Race-Day Pacing — Don't Go Out Too Fast

Even and negative splits win

On flat courses, distributing your effort evenly (or finishing slightly faster than you started) produces the best results across endurance events¹. The opposite — positive splitting, going out fast and fading — is by far the most common pattern: a systematic review of marathon studies found runners started too fast in roughly 77% of cases, and ran true negative splits only ~18% of the time². Banking time early almost never pays; it borrows against a much larger late-race tax.

Why fast starts backfire

Start too hard and you burn through stored carbohydrate faster and tip into a less efficient effort — which in the marathon shows up as "the wall," the dramatic slowdown after ~20 miles. A four-million-record analysis found a large share of marathoners hit it, with risk highest when runners take pacing risks chasing a personal best³. Conservative early pacing is the cheapest insurance against a blow-up there is.

How to pace it

Pace by effort, especially when conditions or terrain vary:

• The first portion should feel almost too easy. If goal pace feels hard early, it's the wrong goal pace for the day.
• On hills, hold effort steady rather than pace — ease on the climbs, roll the descents at goal effort (don't hammer them and trash your quads).
• In heat or at altitude, adjust your target down; your watch's pace plan assumes neither.
• The shorter the race, the more you can press early — but even 5K and 10K reward control over the first third.