If you’re familiar with progression runs, the preceding paragraphs may sound familiar. But a “tempo trial,” as the kind of runs mentioned might be called, differs from most people’s idea of a progression run in that it’s harder from the beginning and therefore includes a less steep pace increase throughout the run. Whereas, for example, a four-mile progression run might include miles at marathon pace, half-marathon pace, 10K pace and 5K pace, a tempo trial over the same distance (for a 5K or 10K specialist) might include two miles at threshold pace, one mile at 10K pace and a final mile at as close to 5K pace as you can manage without going overboard and being forced to either slow down or struggle to maintain form to the finish. In other words, for those familiar with competing at 5K or 10K on the track, it should feel like a “tactical” race that goes out slowly and ends up closing with three or four laps that are actually faster than you’d be able to manage in an all-out, evenly paced effort. In any case, your tachometer should only be in the red for the last 15 to 25 percent of the workout.
Former marathon world record holder Khalid Khannouchi is reported to have made use of this basic premise in some of his long runs, in which he closed his final 3200 meters (approximately two miles) on a track at faster than 10K pace. While there is clearly value in inuring yourself against the tendency to slow down in the latter stages of a marathon, be aware that for mortals, these runs are quite taxing and should not be attempted more often that every three weeks or so, and not at all unless you have a genuinely strong endurance base.