Lactate threshold is the exercise intensity where lactate builds up in your blood faster than your body can clear it. Below that line, effort feels controlled and you could go for a long time. Above it, the burn arrives, breathing gets ragged, and the clock starts ticking. It's the physiological border between easy cardio and hard cardio.

What is lactate threshold?

Lactate threshold, which many people type as lactic threshold, is the hardest effort you can hold while your body still clears lactate as fast as your muscles make it. Your muscles produce lactate all the time, even at rest, and your heart and other muscles burn it as fuel while your liver turns some of it back into glucose. In a review of decades of lactate shuttle research, Brooks (2018) describes lactate as a major energy source and signaling molecule rather than a waste product. The threshold is simply the point where production starts to outrun that clearance.

Much of the confusion comes from there being two thresholds. Faude, Kindermann and Meyer (2009) found 25 different lactate threshold definitions in the research and grouped them around two breakpoints that every incremental test passes through:

When a coach, a training plan or a watch says lactate threshold without a number, it almost always means LT2. Threshold pace, threshold heart rate and threshold runs all refer to that second line.

Why it matters

Quick clarification first: lactate isn't the villain it was made out to be. It's actually a fuel your body recycles. The threshold matters because it marks where clearance can't keep up, and everything that comes with high-intensity effort piles on from there.

Among people with similar fitness, your threshold predicts endurance performance better than VO2 max does. Coyle and colleagues (1988) tested 14 competitive cyclists with almost identical VO2 max scores. Seven reached their lactate threshold at about 66 percent of VO2 max and seven at about 82 percent, and at the same hard workload the high-threshold group lasted more than twice as long (61 minutes against 29). It's also the anchor for training zones: zone 2 sits just below your first lactate turn point, and tempo work sits near the second. Ride your easy days above threshold and they stop being easy days. That's the most common cardio mistake there is.

How to find your lactate threshold

The most precise way is a lab test. You run on a treadmill or ride a bike while the intensity rises in stages of a few minutes, and a drop of blood from a fingertip or earlobe is tested for lactate at the end of each stage. Plotted against pace or power, lactate stays almost flat, then bends upward. LT1 is read where the curve first lifts off its baseline. LT2 is read from the bend, or from a fixed value such as 4 mmol/L. A fixed value is quick, but thresholds differ from person to person, so it can land above or below yours.

You can get close without a lab:

What is a good lactate threshold?

A good lactate threshold is a high one relative to your own aerobic ceiling, so it's easiest to compare as a percentage of VO2 max. In their review of champion endurance physiology, Joyner and Coyle (2008) put the lactate rise at about 60 percent of VO2 max in untrained people and at 75 to 90 percent in trained endurance athletes. Moving up that range is most of what endurance training does for you.

What is the threshold heart rate?

Threshold heart rate is your heart rate at lactate threshold, and it's personal. In 31 trained male runners studied by Weltman and colleagues (1990), the first lactate rise came at an average of 166 beats a minute, about 88 percent of their average maximum of 187, and the 4 mmol/L mark came at 182, about 97 percent. Most of them didn't cross the first threshold until they reached 90 percent of max heart rate. A fixed percentage of max can miss your threshold by a wide margin, which is why a 30-minute test beats a formula.

What is the difference between threshold pace and 10K pace?

Threshold pace is roughly the pace you could race for about an hour. If you run 10K in 40 minutes, your threshold pace is a little slower than your 10K pace. If a 10K takes you close to an hour, the two are about the same. For many recreational runners, threshold pace falls between 10K and half marathon pace.

How to use it in training

You don't need a blood test. Use the talk test: below threshold you can speak in full sentences, near it you get short phrases, above it you get single words.

To raise it, spend most of your cardio time below it (easy zone 2 volume) and add one weekly tempo session at or just under threshold: 20 to 40 minutes at a comfortably hard, sustainable pace. Over months, the pace you can hold at that same effort creeps up. That creep is the whole game.

The research backs that up. Londeree (1997) pooled 34 training studies and found that sedentary people raised their threshold substantially when they trained at or near threshold intensity. Already-fit people improved less and tended to respond better to harder sessions, so add short intervals once a weekly tempo session stops moving your pace. Our guide to the tempo run has threshold workouts by level, including cruise intervals that split the effort into repeats of 8 to 10 minutes.

Related terms

Go deeper

See how threshold anchors easy training in our research breakdown: Zone 2 training research. For threshold sessions you can run this week, read our tempo run guide.

Frequently Asked Questions

What is lactate threshold pace?

Lactate threshold pace is the fastest running pace you can hold while lactate production and clearance stay in balance. For trained runners it's roughly the pace they could race for about an hour, which sits between 10K and half marathon pace for many recreational runners. The average pace of a hard, evenly paced 30-minute solo run is a good estimate.

Is lactate threshold the same as aerobic threshold?

Not usually. The aerobic threshold is the first lactate threshold (LT1), where blood lactate first rises above resting levels at an easy, conversational effort. When coaches and watches say lactate threshold, they usually mean the second one (LT2), the hardest effort you can sustain before lactate climbs steadily.

What does lactate threshold indicate?

It shows how much of your aerobic ceiling you can use for a sustained effort. Two athletes with the same VO2 max can perform very differently because one reaches threshold at a higher percentage of it. It also anchors training zones: easy work sits below the first threshold and tempo work sits near the second.

What's more important, VO2 max or lactate threshold?

For races longer than a few minutes, lactate threshold often decides the result among people with similar VO2 max. In a study of 14 cyclists with nearly identical VO2 max scores, those whose threshold came at about 82 percent of VO2 max lasted more than twice as long at a hard workload as those at about 66 percent. VO2 max sets the ceiling, and threshold sets how much of it you can use.

Can you improve lactate threshold?

Yes, and it responds well to training. A meta-analysis of 34 studies found large gains in sedentary people who trained at or near threshold intensity, and smaller gains in people who were already fit, who tended to respond better to harder work. Easy volume plus one weekly tempo or threshold session is the usual approach.

What is a lactate threshold run?

A lactate threshold run, also called a tempo run, is a sustained effort at or just below your second lactate threshold, usually 20 to 40 minutes continuous or split into repeats of 8 to 10 minutes with short easy jogs between. It should feel comfortably hard: you can say a short phrase but not hold a conversation.