Moving up from striders and pick-ups, the next main type of faster running is bursts of 60 to 90 seconds at what feels like the pace you could run for a mile. The point of these are to improve your running economy, or how efficient you are (in terms of oxygen consumption) at a given speed. Targeted efforts at this effort level will make you more efficient at all speeds.
Traditionally, this workout is done by doing one-lap repeats of a standard 400-meter track. But there’s nothing magical about the distance of 400 meters; it’s simply convenient to do one-lap repeats. The important thing here is the amount of time, 60 to 90 seconds, at that intensity of roughly mile race pace. A standard running economy workout would total between 2 and 3 miles worth of hard running, such as ten 400-meter repeats or twelve 300-meter repeats.
These repeats quickly become taxing. So that you can do them all at the right intensity level, you’ll need a good recovery jog between. A convenient parameter is to jog for the same distance as your hard bouts. If you’re doing the workout based on time, do recovery jogs that last 50 percent to 100 percent as long as your fast runs; for example, 80 seconds hard followed by a 2-minute jog.