the must-do workouts in the last couple of months leading up to big races. Most of us have a love/hate relationship with them. We love the adrenaline and endorphins while running, and that giddy feeling of accomplishment when done. But they hurt--lactic acid buildup in the quads, heart rate in zones 4 and 5, and hard, deep breathing. Plus the mental stress of meeting your target pace.
It's easy to have unrealistic expectations about your target pace from week to week. Usually we set our goal pace based on the best set that we've run in the past 6 months, or maybe our splits from a recent (or not so recent) 5k race. But there are many variables that can influence your intervals pace--sometimes even by as much as 20 to 40 seconds per mile.
- How fresh are your legs? If on the previous day you did intervals on the bike, or did a long brick, you'll be slower than you anticipate.
- What's the course made of? Doing intervals on the same track is the best way to test consistency. But it's boorrr-ing. For more variety, measure out a course on a quiet road, through the park, or on the beach. But recognize that theses surfaces are generally slower than a track. Dirt is slower than asphalt, grass and hard beach sand are slower than dirt. Even different types of tracks are different speeds.
- Is the course completely flat? If you're not on a track, even a barely perceptible grade can slow you down or speed you up.
- Is there a wind? Even a moderate crosswind can make a big difference in pace. A couple of weeks ago I ran intervals back and forth on a straight road during a huge windstorm--so I alternated between a strong headwind and a strong tailwind. My mile pace was a full 50 seconds different!
- Is the course exactly a mile? If you're marking your own course, how exact is it? It takes 4 seconds to run 50 feet--and that's only a 1% measuring error. I have a gps (Garmin 305) to free myself from the tedium of the track--and the margin of error of that is similar.
- What's the air temperature? Did you sleep well last night? Are you hydrated? The list goes on and on...
In short, don't stress about week-to-week pace inconsistencies! Remember, the point of these workouts is to train your body and mind to be more comfortable at race pace.
Yes, your splits should be consistent within a given workout. But otherwise you're mainly getting accustomed to that feeling of discomfort that comes late in the race. Learn what it feels like in your legs and your breathing, and eventually you'll be able to dispense with the watch altogether!
