The 800 m
Note
This page is a synthesis; the individual claims are graded on the pages they link to. The energy-system split of the 800 m is well measured and the qualities that separate good 800 m runners are reasonably well profiled, but how best to train for it rests more on coaching practice than on head-to-head trials, so the prescription below is descriptive rather than proven.
The 800 m sits at the edge of distance running. Two laps take competitive runners between roughly two and two and a half minutes, long enough that the aerobic system already does most of the work: treadmill simulations put the aerobic share at about 66% (Spencer & Gastin 2001). That still leaves a third of the energy coming from anaerobic sources, by far the largest anaerobic fraction of any event in this wiki, which is why the 800 m trains and races more like a long sprint than a short distance race.
What decides it
The binding qualities are anaerobic capacity and the anaerobic speed reserve: the energy a runner can supply without oxygen, and the gap between maximal aerobic speed and flat-out sprint speed. The 800 m is run above the velocity that elicits VO₂max, inside that reserve band, so the size of the band shapes the race. Among the world’s best 800 m men, sprint speed and speed reserve sorted athletes into a speed-based type and an endurance-based type, two routes to the same time (Sandford et al. 2019). The runner with more top-end speed sits at a lower fraction of maximum for any given pace, which leaves room for a kick.
Training approach
The base is shared with every other distance: a foundation of easy aerobic volume, on top of which the event-specific work is layered (Haugen et al. 2022). What differs is how much of the sharp end is anaerobic. The 800 m sits at the polarised end of the distance-specific continuum, pairing that easy base with a high dose of very hard work (Casado et al. 2022): repeat efforts at and faster than race pace to build specific endurance, VO₂max intervals to lift the aerobic ceiling, and short, fast strides and speed work to raise the top speed that race pace sits beneath. Buffering aids earn their keep here in a way they never do over the marathon: sodium bicarbonate and beta-alanine help exactly the acidosis-limited efforts of one to a few minutes the 800 m is made of (Baker et al. 2010).
Racing it
The first lap is almost always faster than the second, partly an unavoidable artefact of accelerating from the gun and of positioning, partly because top speed cannot be held once lactate climbs (Abbiss & Laursen 2008). Fuel is a non-issue: the race is over long before glycogen matters, so there is nothing to eat or drink and nothing to load. The skill is committing early and holding form as the second lap bites. See race pacing.