Most marathoners slow down in the second half. The goal of a pacing strategy isn’t to “be brave” early — it’s to arrive at 30–35km with enough energy to keep running well.
Quick definitions
- Even splits: you aim to run the same pace throughout.
- Negative splits: the second half is slightly faster than the first.
- Even effort: you keep effort steady (pace may vary with hills/wind/heat). This is often the smartest real-world approach.
When even splits works best
Even splits can be excellent when the course and conditions make them realistic:
- Flat or gently rolling courses
- Cool, stable weather
- Experienced runners who know their true marathon pace
- Strong fueling habits (so the second half doesn’t become a survival shuffle)
Even splits is simple to execute — but it leaves less margin for error if you misjudge fitness or the day turns tough.
When negative splits is the better bet
For most runners, a slight negative split (or at least a controlled first half) improves your chance of a good result:
- Your first attempt at a goal time
- Crowded starts where it’s easy to get carried away
- Courses with “late-race cost” (bridges, exposed sections, rolling late hills)
- Any day where you’re unsure about weather or pacing
The real advantage: negative-split thinking forces patience early — and patience is what saves your last 12km.
How big should a negative split be?
Keep it realistic. Huge negative splits are rare outside elite racing. A practical target for many runners is:
- Halfway: 30–90 seconds slower than strict even-pace (conservative).
- Second half: equal or up to ~1–3 minutes faster than the first half (only if you’re under control at 30km).
If conditions are hot or hilly, replace “negative split” with even effort and judge success by how well you hold form late.
Even pace vs even effort (the missing concept)
Most real races are not perfectly flat, calm, and cool. That’s why many runners do better thinking in even effort:
- On hills, let pace drift slower uphill and recover naturally downhill.
- Into headwinds, keep effort steady and accept a slower pace.
- In heat, start conservatively and aim to keep form late rather than forcing early pace.
If you keep effort controlled early, you give yourself permission to race late — which is where your time is actually decided.
Decision checklist (2 minutes)
- Hot / windy / hilly? Choose even effort (pace will vary).
- First time at this goal? Lean conservative early.
- Long runs felt controlled late? You can attempt closer to even splits.
- Unsure? Start controlled and “earn” speed after 30km.
A practical pacing plan (that actually works)
- 0–3 km: 2–5 sec/km slower than target while you settle and find space.
- 3–25 km: lock into goal rhythm. Smooth, relaxed, fuel early.
- 25–32 km: protect cadence and posture. Avoid surges. Stay calm.
- 32–42 km: race by effort and form. If you feel strong at 35–37km, squeeze gradually.
Worked example: a “safe” 4:30 plan
If your goal is 4:30:00, your strict checkpoint targets are roughly:
| Checkpoint | Target time |
|---|---|
| 10 km | 1:03:59 |
| Half marathon | 2:15:00 |
| 30 km | 3:11:58 |
| 40 km | 4:15:57 |
A conservative negative-split mindset could mean arriving at halfway 30–60 seconds “behind” those targets — then trying to hold steady effort through 30km before pushing late if you still feel good.
What if you started too fast?
This happens — especially with adrenaline and crowds. The fix is immediate and unemotional:
- Slow down to controlled effort for 2–3 km (don’t “fight” the pace)
- Resume goal rhythm once breathing normalizes
- Fuel and hydrate as planned (don’t skip because you’re “behind”)
Trying to “win back” 30–60 seconds with a surge often costs minutes later.
Fueling: the hidden split strategy
Late slowdowns are often as much about fueling as fitness. A pacing plan that includes consistent fueling is easier to hold:
- Start fueling early (don’t wait until you feel empty).
- Keep effort controlled early so your stomach can absorb.
- If you miss a gel or two, don’t compensate with a surge — get back on schedule calmly.
Use goal pages for exact targets
For exact splits and checkpoint targets, use the calculator and your goal-time pages:
Pacing for a PB vs pacing to finish strong
Your split choice should match your goal:
- Chasing a PB: start controlled, aim for even effort, and only push if you’re still composed after 30km.
- Finishing strong: be more conservative early (slight negative-split mindset), fuel consistently, and protect your legs for the last 12km.
Both approaches reward patience. The difference is how aggressively you’re willing to “spend” effort after 30–35km.
Checkpoint anchors that prevent blow-ups
If you only watch a few numbers, watch these:
- 10 km: relaxed, controlled, breathing easy.
- Half marathon: still smooth; fueling on track.
- 30 km: posture + cadence steady. If you’re straining here, you went too hard early.
Common mistakes that ruin pacing
- Banking time: “I’ll save minutes now” usually becomes “I’m bleeding minutes later”.
- Chasing instant pace: GPS noise causes over-corrections and wasted energy.
- Ignoring conditions: heat and wind require effort-based pacing.
- Racing the first half: your race begins around 30km, not 5km.
FAQ
Is negative split always best?
Not always. On hot, windy, or hilly courses, “even effort” is often better than chasing an exact negative split.
What should my halfway split be?
If you’re pacing conservatively, being 30–90 seconds slower than strict even-pace is common and can set up a stronger finish.
Can beginners run even splits?
It’s possible, but beginners are more likely to benefit from a conservative first half to reduce blow-up risk.
What if I feel amazing at 10km?
Great — keep it controlled. Feeling great at 10km is normal. The goal is to feel “still okay” at 32km.
Should I speed up if I’m behind the pace chart?
Usually no. Return to your planned effort and rhythm. Avoid surges; they’re expensive.
How do I pace hills?
Run even effort: accept a slower pace uphill, and regain gently downhill without spiking effort.
Does fueling affect split strategy?
Yes. Poor fueling increases late-race slowdown. A disciplined first half plus consistent fueling improves your chance of holding pace late.