How should runners pace during a marathon?

A sound marathon pace balances physiology, psychology, and course conditions. Rather than maximal early speed, most evidence and experienced coaches favor a conservative start, an even middle section, and the possibility of a small increase in effort late if energy allows. This approach reduces the risk of severe glycogen depletion and aligns with how the brain regulates effort during long exercise.

Physiological principles that determine pace

Tim Noakes at the University of Cape Town developed the central governor concept to explain why athletes slow before complete physiologic failure, arguing that the brain continuously adjusts power output to protect homeostasis. Complementing this, Samuele Marcora at the University of Kent proposed the psychobiological model in which perceived exertion and motivation are primary determinants of endurance performance. Both perspectives imply that pacing is not simply about engine capacity; it is a regulated process shaped by feedback about effort, temperature, and fatigue. From a metabolic standpoint, runners who start too fast accelerate carbohydrate use and risk "hitting the wall" later in the race when muscle glycogen is depleted, commonly occurring in the later kilometers. The American College of Sports Medicine advises that endurance athletes plan pacing and fueling strategies together to maintain blood glucose and delay glycogen exhaustion.

Practical pacing strategy

A practical application of these principles is to set a realistic goal pace based on recent long runs and race-specific training, begin slightly slower than goal for the first several kilometers to allow warm-up and traffic adjustments, then settle into even splits for the middle portion of the race. This conservative opening preserves physiological reserves and reduces the likelihood of forced slowdown. Experienced runners often aim for a slight negative split, running the second half equal to or marginally faster than the first, because fatigue accumulates but perceived effort can be managed by earlier restraint. GPS watches and pacing groups help maintain target pace, but should be interpreted alongside on-course conditions.

Contextual and environmental considerations

Course profile, temperature, altitude, and cultural factors such as aid station spacing influence ideal pacing. Hot or humid marathons typically require lower sustained power to avoid overheating; races at altitude demand further conservatism because oxygen availability reduces sustainable speed. Terrain with rolling hills or narrow city streets calls for flexible pacing—temporarily easing effort uphill and recovering on descents rather than rigidly chasing even splits. Local knowledge matters: runners accustomed to a cool, coastal training environment may need to adapt their targets for a hotter race.

Consequences of poor pacing include dramatic slowdowns, increased injury risk from early high mechanical load, and a demoralizing second half. By contrast, a controlled start, steady middle, and opportunistic finish reflect the best current understanding of how physiology and perception interact to produce reliable marathon performances. Practicing race-pace segments, simulating fueling, and adjusting for environmental and territorial specifics will improve the odds that strategy and execution converge on race day.