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Two pacing myths I wish someone had killed for me earlier

5 min read #running #pacing #marathon

I spent the first three years of running believing two things that turn out to be wrong. Both are common enough that ~half the runners I meet at race finishes still hold them. Killing each one is worth a few minutes off your next race.

Myth 1: “Even splits are the optimal pacing strategy”

The intuition is sensible: if you have X minutes of glycogen and Y miles to cover, a constant pace minimises fatigue. So even splits = best result. Right?

Actually no. Negative splits — running the second half faster than the first — produce faster overall times for nearly every runner over distances longer than 5K. The data is consistent across major marathons: the top 10 finishers almost always run negative splits. The amateurs in the back half almost always run positive splits (slowing down).

Why?

  1. You start faster than you think. Adrenaline at the gun, nervous energy, fresh legs all push you a few seconds per km faster than your “feels like” pace. By km 8 you’re paying for it.
  2. Glycogen burns in the first 90 minutes, then the body switches to fat oxidation. Running too hard early uses glycogen unnecessarily and leaves you hitting the wall at km 30.
  3. Mental gain. Passing people in the second half is energising. Being passed in the second half is demoralising. The mental side compounds the physical side.

The fix: target the first 20–30% of the race at 5–10 sec/km slower than your goal average. Make up for it in the back half.

For a 4:30/km marathon target, run the first 10K at 4:35–4:40, the middle 22K at 4:30, the last 10K at 4:20–4:25. Net average lands at 4:28–4:30, and you finish strong instead of crawling.

The pace calculator’s splits table is for reference only — it shows even splits. Your race plan should not be even splits.

Myth 2: “Long-run pace = marathon goal pace minus 30 sec/km”

This rule is taught in many beginner training plans. It’s not wrong, but it leads to two specific failure modes I keep watching unfold:

Failure mode 1: long runs become marathon-pace runs

A runner targeting 4:30/km marathon does 30 km long runs at 4:50/km. By race day they’ve done six 30K efforts at 4:50/km. Their body is trained to comfortably hold 4:50/km. They line up to run 4:30/km — a significantly different physiological demand they’ve never simulated — and slow down dramatically after km 25.

Fix: the “long-run pace” should be 60–90 sec/km slower than marathon goal pace, not 30. Long runs build base aerobic capacity and capillary density. They’re not race-pace simulations. Save race-pace effort for specific tempo runs and the marathon-pace segments inside long runs.

Failure mode 2: long runs done too fast cost recovery time

A 30 km long run at 4:50/km is a 2:25 effort that takes 3–4 days to recover from. The same 30 km at 5:30/km is a 2:45 effort that recovers in 1–2 days, leaving you actually able to do the next hard workout in the week. Slower long runs let you train more total volume.

Fix: treat long runs as endurance volume, not “the easier version of race pace.” Most pros run their long runs at 65–75% of marathon pace by heart rate.

What to actually use the pace calculator for

These myths are about training paces, where the calculator can’t help you (it doesn’t know your physiology). What the calculator is great for:

  1. Race-day plans. Type in your goal time, see the splits, then mentally add 5 sec to the first quarter and subtract 5 sec from the last quarter.
  2. “What time is X pace × Y distance?” Stop doing this in your head on the run. Easier to check before.
  3. “What’s a Riegel-realistic time for my race?” Fast sanity check before setting an audacious goal that will end in a wall at km 30.

The math is the easy part. The art is deciding what target time to plug in. Negative splits, slower long runs, and not chasing the hero session that costs you the rest of the week — those are the real wins.