Issue #13: Speed Endurance Training

✍️ Author’s Note

Welcome to Threshold Lab, where each week I break down one training topic, dig into the science, and give you actionable protocols to use immediately. I’m Stephen Pelkofer, an aspiring HYROX Elite 15 athlete with a men’s pro personal best of 59:41 and men’s pro doubles best of 51:39. Let me read the research, listen to the experts, and then give you the tools to make it work for you.

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👨‍💻 Introduction

Topic: Speed Endurance Training (SET)

Endurance athletes often have an obsession with volume. More volume = better results. In a lot of cases this is probably true, and the more volume you can handle over time, the better your performance will be. However, there is a growing body of research focusing on increasing intensity and reducing volume, and what that does for performance gains in events from 10s in duration all the way up to 60+ minutes.

We’ll focus on one specific area of this research in today’s issue: Speed Endurance Training (SET) - implementing very intense but short intervals into your training routine. Recent analysis by researchers pulled together studies on trained runners, cyclists, and team sport athletes to see what happens when they add these “supramaximal” bursts to training. The headline: athletes got faster across the board, even when cutting back their total training volume significantly. And here’s the kicker: these gains even showed up in elite-level athletes who usually struggle to squeeze out significant performance gains.

The meta-analysis we will go over today is from this paper: Speed Endurance Training to Improve Performance (Jens Bangsbo, Julie Kissow, Morten Hostrup)

⚡ Fast Finds for the busy reader

• 30-20-10 intervals: A simple formula of 30 seconds easy-20 seconds moderate-10 seconds fast, repeated in 5-minute blocks, has been shown to dramatically improve running performance even with fewer miles of training.
  

• High-intensity, low-volume: SET is very time-efficient. Studies saw performance improve even when total training volume was slashed by 30–60% as athletes substituted easy miles for speed work.
  

• Increases in Exercise Economy: The magic of SET is largely in making you more efficient. Athletes significantly improved their running/cycling economy (using less energy or oxygen at a given pace) after adding speed workouts.

🔬 Deep Dive

What exactly is Speed Endurance Training? SET refers to interval training done at intensities above the power/pace that elicits your VO₂max. These are near-max-effort bursts, but not all out sprints. Classic SET workouts range from ~10 seconds up to 1-2 minutes of work. Researchers further classify them into “production” vs. “maintenance” sessions. SET-P (production) workouts focus on short (10-30s) efforts with full recovery, aiming for peak power output on each rep. Think 30 seconds hard, then 3 minutes rest, repeated a handful of times. In contrast, SET-M (maintenance) involves longer intervals (say 1-2 min) or shorter rests to induce fatigue and stress your ability to sustain high intensity. An example would be 5x1 minute fast with only 1 minute rest, which forces you to hang on as lactate builds up. The key point: “speed endurance” isn’t about top sprinting speed, it’s about your capacity to repeatedly produce high power despite fatigue.

How can near-max efforts improve endurance performance? At first glance, it seems weird: if you’re training for a 10K or a HYROX race (which takes > 60min), how do 30-second bursts help you besides maybe improving your top speed? The answer lies in a mix of central adaptations and muscular adaptations that these efforts provoke. The meta-analysis highlights that, in trained athletes, SET enhanced performance without changing VO₂max, primarily by improving “exercise economy” and the ability to handle byproducts of intense exercise. Running economy is essentially how much oxygen you need to run at a given pace – if you improve it, you can run faster for the same effort. The economy improvement stems from neuromuscular adaptations: speed work reinforces efficient form (you learn to generate more force per stride) and recruits fast-twitch muscle fibers, which over time can make submaximal paces feel easier. Speed work also increases muscle enzymes and transport proteins that help with anaerobic energy production and pH regulation. These changes mean you can tolerate and recover from high-intensity bursts better (useful even in an endurance race that might feature hills or surges).

Performance results, even with less training: The real-world outcomes of adding SET are impressive. Across events from ~1 minute up to an hour, athletes who introduced a few weekly speed work sessions saw measurable improvement. Many of these studies had athletes swap out a chunk of their normal training volume for the speed work, rather than piling it on top of an already heavy load. For example, one group of runners cut their weekly mileage by 30% when they started doing 2-3 SET workouts (30-second hill sprints) plus one 4x4 min interval workout per week. After ~7 weeks, their 10K times dropped by about 60 seconds, despite less total running (a strong example of the quality-over-quantity idea). 

In a study on elite cyclists (average VO₂max of ~71… very high), just a single weekly SET session (twelve 30-second bike sprints) combined with two moderate intensity sessions (4-minute intervals) for 7 weeks led to a ~2-3% improvement in 20-minute time trial performance – this is an insane improvement for an athlete at this level. Even more interesting, the researchers ran two versions of that experiment: one group maintained their usual volume and just added the intensity, while another group reduced their training volume by one-third when adding the SET and intervals. Both groups improved equally. So one group got the same benefit as those who kept their normal training load. While this wasn’t the focus of the research, I think this data supports the idea of reducing volume but increasing intensity during pre-competition tapers – I’ll cover this in a future issue when I’m setting up my taper for an A-race.

Time for some lab notes ⬇️

🧪 Lab Notes

In every issue of this newsletter, the “Lab Notes” are going to be the protocols that you can apply to your training and routine right away. The goal of this section is to translate the science into actionable steps for the reader, whether you’re a recreational runner/HYROX competitor, or someone pushing the limits of their peak potential.

• A quick reality check before the fun tips: SET workouts are low-volume, but they can still be very intense, and with intensity comes the need for caution. Keep the volume of speed work low early on and ensure adequate recovery between sessions. And make sure you are warmed up before you start opening up that stride!
  

• Ease into SET with strides or 30-20-10 workouts: Start by adding strides at the end of easy runs 1-2 times per week. For example, on two of your weekly easy days, finish with 4-6x20-second fast strides (around your estimated 1-mile pace) with full walking recoveries. These act as a micro-dose of SET → sharpening your speed and form with minimal fatigue. As you get comfortable, try a 30-20-10 session. Example: 10 min warm-up jog, then 3 sets of 5 minutes of 30-20-10 intervals (30s easy, 20s moderate, 10s fast, repeating continuously), with 2 min easy jog between sets.
  

• Swap out volume for intensity: This is especially important for new runners. You need to get better at running, but that doesn’t mean you should just go run a bunch of easy slow miles trying to keep your heart rate low. Small and frequent doses of intensity and speed will give you the adaptations needed to become faster. Building a base doesn’t just mean training the slow end. The 80/20 (easy/hard) split is way more applicable for an elite athlete training 15+ hours a week – I will dig into this research many more times in future issues.
  

• Apply SET to HYROX modalities: If you’re a HYROX athlete, think beyond just running. You can incorporate speed endurance intervals on the ski erg and rower (and maybe other movements??) For instance, after warming up on the ski erg, do 5x100-meter all-out ski erg sprints, each separated by 2-3 minutes rest. While no research yet has directly tested SET on these machines, the principles hold: you’re challenging your anaerobic power and muscular endurance in a way that carries over to race scenarios.

Speed endurance training is just another tool in your toolbox. Use it in the right doses and at the right times and it can yield remarkable results, as both science and anecdotal evidence suggest. There’s a reason pro runners keep strides in their weekly training routines year round. And if you’re well-versed in the double threshold method, you know that there is an “x-factor” speed session included in the weekly training plan.

That’s it for this edition of the Threshold Lab. Happy training!