How Long Should Long Runs Be? (Hint: LONG) - StrengthRunning

Aug 13, 2025

Intro

This is a quick summary of “How Long Should Long Runs Be? (Hint: LONG)” from StrengthRunning. It’s a great watch — we’re breaking it down so you can try the long‑run guidelines today. Be sure to check out the full video for all the details.

Key Points

Long runs are the cornerstone of endurance training – they build mitochondria, reduce late‑run fatigue, and improve overall endurance.
General cap: 20 miles or about 3½ hours, whichever comes first, is the sweet spot for most runners.
Race‑specific guidance:
- 5K/10K: aim for 10‑15 mi long run.
- Half‑marathon: 15‑20 mi (20 mi if you can).
- Marathon: 18‑22 mi (or 3½ h) for most; competitive marathoners may add goal‑pace segments.
If you can’t run long distances (e.g., injury limits you to ~10 mi), supplement with cycling, pool running, or other low‑impact aerobic work to achieve the same time on feet.
Longer is better only when you can keep the time under 3½ h; beyond that, gains diminish and injury risk rises.

Workout Example

Goal	Weekly Long‑Run Distance	Pace Guidance	Optional Add‑On
5K/10K	10‑15 mi	Easy (conversational)	Pair with weekly speed work. See our guides on Mastering 5K Speed and 10K strategies.
Half‑Marathon	15‑20 mi	Easy, finish with 1‑2 mi at race pace if you’re competitive	None or light strides
Marathon (recreational)	18‑22 mi or 3½ h	Easy‑steady; keep HR in Zone 2	For competitive runners: include 3‑5 mi at goal pace. For more on structuring these efforts, see our guide to Mastering Interval Training.
Injury‑limited (10 mi max)	10 mi run or 2‑3 h bike/pool at easy effort	Keep effort easy, focus on time on feet	Cross‑train to add aerobic volume

Closing Note

Give these long‑run guidelines a try this week—adjust the mileage or time to match your current fitness and use the Pacing app to customize the paces. You’ll build the endurance you need and stay injury‑free. Happy running