Do you incorporate speed work into your training schedule?

First off, it is important to specify what people mean when they talk about "speed work." In training, speed work usually refers to interval training at your VO2 max rate -- "the highest rate of oxygen consumption attainable during maximal or exhaustive exercise." The higher your VO2 max, the more oxygen your muscles can process during exercise. VO2 max is closely tied to genetics, but speed work -- particularly interval training -- can increase it.

Runners also use a term known as a "tempo run." Tempo runs refer to running for periods of time at a rate just below the "lactate threshold" pace. What the heck is this dog talking about? Your lactate threshold is the point at which the body's ability to clear lactate, the by-product of metabolism, can't keep up with lactate production. Generally, the lactate threshold is about your race pace. Tempo runs, then, are runs that incorporate periods where you run just below your race pace. Experts generalize by calling it "comfortably hard." For those of you with the ability to talk, just below your lactate threshold would be running at a rate where you can say a few words ("where's the dog?"), but you couldn't have a lengthy conversation. ("Right over there.") Tempo runs vary based on the length of the event you're training for, but they comprise of an easy warm-up, a period of time running just below the lactate threshold rate, a brief rest (running slowly or walking), another stretch of "comfortably hard," and a warm-down.

Back to your question, yes, I incorporate speed. I do interval training at the dog park and when I see wildlife. I don't usually do tempo runs; for me and my running partners, their tempo pace is my LSD -- long slow distance. I don't mind, though. They're working on it, and -- through training -- they can increase both their VO2 max rates and their lactate thresholds.