Issue #21: Double Threshold Training

✍️ Author’s Note

Welcome back to The Threshold Lab! I’m Stephen Pelkofer, an aspiring HYROX Elite 15 athlete and research/data nerd. Each week I choose a training topic, dig into the research, and translate it into practical strategies. This week we are going back to some of the inspiration for starting this newsletter and my coaching business → Double Threshold Training 😁

🥞 Fueling for Performance

If you’ve been reading this newsletter for a bit or you follow me on Instagram, you know that I’m on a high carb craze right now. Here’s is how I’m fueling my double threshold sessions:

• Before and during training → 2.5 scoops of 1st Phorm Ultra-Formance (60g of carbs total)

• After training → 1 scoop of 1st Phorm Ignition (43g of carbs) and 1.5 scoops of Phormula-1 Clear Whey Protein (33g of protein).

This stack is allowing me to (1) train harder for longer durations and (2) recover better for the next session. Have questions about other 1st Phorm products? Reply to this email and I’ll help you out.

👨‍💻 Introduction

Topic: Double‑Threshold Training – A Practical Guide

OG Threshold Lab members might remember Issue #1 of this newsletter, which was devoted entirely to lactate threshold and threshold training. In this issue, we dive into a training model that has become popular over the past few years in endurance sports – double‑threshold training.

Popularized by Norwegian middle‑distance runners and triathletes, this approach stacks two moderately hard sessions in the same day. Athletes control the intensity by measuring blood‑lactate concentration during the workouts. Their success has attracted attention from coaches across disciplines.

This discussion centers on the work of Marius Bakken, whom many consider a pioneer of the double‑threshold approach. Bakken was a Norwegian middle‑distance runner in the 1990s and early 2000s with a 5 km best of 13:06. Through meticulous experimentation and thousands of lactate readings, he shaped the method that is widely used today.

🔍️ Deep Dive

What is Lactate Threshold?

There are generally two thresholds that coaches and athletes refer to:

• Lactate Threshold 1 (LT1) – the point where blood‑lactate concentration first rises above resting levels. At slow speeds, lactate production and clearance are balanced, so concentration remains low. As intensity increases, there is a gradual rise; this marks LT1.
  

• Lactate Threshold 2 (LT2) – a higher intensity where blood‑lactate levels climb rapidly. Once you cross LT2, the effort becomes increasingly unsustainable, and you must slow down or stop.

What Is Double‑Threshold Training?

“Double threshold” refers to performing two separate threshold workouts on the same day, typically at least six hours apart. Each workout is composed of repeated intervals at an intensity that yields blood‑lactate concentrations of roughly 2–4.5 mmol, measured between intervals with a portable lactate meter Monitoring lactate helps athletes stay near their threshold rather than relying solely on pace or power.

Double‑threshold days are usually part of a hard‑day/easy‑day structure: two threshold clusters and one high‑intensity session constitute the hard days, and the rest of the week consists of easy runs or low‑intensity sessions. This organization emphasizes internal load (lactate) rather than external metrics (pace, power), allowing athletes to train near LT2 without accumulating excessive fatigue.

The Bakken Model

A typical double‑threshold day in Marius Bakken’s model looks like this:

• Session 1 (morning): longer repetitions at the lower end of the threshold range, such as 5x6min at ~2.5–3.0 mmol
  

• Session 2 (afternoon): shorter, slightly faster repetitions at the upper end of the threshold range, such as 20x400m at ~3.5–4.0 mmol

Bakken found that blocking sessions in this way reduced muscular stiffness between sets and enabled him to accumulate more total time at threshold than if he performed one long session. A typical training week in his model comprises:

• Two double‑threshold days

• High volumes of easy training – threshold days are always followed by at least one easy day

• One “X‑element” session – a workout above LT2 focusing on VO₂ max or sprint ability (a key ingredient to keeping the top end sharp!)

Why This Works

The goal of threshold training is to spend time at intensities around LT2, where lactate production and clearance are balanced and aerobic metabolism is maximally stressed without runaway fatigue. Long threshold sessions can lead to upward drift in heart rate and lactate, reducing mechanical efficiency and extending recovery. Splitting the work into two shorter sessions reduces internal stress. A 2024 study compared a single 6x10min interval session with two 3x10min min sessions separated by 6.5 hours; the single session produced larger increases in heart rate, lactate and perceived exertion, and participants reported greater fatigue and muscle soreness the next day (study link). When the same volume was split into two sessions, heart rate and lactate were lower during the second session and recovery was faster. This suggests that spreading threshold work therefore improves quality and may allow higher weekly volumes without excessive strain.

🧪 Lab Notes

Most (nearly all) of us are not elite athletes – we don’t need to be pricking our fingers after every interval to get a blood lactate reading, but that doesn’t mean we can’t benefit from this style of training. Here are some of my thoughts after trying out versions of double threshold on myself for the last 18 months:

• First → Re-read Issue #1, where I talk about some easier ways to understand where your estimated threshold pace might be.

• Stacking two moderately hard sessions in the same day is a great way to get more volume at a faster pace.

  • A lot of new runners listen to the online zone 2 lords and think they’re going to get fast by doing a bunch of easy work – I have personally found this to not work very well (and most credible research would agree).

  • Threshold work is a good middle ground between doing easy work and really fast interval work.

  • Work around LT2 is phenomenal for building your engine – if you can stack consistent threshold work for 16 straight weeks, I’m pretty certain that you would take time off of any run distance PR below the half marathon distance.

• Start small and work your way up to more volume

  • Beginner: Complete two threshold sessions a week (Tuesday-Friday for example)

  • Intermediate: Change one of the days to a double session, but the second session is on the bike/skierg/rower (a lot of HYROX elites are training this way)

  • Advanced: Switch one day per week to a double threshold running day – longer intervals in the morning and shorter, faster, intervals in the evening

• Timing/Periodization thoughts

  • I personally think double threshold running is great for a base building phase.

  • For HYROX competitors, I think focusing on big threshold sessions becomes more important when it is close to race day.

• As always, fuel for your sessions and prioritize recovery

  • As training volume and intensity increases, carb intake becomes even more important

  • Don’t forget about the most important recovery tool of them all → consistent sleep

That’s it for this edition of the Threshold Lab! Are there any training topics you want to learn about? Reply to this email and let me know!

🔗 References

• Marius Bakken, The Norwegian Model

• Marius Bakken, Norwegian Model Revisited

• Kjøsen Talsnes R, Torvik PØ, Skovereng K, Sandbakk Ø. Comparison of acute physiological responses between one long and two short sessions of moderate-intensity training in endurance athletes. Front Physiol. 2024 Jul 30;15:1428536. doi: 10.3389/fphys.2024.1428536. PMID: 39139482; PMCID: PMC11319183.