Threshold run: what it is, how to pace it, and tempo vs threshold

The threshold run is the workout most runners think they're doing and few actually do. Half of them run it so hard it turns into a race. The other half run it so gently it's just a slightly brisk Tuesday.

So what is a threshold run? A sustained effort at roughly the hardest pace you can hold before fatigue starts snowballing: comfortably hard, a few words at a time, finished feeling like you could have done a bit more. That's the threshold run meaning in one sentence. The rest of this post covers how to pace one, the classic sessions, tempo vs threshold run (they're cousins, not twins), and where it fits in a week that also has lifting in it. If you'd rather not juggle all of that yourself, that's the job of a running app with strength built in.

What is a threshold run?

As you run faster, your body passes two turning points. The first is where blood lactate starts rising above resting levels. The second is the highest intensity where lactate production and clearance still balance out. Above that second point, lactate keeps climbing and the clock on your effort starts ticking. A review of lactate threshold concepts describes exactly this two-breakpoint picture (Faude, Kindermann and Meyer, 2009). When runners say "threshold", they mean the second one.

A threshold run sits right around that second turning point. In the five-zone model we use on this blog, that's zone 4, roughly RPE 7–8. If you want those bands in beats per minute, calculate your heart rate zones from your max heart rate:

For the physiology, testing options and how to raise the number itself, a guide to lactate threshold covers the full picture. This post is about the workout.

Why "about an hour" is the usual rule of thumb

Coaches often describe threshold effort as roughly what you could race for about an hour. There's a lab reason for that. When trained cyclists rode at their maximal lactate steady state until they couldn't continue, they lasted 55 minutes on average (Baron et al., 2008). A threshold run asks for a chunk of that effort, not all of it, which is why 20–30 minutes at threshold should leave you tired but not wrecked.

How to pace a threshold run

There are three ways. Use at least two of them to cross-check.

By feel

This is the most underrated method. Threshold feels like:

• ›You can say a few words, not full sentences.
• ›Breathing is deep and rhythmic, but under control.
• ›It feels sustainable for a while, then suddenly not.

That's RPE 7–8. Subjective markers aren't as crude as they sound: a 2022 review found that RPE and the talk test are valid markers of the respiratory compensation threshold, the ventilatory cousin of lactate threshold (Bok, Rakovac and Foster, 2022).

By heart rate

Aim for zone 4. Two quirks: heart rate takes a few minutes to catch up at the start of a rep, so don't chase the number early, and it drifts upward late in long efforts, so a small rise at the same pace is normal.

The more accurate anchor is your own threshold heart rate rather than an age formula. The short version of our guide to lactate threshold heart rate: run a hard, solo 30-minute effort, press lap at 10 minutes, and take your average heart rate for the last 20 minutes as your estimate. Anchor to a test, not to your birthday.

By pace

If you've raced recently, your threshold pace is somewhere around the pace you could hold for an hour. For many recreational runners that lands a little slower than 10K race pace, and much slower than 5K pace. Pace is the least forgiving method, though: it ignores hills, heat and wind. On a hot or hilly day, run by feel and let the pace drop.

Threshold run workouts

All of these start with 10–15 minutes easy and finish with 10 minutes easy.

Splitting threshold work into reps with short jogs lets you accumulate more time at the right effort with less fatigue than one long block. That's why cruise intervals are the default for most people.

Progress by adding time at threshold, a few minutes a week, not by running the reps faster. Faster reps turn a threshold session into an interval session.

Tempo vs threshold run

This is where the confusion lives. Some coaches use the words interchangeably. Most draw a line like this:

So in the threshold vs tempo run question, threshold is a slightly sharper, more precise effort, and tempo is a slightly longer, steadier one. Both train the same quality: holding a strong pace for a long time. If you want to see how we define tempo run workouts and how long to make them, that's its own post.

For most recreational runners, the difference matters less than the principle: neither should be a race, and neither should be every run.

Where threshold runs fit with intervals and VO2 max

Threshold work raises how much of your engine you can use for a long time. Intervals raise the size of the engine. You want both, in proportion.

The proportion is smaller than people think. In one detailed study of well-trained junior cross-country skiers, only about 8% of endurance sessions by heart rate fell between the two thresholds, with most sessions clearly below and a smaller share well above (Seiler and Kjerland, 2006). The authors' summary: elite endurance athletes train surprisingly little at lactate threshold intensity.

And threshold work alone won't max out your ceiling. In Helgerud et al. (2007), a group training at lactate threshold (85% of max heart rate) improved VO2 max less than groups doing intervals at 90–95% of max with the same total work. If your threshold sessions have stopped moving the needle, the next lever is usually a small weekly dose of zone 5. That's how to increase VO2 max, explained in one line: a bigger ceiling lifts everything under it.

A few related reference points:

• ›Where your aerobic ceiling sits compared with others your age is what a VO2 max chart is for.
• ›The sessions that raise that ceiling are VO2 max training: shorter, harder intervals, mostly in zone 5.
• ›Choosing between the two each week is the short version of our guide to tempo run vs interval run: threshold work for longer races and holding pace, intervals for shorter races and a bigger ceiling.
• ›For a cheap field estimate of your ceiling, a Cooper test VO2 max estimate comes from running as far as you can in 12 minutes, a method first validated against treadmill testing by Cooper (1968).

Threshold runs for hybrid athletes

If you lift, a threshold run is a hard day. A 30-minute threshold session sits in the same weekly fatigue budget as heavy squats.

• ›Keep threshold runs away from the day before or after your heaviest lower-body session.
• ›If you must double up, pair a threshold run with upper-body lifting, and run first if running is the priority.
• ›In a strength-focused block, one threshold session a week holds your running fitness.
• ›In a running-focused block, one threshold run plus one interval session is plenty, with everything else easy.

Common threshold run mistakes

• ›Racing it. If you finish a threshold run unable to speak, it was an interval session in disguise.
• ›Running it too often. Once a week for most people. Twice is a ceiling, not a target.
• ›Chasing heart rate on short reps. Heart rate lags. Use feel for the first few minutes of each rep.
• ›Ignoring conditions. Same pace on a hot day is a harder run. Hold the effort, not the number.
• ›Turning easy days into threshold days. Your threshold session only works if the runs around it are actually easy.

How exrsz handles threshold runs

exrsz builds a periodized plan from your goal, schedule, level and equipment, and threshold runs show up as planned hard days with easy running around them. It balances them against your lifting in one plan so they don't land next to heavy leg days, adapts each week to how you actually trained, and reshuffles missed sessions instead of stacking two hard runs together.

FAQ

What is a threshold run?

A threshold run is a sustained effort at roughly your lactate threshold: zone 4, RPE 7–8, where you can say a few words but not hold a conversation. It's usually 20–30 minutes at that effort, continuous or split into reps.

What is the difference between a tempo run and a threshold run?

A threshold run sits right at your second threshold, often in reps; a tempo run is usually a slightly easier, longer continuous effort just under it. Many coaches use the terms loosely, but both should feel controlled, not raced.

How long should a threshold run be?

Most threshold sessions include 20–30 minutes at threshold effort, plus a warm-up and cool-down. Beginners can start with 3 × 5 minutes and add time gradually.

What heart rate should a threshold run be?

In the five-zone model based on max heart rate, threshold sits in zone 4, at about 80–90% of max (Helgerud et al., 2007 used 85% of max as their lactate threshold intensity). A field-tested threshold heart rate is more accurate than an age formula.

How often should I do threshold runs?

Once a week works for most recreational runners, and twice is plenty even for experienced ones. Keep the rest of your running mostly easy.