80/20 Threshold Booster

Aug 13, 2025

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That Running Guy put out a solid breakdown of slow training and fast racing. Here are the key takeaways so you can try this approach right away.

The 80/20 split: about 80% of your weekly distance easy and aerobic (Zone 2-3), the other 20% as harder work like tempo, threshold, and intervals.
Aerobic running burns fat as fuel, builds aerobic capacity, and lowers injury risk.
Higher-intensity work (the 20%) trains glycogen efficiency, builds pace, and sets up race-day improvements.
For masters runners or anyone with recovery constraints, this ratio is manageable and still produces gains in strength and speed.

Easy runs (80%): a relaxed pace that keeps heart rate in the aerobic zone (Zone 2-3 if you’re tracking). A sample run might be 4 miles at around 8:40/mi, or whatever fits your fitness.
Speed work (20%): try sessions like:
- Tempo or threshold repeats, e.g. 2 × 2 km at just under 5K race speed, with 2-3 min easy jog between.
- Or any tempo/threshold session that feels challenging but doable over 20-30 minutes.

Adjust distances and paces to your training and goals.

Try the 80/20 split for four weeks and see how you feel. The Pacing app lets you set your easy and hard-effort paces to match your targets.

References