Ask ten runners what they should do to get faster and most will point at one of two extremes. Go easy and pile on the kilometres, or go hard and hurt. Both matter. But the pace that quietly does more than either sits right in between them, and it is the one most people either skip or ruin. That pace is threshold.
This is the long version. What threshold really is, why it is so productive, how to find yours, and exactly how the session scales from your first structured workout up to the double-threshold days that build Olympic finalists.
What threshold actually means
Every time you run, your muscles produce lactate and your body clears it away and reuses it. At easy paces, clearance keeps up effortlessly. Push harder and you eventually reach a tipping point where lactate starts to build faster than you can remove it. That tipping point is your lactate threshold.
Practically, threshold is the fastest pace you can hold in a metabolic steady state. The effort you could sustain for roughly an hour before it starts to run away from you. Sport scientists usually describe two markers along the way. The first, often called LT1 or the aerobic threshold, is the lower turn point where lactate first creeps above resting levels. The second, LT2 or the anaerobic threshold, sits higher, close to what is called maximal lactate steady state, where lactate starts to climb sharply. When runners say "threshold," they almost always mean that second marker, LT2 (Faude and colleagues, 2009).
Those turn points are pinned down by measuring how much lactate is in a pinprick of blood, reported in millimoles per litre, or mmol/L. At rest you sit around 1, LT1 lands near 2, and LT2 tends to fall somewhere around 4, though the exact numbers shift from one runner to the next. That is the figure a handheld lactate meter reads, and it is why you will see thresholds and hard sessions described in millimoles, not just in pace.
The lab definitions get technical, and different testing methods disagree on the exact numbers. But the training idea underneath is simple and hard to break: threshold is controlled, comfortably hard, sustainable effort. Not easy. Not a sprint. The pace you could just about live with.
Why it is the pace that builds racers
Train near threshold and you push the tipping point itself out to a faster pace. The whole lactate curve shifts to the right, so an effort that used to bury you becomes something you can hold (Jones and Carter, 2000). Three things improve at once: your muscles get better at clearing and burning lactate as fuel, your running economy sharpens, and you can hold a higher fraction of your VO2max for longer.
It is also the most race-specific fitness you own. Almost everything from a 10k to a marathon is run at or just around threshold, so time spent there translates about as directly to the clock as training gets.
And it is efficient. Threshold work sits just below the intensity that truly shreds you, which means you can absorb far more of it than all-out intervals without digging a deep recovery hole. More productive work, less wreckage. That combination is why it earns a bigger slice of a serious training week than any other kind of hard running.
Threshold is where you spend the currency that actually shows up on race day.
How to find yours without a lab
You do not need a lactate meter to train threshold well. A handful of body cues will get most runners close enough:
- Pace. Roughly the pace you could race for about an hour. For many runners that lands near their current 10k to half marathon effort.
- Talking. You can force out a short, broken sentence, but you would not want to hold a conversation.
- Breathing. Deep and rhythmic, clearly working, but still under control. You are not gasping.
- Effort. About 7 to 8 out of 10. It should feel like something you could hold if you truly had to, but would rather not.
- Heart rate. Very roughly 85 to 90 percent of maximum, though this drifts through a session and is the least reliable of these markers on its own.
A recent race result or a lactate test will sharpen the number if you want it. But those cues are enough to train off week to week.
The one rule that separates good threshold work from bad
The most common mistake is running threshold sessions too hard. Hammering feels productive, but the moment you tip well past that second turn point you are no longer doing threshold work. You are doing a hard interval session wearing a threshold label, and you pay for it in fatigue that bleeds into the rest of your week.
The best programs treat threshold as controlled volume instead. The Norwegian approach that has produced world and Olympic champions keeps the effort in a tight, deliberately sub-maximal lactate window and accumulates a lot of it, rather than red-lining a handful of reps (Casado and colleagues, 2024).
The practical version is a single sentence: finish every threshold session feeling like you could have done one or two more reps. Leave a little in the tank, every single time. Over weeks, that controlled consistency out-builds heroics by a distance.
What a session actually looks like
The dose scales with your training age and weekly volume, but the shape stays the same. Broken efforts at a controlled threshold, short recoveries, adding up to a meaningful chunk of quality time. Warm up and cool down easy for 10 to 15 minutes either side of every one of these.
Beginner. New to structured intensity, or running roughly 25 to 40 kilometres a week. Start with one threshold session a week. Twelve to twenty minutes of quality is plenty.
- 4 x 5 minutes at threshold, with 60 to 90 seconds of easy jogging between.
- Or a single continuous 15 to 20 minute tempo at a slightly softer, comfortably hard effort.
Intermediate. A few seasons of consistent running, roughly 50 to 80 kilometres a week. One to two threshold sessions a week, 25 to 40 minutes of quality.
- 5 x 8 minutes at threshold, 90 seconds easy between.
- Or 5 x 1600 metres at threshold with 60 to 75 seconds recovery.
- Or 2 x 15 minutes continuous, with 3 minutes easy between.
Advanced and elite. High volume, 100-plus kilometres a week, built on years of base. Two threshold sessions a week, sometimes split across one day as a double, totaling 40 to 70-plus minutes of quality.
- A double-threshold day: morning 5 x 6 minutes, evening 10 to 12 x 1000 metres, all at a controlled, deliberately sub-maximal effort.
- Lactate is often held in a tight 2.5 to 3.5 mmol/L window so the work stays repeatable day after day.
- This is the engine behind the Norwegian method, and it only works stacked on top of a very large easy-running base.
These are templates, not prescriptions. The right starting point is the smallest dose you can recover from and repeat, not the biggest one you can survive once.
Where it fits in your week
Threshold is not a stand-alone trick. It works because it sits on a foundation of easy running. Keep the bulk of your week genuinely easy, which is harder than it sounds and worth its own read in why your Zone 2 is probably too hard, then protect one or two threshold days and let the rest of your running support them.
When you progress, add volume before pace. Put in another rep, or stretch the intervals a little longer, before you try to run them faster. The threshold itself keeps moving as you train. Chase that, not the stopwatch on any single day.
Done consistently, threshold work is about the closest thing distance running has to a cheat code. It is the pace that turns fitness into finishing times. If you are not sure whether your engine, your durability or your fueling is the thing actually holding you back, the free 2 minute assessment will tell you, along with the first change to make.