How it works
The aim is to spend a lot of time right at the edge where lactate starts to accumulate (LT2), without tipping over it. Held under control, this intensity drives strong aerobic adaptations while keeping the session repeatable rather than exhausting. The key word is controlled: stay just below the line, don't race it.
The Norwegian double-threshold twist
Pioneered by Marius Bakken and later popularized by Jakob Ingebrigtsen and the Norwegian triathletes, the method runs two sub-threshold sessions in the same day (for example morning and evening). Blood lactate is measured between intervals to keep each rep slightly below LT2, so the athlete accumulates a very high weekly volume of quality work without the wreckage of one all-out session.
How to apply it
Most amateurs can't do this literally: it depends on a lactate meter and the time and recovery for big volume. Borrow the principle instead. Run threshold intervals at a pace or heart rate you could just barely sustain for an hour, stay disciplined about not pushing harder, and keep the rest of your week genuinely easy. Controlled threshold plus mostly easy mileage captures most of the benefit.
FAQ
What is the lactate threshold (LT2)?
LT2 is the intensity above which blood lactate rises faster than your body can clear it. In practice it sits close to the hardest steady effort you could hold for about an hour, and it's the anchor point for threshold training.
Do I need a lactate meter to train this way?
To follow the Norwegian method literally, yes, because the whole point is keeping each rep precisely below LT2. Without one, approximate the same zone with heart rate or pace, aiming for a controlled effort that feels comfortably hard rather than maximal.
Is double-threshold training right for beginners?
Generally no. Two quality sessions in a day demand high fitness, careful fueling, and real recovery time. A beginner gains more from one controlled threshold session per week plus easy aerobic running, the safe way to borrow the idea.