How can sprinting complement distance running?
What if distance running is just a conservative sprint, and efficient sprint mechanics carry over into distance running? Then to optimize mechanics for distance running, you should optimize mechanics for sprinting. It also follows from this idea that without sprint mechanics, the mechanics of distance running may not be optimized. Running mechanics of top sprinters do not vary that much while the mechanics of distance runners vary more widely. The most obvious mechanical variation in distance runners is the relative position of the trailing knee and lead foot at ground contact. The varied mechanics of distance runners suggests that inefficient mechanics may not prevent high levels of performance, but that there is an opportunity to improve the mechanics and improve performance.
If someone has always been a distance runner, and has never developed sprint technique, they may be missing some of the components that could benefit their distance running. A mechanical inefficiency while sprinting 100 m. or 200 m. may be more apparent in time compared to a similar inefficiency while running 1 or more miles. The shorter distances can give more feedback to the runner as the mechanics are refined, and more trials can be taken in one workout. The shorter sprints also require more complete connections between the mechanical components. If one component is passive in a 100 m. the result is more apparent than during a longer run where the passive component has less of an impact on speed and may be more difficult to identify.