The Science of Threshold Training

Threshold is the hardest pace you could sustain for about an hour — the line at which lactate production and clearance are exactly balanced. Train it and that line moves up: you can hold faster paces at the same physiological cost. For most amateurs, threshold work delivers more race-time improvement per hour than any other intensity.

What is lactate threshold?

Lactate is not a waste product — it is a fuel your muscles produce constantly and recycle back into energy. At low intensities, the recycling keeps up. At threshold, production starts to outrun clearance and lactate accumulates rapidly. The pace just below that point is your lactate threshold.

How threshold sessions look

• Continuous tempo — 20 to 40 minutes at threshold (RPE 7).
• Cruise intervals — 4 to 6 × 5 minutes at threshold with 1-minute jogs.
• Long threshold — 2 × 20 minutes with 3-minute recovery.

How often

Once a week for almost everyone. Twice a week only in dedicated threshold blocks, with everything else easy.

How to pace it

By heart rate, threshold sits at 85 to 92 percent of max HR. By RPE, 7 — you can speak two or three words at a time, no more. If you can hold a conversation, you are below threshold.