Marathon Pacing: Choosing a Pace You Can Sustain

The difference between running a pace and sustaining it

A runner may feel comfortable at a particular speed early in a run and struggle to maintain it several hours later. Physiological characteristics such as exercise economy and sustainable intensity can change during prolonged exercise. Durability describes the timing and extent of this deterioration, which is one reason a fresh assessment cannot capture every demand of a marathon. Maunder et al., 2021

Carbohydrate availability also matters. As intensity rises, carbohydrate generally contributes more to energy provision, while prolonged exercise progressively draws on stored glycogen. Hargreaves and Spriet, 2020 An ambitious opening pace therefore has consequences that extend beyond the effort felt during those first kilometres.

The aim is to select a speed that fits the runner’s preparation for the whole event. The opening section should allow the runner to settle into the planned effort, establish the fuelling routine and remain in control. Feeling capable of running faster at that stage is expected; it is not enough evidence to revise the target upwards.

Establishing a target from races and training

A recent 10 km or half-marathon result provides a useful reference because it shows what the runner has performed over a known distance. A marathon prediction derived from that result, however, assumes something about the endurance required to extend the performance. The shorter the race, the more of the marathon remains untested by the result alone.

We interpret race results alongside the training block. Consistent weekly running, the progression of long runs and the response to marathon-effort work all help establish whether the predicted time is plausible. A runner with a strong half-marathon result but an interrupted block should treat the conversion more cautiously than someone whose longer training supports it.

Marathon-specific sessions are useful when the effort is controlled and the runner can repeat comparable work within the wider programme. A single demanding workout completed at the target pace provides less reassurance if it requires several days of disrupted training afterwards. Agreement across several observations provides a firmer basis for the target.

Blood lactate and ventilatory thresholds add information about exercise intensity, but their interpretation depends on the method used. They should not be treated as interchangeable measurements or converted automatically into marathon pace. Jamnick et al., 2020 At DVOTION, we use assessment findings to inform the training zones, then consider the runner’s performances and longer sessions when discussing the race target.

Even pace, positive splits and negative splits

An even split means completing both halves in approximately the same time. A negative split means the second half is faster; a positive split means it is slower. These terms describe how the runner’s speed changes across the race.

A systematic review of 39 studies found positive pacing to be common in marathons, with patterns differing by performance level and other runner characteristics. The findings describe what runners did; they do not establish one compulsory split pattern for everyone. Sha et al., 2024

For a relatively flat course in stable conditions, we recommend a controlled opening followed by a broadly even effort. This gives the runner room to assess the day without deliberately creating a large early time advantage. For a four-hour target, running the first half in 1:58 means averaging about six seconds per kilometre faster than the even-pace schedule. Those two minutes have been gained by increasing the early demand.

A modest negative split can follow when the original target was appropriate and the runner remains strong late in the race. There is no need to force an acceleration simply to achieve that pattern. Equally, some slowing does not prove the entire strategy was wrong: hills, conditions and the runner’s developing fatigue need to be considered alongside the splits.

Translating finish time into running pace

The table gives the average pace required over the official marathon distance. Values are rounded to the nearest second. A sub-four-hour finish requires an average slightly faster than the exact four-hour pace, so rounded watch readings should not be mistaken for a guaranteed finishing time.

Following the plan on the course

Use elapsed time at official distance markers to check the overall schedule. The line a runner takes around bends and through crowds can differ from the measured course, while GPS introduces its own distance variation. The watch remains useful, but repeatedly reacting to instantaneous pace can make the running less controlled.

For a four-hour even-pace schedule, 10 km is reached in approximately 56:53 and halfway in two hours. Checkpoints like these provide a clearer view of progress than a few seconds of fluctuating pace. Rehearse the watch display and lap function during training so checking the plan is straightforward.

Congestion is another reason to remain patient early on. If the first kilometre is slow, settle into the intended effort as space opens rather than repeatedly surging to recover the seconds. With run–walk intervals, the planned average needs to include the walking portions; the pace shown during the running segments will be faster than the overall race average.

Heart rate is supporting information. Use it alongside breathing, perceived effort and the way the pace is developing, with particular caution if the reading is implausible or conditions differ markedly from training. A heart-rate target that encourages the runner to ignore an unusually hard effort is not serving its purpose.

Adjusting pace when conditions change

Environmental conditions affect marathon performance. A large analysis of major-city marathons found air temperature to be an important correlate of finishing performance and withdrawal, with the relationship differing across performance levels. El Helou et al., 2012 A target established in cool training conditions needs reassessment if race day is substantially warmer.

Make that decision early. Begin at an effort appropriate to the day and allow the pace to reflect it. On hills or exposed sections, a rigid demand for identical kilometre splits can also produce uneven effort. The target time remains a reference, while the runner responds to the actual course and conditions.

Fuelling and pacing should remain coordinated. Follow the carbohydrate plan from early in the race and notice whether rising effort coincides with missed intake, stomach discomfort or changing conditions. A late slowdown has several possible contributors; it should not automatically be attributed to a lack of determination or a single missed gel.

As the finish approaches, a runner who remains in control can increase effort gradually. If effort is already rising rapidly, adjusting earlier offers a more manageable decision than repeatedly surging back to a pace that is no longer sustainable. Good pacing brings the original target and the runner’s response on the day into the same decision.