RunPackGuides · 5 min read
Negative splits: how to run the second half faster
What a negative split is, why it’s the best way to race 5K to marathon, how to plan one with checkpoint times, and a simple workout to practise it with friends.
A negative split means running the second half of a run or race faster than the first. An even split is both halves at the same pace; a positive split is slowing down. Most people run positive splits without meaning to: the start feels easy, adrenaline does the rest, and the last third hurts.
Why it works
Going out a little too fast costs more time later than it saves early, because the effort catches up with you. Holding back slightly at the start keeps something in reserve, and passing people in the final kilometres feels a lot better than being passed. Many of the fastest long-distance races are run with even or slightly negative splits.
How to plan one
- Pick a realistic goal time from a recent race. The pace calculator predicts one from another distance.
- Work out your even pace for that time, then plan the first half a few seconds per kilometre slower and the second half a few seconds faster. For a 2:00 half marathon (5:41 /km), that might be 5:45 for the first 10 km and 5:37 after.
- Write down two or three checkpoint times. The half marathon and marathon pace charts list them.
- Ignore the crowd for the first kilometre. It’s the one most people get wrong.
A workout to practise it
The progression run: run the first third easy, the middle third at a steady effort, and the last third at a comfortably hard pace. For example, 2 km easy, 2 km steady, 2 km a little quicker. It teaches you what holding back feels like.
With friends, run the first two-thirds together at the slowest person’s easy pace, then let everyone pick it up for the last part at their own speed and regroup at the end. Everyone gets their own workout, and nobody runs alone.
Checking your splits afterwards
Most running apps show a split for every kilometre or mile. Compare the first half with the second: within a few seconds is an even split; quicker at the end is a negative one. Over a few races you’ll learn how fast you can safely start.