Health · 4 min read
Negative Splits: How to Pace a Race Properly
A negative split means running the second half of a race faster than the first. An even split means running both halves at about the same pace. For almost everyone, either of those beats the most common race strategy, which is going out too fast, feeling great for 20 minutes, and then slowing down painfully for the rest.
Why starting fast costs you
At the start you're rested, full of adrenaline and surrounded by people moving quickly. Running 10 seconds per km faster than your goal feels easy. The problem is that effort doesn't stay linear. Going faster than your sustainable pace early burns through energy stores and builds fatigue that you can't fully recover from while still racing. The seconds you "banked" early are usually repaid with interest later.
It's often noted that many distance-running world records have been set with even or slightly negative splits. That's not a coincidence.
What a negative split looks like
10K, goal 50:00 (5:00 per km average):
- First 5 km: about 25:15 (5:03 per km)
- Second 5 km: about 24:45 (4:57 per km)
That's only a few seconds per kilometre difference. A negative split doesn't mean jogging the first half; it means starting controlled.
Half marathon, goal 2:00:00 (5:41 per km average):
- km 1–5: 5:45–5:50, deliberately easy while the crowd settles
- km 6–15: 5:40 per km, locked in
- km 16–21: 5:35 or faster if you feel good
Use the pace calculator to get your average goal pace and splits for any distance.
The marathon is special
For the marathon, a true negative split is hard for most recreational runners, because fatigue builds so much in the last 10 km. A more realistic target is even pacing, or a second half no more than a couple of minutes slower than the first. The key rule is the same: the first 10 km should feel almost too easy. If you haven't settled on a goal yet, see how to pick a realistic marathon goal time.
How to actually do it on race day
- Write your splits down. A few key checkpoint times on your hand or phone lock screen help you ignore the crowd.
- Start near runners of your speed. Starting too far forward drags you into someone else's pace.
- Watch the first kilometre. If it's more than 5–10 seconds faster than plan, ease off immediately. It's the easiest correction you'll make all day.
- Use effort, not just pace, on hills and in wind. Hold steady effort uphill and let the pace come back on the descent.
- Heat changes the plan. On a warm day, start slower still and accept a slower time. Heart rate is a useful guide; see heart rate zones explained.
Practise it in training
Progression runs are the easiest way to learn negative splitting: start easy and finish at a steady, strong effort. For example, a 40-minute run with the last 10 minutes at about half-marathon effort. Over time, your body learns what "controlled" feels like at the start, and your brain learns to trust that you'll have something left at the end.
The payoff
Besides usually running faster overall, negative splitting feels far better. Passing people in the last few kilometres instead of being passed is a much nicer way to finish a race, and it's the kind of race that makes you want to sign up for the next one.
Frequently asked questions
What is a negative split in running?
Running the second half of a race faster than the first half.
Is it better to run even or negative splits?
Both are better than a fast start followed by a big slowdown. Negative splits suit shorter races; even pacing is a realistic target for most marathon runners.
How much faster should the second half be?
Only slightly. For a 10K, a few seconds per kilometre faster is plenty. The main goal is to avoid starting too fast.
How do I stop starting a race too fast?
Write down target splits, start near runners of your pace, and slow down immediately if your first kilometre is well ahead of plan.