What it is
A threshold run (also called a tempo run) is a sustained effort at or just below the lactate threshold — the pace at which lactate accumulates faster than it can be cleared. Classically described as "comfortably hard": you can speak in short phrases, but not hold a full conversation.
Threshold pace sits roughly at 10K to half-marathon race pace for most trained runners.
How to run it
- —Pace: Lactate threshold pace — typically 20–30 seconds per kilometre faster than marathon goal pace, or roughly 85–90% of maximum heart rate.
- —Classic format: 20–40 minutes continuous at threshold pace, bookended by 10–15 minutes easy warm-up and cool-down.
- —Cruise intervals variant: 3–4 × 8–10 minutes at threshold with 60–90 second recovery jogs. Allows more total threshold volume with slightly less mental demand. Useful early in a training cycle.
- —Feel: Sustainable but not comfortable. You should be working but in control. If you're gasping, you've gone over threshold.
The adaptation
The threshold run is the most direct tool for raising the lactate threshold:
- —Lactate clearance — sustained effort near threshold trains the body to clear lactate (via oxidation in the heart and slow-twitch fibres) as fast as it produces it. Over time, the threshold pace rises.
- —Running economy — regular threshold work improves neuromuscular efficiency at goal pace: the same speed requires less oxygen and less metabolic cost.
- —Mitochondrial quality — threshold pace creates a strong aerobic stimulus without the tissue damage of faster intervals. High-quality mitochondria process lactate efficiently.
- —Psychological threshold — regular time at "comfortably hard" desensitises the discomfort of sustained effort, which matters enormously at marathon pace for 3+ hours.
When to use it
- —Once per week as a key session, typically mid-week.
- —Early and throughout the marathon cycle — threshold is never "done".
- —When building volume before introducing VO₂ work. Threshold first, then sharpening.
When not to use it
- —Don't add threshold on top of a heavy interval week — the two sessions target different systems but share recovery cost.
- —Avoid running threshold at "what I think is threshold" without checking heart rate or pace. Most runners go too fast and turn a threshold run into a moderately-hard slog that taxes neither system optimally.
- —Skip in weeks with high accumulated fatigue. A tempo on tired legs drifts above threshold and becomes high-intensity without the intended stimulus.