August 27, 2025
Double threshold training has captivated the running world, thanks to the remarkable achievements of Norwegian athletes like the Ingebrigtsen brothers. But how does this system really work, and why has it gained such a following? Below, we’ll introduce the fundamental ideas behind double threshold training and explore how it caught fire among both elites and recreational runners.
Double threshold training involves doing two workouts in one day at just below your lactate threshold, often referred to as “tempo” or “threshold” pace. Lactate threshold pace feels “comfortably hard”—it’s challenging but not an all-out sprint. By splitting this threshold workload into a morning and an afternoon session, runners can accumulate more total time at a highly effective aerobic intensity without overwhelming fatigue. For example, instead of cramming a big block of, say, 6 × 10 minutes at threshold into one session, you might do 3 × 10 minutes in the morning and 3 × 10 minutes in the evening.
Proponents argue that splitting a single threshold workout into two allows you to maintain better form and stay more solidly in your aerobic “sweet spot”. Physiologically, threshold training develops your capacity to clear lactate and sustain faster paces comfortably. Over weeks and months, this can translate into better stamina, higher sustainable speeds, and improved race performances. It’s no wonder the method gained popularity once runners saw the huge success of Norwegian track stars—who rely heavily on this “two-a-day threshold” routine.
While the concept of two hard sessions in one day isn’t entirely new—coaches like Renato Canova and Sebastian Coe have used variations for decades —Norwegian athletes brought unprecedented structure to it. Olympian Marius Bakken conducted thousands of lactate tests on himself to refine a system of threshold-focused doubles that helped him run a national-record 13:06 for 5K. Later, the Ingebrigtsen brothers adopted a similar approach, routinely performing threshold workouts twice a day with precise intensity control.
Jakob Ingebrigtsen’s Olympic gold and multiple world records accelerated the buzz. Coaches and commentators noted how he and his brothers spent a huge portion of their weekly mileage at or near threshold, yet often recovered quickly to train again the next day. Observers credited disciplined pacing—never going above true threshold—and plenty of easy running on non-workout days. Seeing world-class domination rooted in these methods has convinced many runners to try it themselves.
Threshold training has long been touted as one of the best ways to improve aerobic fitness. Running at just below your lactate threshold enhances your ability to clear lactate, boosting the speed you can hold before fatigue sets in. By splitting one monster threshold workout into two smaller sessions, you accumulate more total time at this key intensity across the week, potentially with less acute stress on the body.
One study compared runners who did all their threshold work in a single session versus those who split the same total volume into two sessions separated by a few hours. The double-session group generally felt less battered afterward and showed lower markers of fatigue. This implies you can pack in a fair bit of threshold running if you distribute it intelligently. The challenge, of course, is staying disciplined so both sessions remain truly sub-threshold rather than drifting into an all-out effort.
Despite the allure, double threshold training is not risk-free. Two hard sessions in the same day substantially raise your training load. If you’re not cautious with pacing and recovery—especially for amateur runners juggling jobs and family life—you can slide into overtraining or injury. Think of it as an advanced tool: it can unlock new levels of fitness, but only if you have a solid base, manage volume carefully, and keep the intensity in check.
In the next installment (Part 2), we’ll dive into how amateur runners can adapt the Norwegian double threshold concept to their own training. You’ll see why “comfortably hard” is the magic phrase—and why you should start with smaller bites of threshold volume, not a full-on pro schedule.
