Race-Day Pacing

Even pacing is the plan

Plan to run the second half of the race at close to the pace of the first. Even splits are the standard and they are hard to hold: the unplanned default is a positive split, especially for newer and lower-volume runners. In 78,912 Boston Marathon finishers from 2015 to 2017, the runners who paced evenly finished fastest, a mean of 217 minutes against 276 for those who slowed strongly¹. That shows fast marathoners paced evenly, and not that the pacing made them fast.

For a 4:00 marathon, a 47/53 plan (1:52 then 2:08) is a bad plan. Aim near 49/51, a first half of about 1:57 to 1:58.

Even is a plan and not a law, and patient does not mean timid. In 24 experiments on time trials in cycling, running and swimming, self-selected pacing did no worse than imposed fast-start, even or slow-start strategies, no imposed strategy gave a consistent advantage, and prolonged slow starts went with worse performance. The authors conclude that self-pacing is a flexible strategy that should be matched to the athlete, the environment and the task². So build your plan from your own training and the day, start controlled for the first few miles, and do not give away the first third of the race.

The start

A fast start is a loan you repay with interest. The early miles cost the most, and the crowd will not let you run your pace anyway. In a big, crowded marathon, a runner finishing in 3:45 or slower should start about 20 seconds per mile slow for the first 5K to 10K and pass people in the last 5K. For a 4:00 marathon, a 9:09 pace, that means about 9:30 early and about a minute behind goal at 5K, then easing back toward goal pace so that you are still about 45 seconds behind at mile 20 and become the passer in the last 5K.

In a half marathon the first kilometer runs about 15 seconds per kilometer fast from nerves and the crowd. Stay out of danger, settle within the first couple of kilometers, and run even splits from there.

In big-city races your GPS can be off for the first three to five miles, so you need a benchmark that is not the watch. In training, practice sitting at a 5 or 6 out of 10 effort in a noisy setting, and dial the effort up late.

The middle of the race

Plan a window of 5 to 10 seconds per mile either side of goal pace, and plan to slow 5 to 8 seconds per mile late in the race. Carry a pace band built from the course profile. Take your splits by the clock, because GPS drifts from the mile markers. Expect hills to be slow, and watch the course videos in the final month.

On hills, hold effort steady and let pace vary: ease on the climbs and roll the descents at goal effort. Hold back before hills in the second half. In a half marathon the hardest stretch is 16 to 20 kilometers, and breaking it into single kilometers makes it manageable.

Tuck in behind other runners when you can. It costs less effort than running alone.

Shorter races

A 5K is at pace from the gun. In shorter races you can press earlier than in a marathon, but control over the first third of the race still helps. The shorter the race, the longer the warm-up. See the guide on 5K and 10K training.

Hot days

In heat or at altitude, lower the target for the day and run by effort and not by pace. In the mid-70s F with 85 to 90 percent humidity, add 20 to 30 seconds a mile. Start more conservatively in heat, and adjust your goal before the race, not at mile 18. See the guide on race goal-setting.

What a late slowdown tells you

The size of the slowdown shows what went wrong. Losing minutes a mile at the end, such as 10:00 miles when the goal was 8:00, means you went out too hard. Slowing by 15 to 20 seconds over the last 10K points to leg resilience, which comes from weekly volume and strength work, and to fueling.

Slowing late is common. Among 873,334 Berlin finishers, men slowed 10.7% on average from the first half to the second and women 8.3%, and 17.6% of men and 9.7% of women slowed by 20% or more³. The late slowdown known as the wall has several causes working together: running low on fuel, heat, dehydration, an upset gut, tired muscles and nerves, form breaking down, and pacing errors⁴. Fixing it takes more than a carbohydrate load: a start you can hold, fuel from early, hot days run by effort, and legs built by weekly volume.

If the last 10 miles go wrong and you cramp or cannot take fuel in, alternate 5 minutes at marathon effort with 5 minutes easy to stop the bleeding.

Related guides

For fueling the plan, see race-day fueling and carbohydrate during exercise. For the weeks before the race, see race-specific preparation. For marathon training as a whole, see marathon training.