What Is Sweet Spot Training? A Science-Based SST Guide for Runners

Sweet spot training has a cult following in cycling — and it turns out, the same principles apply to running. For full marathon performance, lactate threshold (LT) is one of the most important physiological markers. LT marks the point at which blood lactate concentration begins to rise sharply with increasing exercise intensity.

LT matters for marathon performance, but its role goes further than that. It’s also central to training efficiency — getting the maximum physiological benefit from the minimum amount of fatigue.

Training at or just below the lactate threshold is called sweet spot training (SST). SST is a high-reward, low-fatigue training method — one of the best returns on investment in running.

The term is rarely used in the running world, but it’s extremely well-known among cyclists. This article explains the benefits of SST and how to implement it in your running training.

Understanding Lactate Threshold (LT)

To make sense of this article, you need to understand lactate threshold (LT).

LT is the point at which blood lactate concentration begins to rise sharply as exercise intensity increases. The chart below illustrates this relationship.

A full explanation of LT is beyond the scope of this article, but if you’d like to go deeper, the article below covers it in detail.

LT typically falls in the blood lactate range of 2.0–4.0 mmol/L, which corresponds to roughly 83–87% of max heart rate. Keep in mind that heart rate varies significantly with age and ambient temperature, so treat these numbers as guidelines rather than exact targets.

Three key factors determine distance running performance: VO2 max, lactate threshold (LT), and running economy.

Bassett & Howley (2000) ※1 reported that LT running speed is the single best physiological predictor of endurance performance, integrating all three factors.

Sustained training at or near the lactate threshold — as in SST — can raise your LT over time. In practical terms, this means your blood lactate rises less steeply at any given pace.

What Is Sweet Spot Training (SST)?

Here’s a closer look at sweet spot training (SST) — one of the most efficient methods for raising your lactate threshold.

How SST Is Defined

In the cycling world, SST is defined as training at 88–94% of FTP (Functional Threshold Power). FTP stands for Functional Threshold Power — the maximum power output you can sustain on a bike for one hour. Translated to running, the one-hour sustainable effort corresponds to your threshold pace.

Mapping 88–94% FTP onto running puts the sweet spot right around marathon pace. But SST in running isn’t limited to marathon pace. That’s simply what happens when you hold a steady pace continuously — marathon pace happens to land in the SST intensity zone.

By combining appropriate interval distances with recovery periods, you can run SST at paces faster than marathon pace. The key is managing blood lactate, not pace per se.

Real-World Proof: The Ingebrigtsen Brothers

One of the clearest examples of SST in action comes from the Norwegian middle-distance scene. Jakob Ingebrigtsen has dominated global middle- and long-distance running by incorporating SST principles into his training.

His brothers Henrik and Filip are equally impressive middle-distance runners, and all three have produced remarkable results using the same training philosophy.

The theoretical foundation behind the Ingebrigtsen brothers’ training is coach Marius Bakken’s model. Bakken specifically discusses the sweet spot in the context of running performance.

The training model he advocates — double threshold training — involves two threshold sessions per day. Precise intensity control is essential to make this work without accumulating excessive fatigue.

Double threshold training is designed to keep blood lactate in exactly the SST range throughout both sessions.

Bakken’s model states that keeping blood lactate in the 2.3–3.0 mmol/L range during training minimizes fatigue while maximizing adaptation.

The diagram below shows what the 2.3–3.0 mmol/L sweet spot looks like on the lactate curve.

Running SST as Intervals — Go Faster Than Marathon Pace

By the cycling definition, the sweet spot intensity corresponds to roughly full marathon pace when running continuously.

The key point not to miss: that intensity is based on running continuously at that pace. It doesn’t mean your SST pace is capped at marathon pace.

By splitting the effort into intervals, you can run SST at paces faster than marathon pace while keeping blood lactate in the sweet spot range. Here’s how the Norwegian model structures this.

The double threshold training used in Norway is structured as follows.

Both sessions are performed so that blood lactate stays in the 2.0–3.0 mmol/L range. By using intervals, you can push the pace above marathon pace while keeping lactate within the sweet spot zone.

My SST Data: Intervals Keep Blood Lactate in Check

I was inspired by this approach and decided to test it on myself. I’ve been measuring blood lactate during training sessions, and the data confirmed it: splitting the effort into intervals does bring lactate down significantly.

At the time of this session, 5:46/mile(3:35/km) was faster than my half marathon race pace. Even so, blood lactate stayed below 4.0 mmol/L throughout the workout.

The Biggest Benefit: Minimal Fatigue

The standout feature of sweet spot training is how little fatigue it produces. I used to assume that running faster meant accumulating more fatigue — but SST proved that assumption wrong.

What I found was that as long as you keep blood lactate below a certain threshold — which intervals make possible — fatigue stays surprisingly low even at faster paces.

Here’s a more recent example from my own training.

In this session, I ran 6:02/mile(3:45/km) intervals on a treadmill. 6:02/mile is roughly my marathon pace. Running a 42-minute continuous tempo run at 6:02/mile leaves noticeable fatigue the next day — but by splitting it into intervals, I could hold marathon pace while keeping blood lactate in check.

Next-day fatigue was minimal. I felt ready to do another quality session back-to-back, and I actually did a short interval workout the following day with no drop in training performance.

How to Run Sweet Spot Workouts

Here’s a practical guide to implementing SST in your training.

Sample SST Workouts

The table below shows four SST workout structures ranging from moderate-low to moderate-high intensity.

Workout	Rest	Pace	Est. Heart Rate	Intensity Zone
① 10 min × 3–4	60 sec	Full marathon pace or faster	~85% max HR	Moderate-low
② 6 min × 5–6	60 sec	Half–full marathon pace	~85% max HR	Moderate-low
③ 3 min × 10	60 sec	10K–half marathon pace	~89% max HR	Moderate-high
④ 1 min × 25	30 sec	5K–10K race pace	~87% max HR	Moderate-high

Workouts ① and ② fall in the moderate-low zone; ③ and ④ are moderate-high.

Even for faster workouts like ③ and ④, staying at or below the target heart rate keeps blood lactate under 3.5 mmol/L — well within the SST range.

The critical factor in running SST is holding intensity below a certain ceiling. For most recreational runners, heart rate is the only metric available in real time. Use it consistently.

The goal is to quantify your effort — not just rely on feel. A reliable heart rate reading lets you verify that your perceived effort matches your actual physiological intensity.

How Hard Does SST Feel?

SST isn’t particularly hard. The subjective effort is somewhere around “comfortably challenging — tough but not desperate.”

During the run itself, you’ll feel very little discomfort. When using intervals, the final few reps might bring a slight heaviness in the legs — but nothing that makes you want to stop. On a 1–10 effort scale, most people would rate SST around a 4–5.

The day after an SST session, fatigue is minimal. You’ll likely feel like you could do another SST session that same day, let alone the next.

How to Set Your Target Pace and Interval Length

The target pace range for running SST runs from 5–10 seconds per km slower than full marathon pace up to just below 5K race pace.

Your actual pace depends heavily on how long each interval rep is. Shorter reps allow you to run faster while keeping blood lactate in the sweet spot — because lactate doesn’t have time to accumulate as much.

Here are the general guidelines for pairing pace with interval length.

Target a total running time of 25–40 minutes across all reps. Going beyond that risks accumulating too much fatigue and defeats the purpose of SST.

Rest Between Intervals

Recovery between SST reps can be a walk or a very easy jog. This is not a workout where you push through the rest — the whole point is to keep intensity controlled.

Cautions and Common Mistakes

A few things to watch out for when doing SST effectively.

The Overtraining Trap

SST can creep into overtraining without you noticing. The effort feels manageable, which makes it tempting to push a little harder each rep.

A 4–5 out of 10 effort feels easier than you might expect. It’s common to think “I could go a bit faster” and gradually bump up the pace rep by rep — until you’ve accumulated more fatigue than intended.

Keeping intensity capped is the whole point of SST. If you can measure blood lactate, you can calibrate feel against actual intensity precisely. Without that, you’ll need to run SST repeatedly to develop a sense of the effort level that doesn’t leave you overly fatigued.

SST Alone Won’t Make You Faster

SST on its own has limits. Doing nothing but threshold-zone work may not be enough to keep improving.

Stöggl & Sperlich (2014) ※2 divided 48 endurance athletes (runners, cyclists) into four groups and compared training approaches over nine weeks. Polarized training — 80% low intensity plus 20% high intensity — produced greater VO2 max gains than threshold training alone. The threshold-only group showed no significant improvement in VO2 max.

A network meta-analysis using individual-level data (Rosenblat et al., 2025) ※3 further confirmed that polarized training produced the largest improvements in both VO2 max and time-trial performance among endurance athletes.

The takeaway: pairing threshold-zone training with some higher-intensity work is important. SST is an effective tool for building aerobic capacity with low fatigue, but it’s not a complete training program on its own.

Performance here means metrics like VO2 max and running velocity at 4 mmol/L blood lactate.

The examples in the next section show that athletes who combine SST with higher-intensity work see the greatest performance gains.

SST Already in Your Training (You Just Didn’t Know It)

Let’s look at some examples of SST already being used — often without the runner even calling it that.

Sweet spot training (SST) is a term borrowed from cycling, so it rarely appears by name in running training plans. But many common running workouts already operate at SST intensity.

Norwegian Double Threshold Training

The Norwegian double threshold training introduced earlier is the clearest example of SST in running. Elite runners keep blood lactate in the 2.3–3.0 mmol/L range throughout training, which is said to minimize fatigue while maximizing aerobic adaptation.

The “adaptation” referred to here is specifically an improvement in aerobic metabolic capacity.

A separate article on this site covers Jakob Ingebrigtsen’s training in detail — he’s the most prominent example of an elite runner who has thrived using the Norwegian double threshold model.

Kenyan Training Culture

Coach Marius Bakken has written on his website (mariusbakken.com) about observing Kenyan runners in training. According to him, SST-intensity running appears naturally and intuitively in how Kenyan runners train day to day.

Kenyan runners have a highly refined sense of effort. Their everyday training intensity naturally gravitates toward the sweet spot zone — not because they’re measuring lactate, but because they’ve developed an intuitive feel for the right effort level.

This ability to stay in the sweet spot while accumulating training volume — without building up fatigue — may be one of the key reasons Kenyan runners can train so consistently.

The Brisk Jog

The “brisk jog” — a run that feels like an easy jog but at a faster-than-normal pace — is itself a form of sweet spot training.

Most runners who do brisk jogs don’t push all the way to marathon pace, but many naturally drift up toward marathon pace as the run feels good. That drift lands them squarely in the SST intensity zone.

Because fatigue the next day is low, the runner mentally files it as “just a jog” — but physiologically, it’s doing meaningful threshold work. This may also explain why runners tend to feel especially good on those days when the jog naturally picks up pace.

The brisk jog is also called a moderate run or moderate-intensity run. There’s some overlap with the SST zone, which I cover in a separate article.

If you’ve been stuck at a performance plateau, or if high-intensity training has been leaving you injured, SST is worth adding to your rotation.

References

※1 Bassett DR Jr, Howley ET (2000) “Limiting factors for maximum oxygen uptake and determinants of endurance performance” Med Sci Sports Exerc

※2 Stöggl T, Sperlich B (2014) “Polarized Training Has Greater Impact on Key Endurance Variables Than Threshold, High Intensity, or High Volume Training” Front Physiol

※3 Rosenblat MA et al. (2025) “Which Training Intensity Distribution Intervention will Produce the Greatest Improvements in Maximal Oxygen Uptake and Time-Trial Performance in Endurance Athletes?” Sports Med