Lactate Threshold Training: What the Research Shows About Raising Your Threshold

In a classic 1979 study, Farrell and colleagues tested 18 male distance runners in the lab and compared the results with their race times over distances from 3.2 kilometers to the marathon. The best single predictor at every distance was the treadmill speed at which lactate began to accumulate in their blood, with correlations of 0.91 or higher. Adding VO2 max, running economy or muscle fiber type didn't improve the prediction. The marathoners raced only 3 to 7 meters per minute faster than that speed.

That's the case for lactate threshold training, which many people search for as lactic threshold training. Your threshold decides how fast you can go for longer than a few minutes, whether you run, ride, row or climb stairs. If your easy runs feel fine but anything quicker falls apart after 10 minutes, your running lactate threshold is the limit you keep hitting. It responds well to training, and you don't need a lab to train it.

This review covers the training research: who improves and with what dose, why the threshold moves, what your lactate levels mean, how long you can hold threshold effort and how to find your lactate threshold heart rate. For definitions of the first and second thresholds, see our lactate threshold glossary entry. For complete session plans by level, see our tempo run guide.

What Lactate Threshold Training Targets

When a plan says threshold, it almost always means the second lactate threshold: the hardest effort at which your body still clears lactate as fast as your muscles release it. Scientists measure it most strictly as the maximal lactate steady state (MLSS), the highest workload you can hold without blood lactate climbing steadily. Above it, lactate keeps rising until you have to slow down.

Lactate threshold vs aerobic threshold is the most common mix-up. The aerobic threshold, also called the first lactate threshold, is a much easier effort where lactate first rises above resting levels. Training below it builds your base. Lactate threshold training works at the top of the band between the two thresholds, and interval training works above the second one.

The Research: What Studies Show

Beginners improve with almost any steady cardio

If you're starting from little or no exercise, you don't need special threshold sessions. In a trial by Davis and colleagues (1979), nine sedentary middle-aged men cycled 45 minutes a day, about four days a week, for nine weeks. Their anaerobic threshold, a breathing-gas marker of the early lactate rise, went up 44 percent in absolute terms and 15 percent relative to VO2 max. VO2 max itself rose 25 percent, and seven men who didn't train showed no change.

A meta-analysis by Londeree (1997) pooled 85 training groups from 34 studies and reached the same conclusion. Sedentary people improved their lactate and ventilatory thresholds by a very large margin, with an effect size of 2.32 against 0.15 in controls. The intensity they trained at made no significant difference. For them, training near the threshold was enough of a stimulus.

Trained athletes need harder or more specific sessions

Fit people respond differently. In the same meta-analysis, conditioned subjects showed smaller average gains that weren't statistically significant (effect size 0.63). They tended to respond better to high-intensity training than to lower intensities, 1.1 against 0.4. Londeree concluded that once you're trained, a higher intensity may be needed.

That doesn't mean trained athletes stop improving. Two training studies show what moves them:

• One extra threshold run a week. Sjödin, Jacobs and Svedenhag (1982) had eight well-trained middle- and long-distance runners add a single weekly 20-minute treadmill run at the speed that produced 4 mmol/L of blood lactate. After 14 weeks, the speed at that lactate level had risen significantly, with no significant change in VO2 max. Their thigh muscle showed matching enzyme shifts toward aerobic metabolism.
• Harder sessions for a short block. Acevedo and Goldfarb (1989) had seven trained male distance runners raise three sessions a week to 90 to 95 percent of maximum heart rate for eight weeks. VO2 max didn't change (65.3 vs 65.8 mL/kg/min). But 10K times dropped by 63 seconds on average, time to exhaustion at a fixed treadmill speed rose by almost 4 minutes, and blood lactate fell at 85 and 90 percent of VO2 max.

One detail from the Sjödin study helps anyone running threshold sessions. The runners whose lactate rose least during the 20-minute training runs improved the most. Holding a true steady state, rather than drifting above the line, went with bigger gains.

Threshold work moves the threshold more than VO2 max

Helgerud and colleagues (2007) randomly assigned 40 moderately trained men to four programs matched for total work, three sessions a week for eight weeks. The options were long slow running at 70 percent of max heart rate, lactate threshold running at 85 percent, 15-second intervals, or 4-minute intervals at 90 to 95 percent. Only the two interval groups improved VO2 max significantly, by 5.5 and 7.2 percent.

Read together with the Sjödin and Acevedo studies, the pattern is consistent. Threshold training raises how much of your aerobic ceiling you can use for a sustained effort, and intervals raise the ceiling itself. If VO2 max is your goal, our review of how to increase VO2 max covers the interval research.

How much threshold work the evidence supports

Elite athletes give a useful upper bound. A systematic review by Casado and colleagues (2022) found that highly trained and elite distance runners used continuous tempo runs or intervals at the second lactate threshold at least once a week, alongside at least one faster session. Marathoners leaned more on threshold work, and 1,500-meter runners leaned more on fast intervals.

Most of their training still sits well below threshold. Seiler (2010) found that nationally and internationally competitive endurance athletes did about 80 percent of their sessions at low intensity, at blood lactate levels around 2 mmol/L.

When researchers have pitted a threshold-heavy week against a polarized one, mostly easy with some hard intervals, the polarized week has come out ahead. Rosenblat, Perrotta and Vicenzino (2019) pooled the randomized trials in trained athletes and found a moderate advantage for polarized training on time-trial performance (effect size -0.66). Only three trials could be pooled, and the included trials scored 4 or 5 out of 10 on a quality scale, so the edge is suggestive rather than settled. Our polarized training research review covers that debate in depth.

Why Your Threshold Moves: Less Lactate Made, More Cleared

What does lactate threshold indicate? It reflects the balance between how fast your muscles release lactate and how fast the rest of your body takes it up and burns it. Training shifts both sides. MacRae and colleagues (1992) traced labeled lactate in eight untrained men before and after nine weeks of endurance training. At low workloads, below about 60 percent of VO2 max, their blood lactate was lower because their muscles released less of it. At harder workloads it was lower because clearance had risen, with clearance rising from about 31 to 40 mL per kg per minute.

The machinery behind that clearance grows too. In a study by Dubouchaud and colleagues (2000), nine weeks of cycling at 75 percent of peak oxygen uptake raised citrate synthase, a marker of mitochondrial capacity, by 75 percent. The muscle's content of MCT1, a transporter that carries lactate into the cells and mitochondria that burn it, rose by 90 percent. More mitochondria and more transporters mean a given pace produces less lactate and clears it faster, so the threshold moves to a faster pace.

What Your Lactate Levels Mean During Exercise

Lactate levels are reported in millimoles per liter of blood (mmol/L). In a lab test they usually come from a drop taken at a fingertip or earlobe at the end of each stage. The numbers below are common reference points, not personal targets.

The fixed 4 mmol/L marker is a convenience. Beneke, Hütler and Leithäuser (2000) measured the maximal lactate steady state directly in 33 men using repeated 30-minute rides. Lactate at MLSS averaged 4.9 mmol/L with a standard deviation of 1.4, so many riders' true steady-state ceiling sat well above or below 4. It didn't depend on fitness either: the fitter riders held higher workloads at MLSS, but not higher lactate values.

Percentages of VO2 max are just as unreliable. Scharhag-Rosenberger and colleagues (2010) had 21 men ride for an hour at 60 percent and, on another day, 75 percent of VO2 max. Average lactate was 2.1 and 4.6 mmol/L. Individual values ranged from 0.7 to 5.6 at the easier intensity and from 2.2 to 8.0 at the harder one. The same percentage was easy for some riders and above threshold for others, even among riders of similar fitness.

How Long Should You Be Able to Run at Your Lactate Threshold?

Most people can hold their lactate threshold for roughly 35 to 55 minutes, with better-trained athletes toward the longer end. Three lab studies give the range:

• Baron and colleagues (2008): 11 trained men cycling at their maximal lactate steady state lasted 55 minutes on average, with a standard deviation of 8.5 minutes.
• Fontana, Boutellier and Knöpfli-Lenzin (2009): 15 moderately trained men lasted 37.7 minutes cycling and 34.4 minutes running at MLSS, and rated both at about 7 out of 10 for effort.
• Borszcz and colleagues (2018): 23 trained cyclists held 95 percent of their best 20-minute power, the usual functional threshold power estimate, for 50.9 minutes on average, with a standard deviation of almost 16 minutes.

So the old rule of "the pace you could race for an hour" fits well-trained athletes. For moderately trained people, 35 to 40 minutes is closer to the truth. In the Baron study, no physiological system had failed when the riders stopped. Their effort ratings climbed until they chose to quit. That's one reason coaches keep threshold sessions to 20 to 40 minutes of total work, often split into blocks.

Race pace follows from this. If your 5K takes less time than you could hold threshold, which is true for most runners, your 5K pace sits above threshold. If it takes 40 minutes or more, your race effort is close to threshold. A marathon is the opposite case: in the Farrell study, marathoners raced just above the speed where lactate first began to accumulate, well below their second threshold.

Lactate Threshold Heart Rate: How to Find Yours

Lactate threshold heart rate (LTHR) is your heart rate at your second lactate threshold, the effort you could hold for roughly half an hour to an hour. Coaches often place it at about 85 to 92 percent of maximum heart rate. That range is a reasonable first guess, and the research shows why you should replace it with your own number as soon as you can.

Why percentage formulas miss

In a review of how researchers prescribe intensity, Mann, Lamberts and Lambert (2013) concluded that at the same percentage of max heart rate or VO2 max, some people sit above their thresholds and others below them. The Scharhag-Rosenberger data above show the size of that spread. Your threshold heart rate is also sport-specific. In the Fontana study, the same men reached MLSS at an average of 165 beats per minute cycling and 175 running, so a runner's LTHR shouldn't be reused on a bike.

The heart rate bend isn't your threshold

Some field tests look for a bend in the heart rate curve during a ramp test, an idea known as the Conconi test. Jones and Doust (1997) checked it in 14 trained runners. A bend appeared in only nine of them. Where it did, it came at about 95 percent of max heart rate: 186 beats per minute on average, against 172 at the lactate turnpoint. Runners held a speed just below their lactate turnpoint for the full 30 minutes, but a speed just below the bend for only 15.9 minutes on average.

A field estimate that works

The most practical method is a solo effort. After a 15-minute warm-up, run or ride for 30 minutes as hard as you can hold evenly, then take your average heart rate over the final 20 minutes. Endurance coach Joe Friel popularized this version of the test.

Treat the result as an estimate. In the Borszcz study, the 20-minute cycling test matched the lab threshold on average, but individual riders could be off by 30 to 60 watts in either direction. Retest every 6 to 8 weeks, or sooner if your threshold sessions start to feel easy at the same heart rate.

Expect heart rate to creep up during long efforts. Coyle and González-Alonso (2001) describe cardiovascular drift: after 10 to 20 minutes of steady exercise, heart rate rises and the amount of blood pumped per beat falls. In a 30-minute threshold block, set the intensity by pace, power or effort and use heart rate as a ceiling, rather than chasing a fixed number to the end.

How to calculate your heart rate zones from your threshold

Research on endurance athletes, including the Casado review, usually splits intensity into three zones anchored on the two thresholds:

• Zone 1, below your first threshold. You can speak in full sentences. Most of your weekly training time belongs here.
• Zone 2, between the thresholds. Steady and tempo efforts live here, and threshold sessions sit at the top of it, just under your LTHR.
• Zone 3, above your LTHR. Intervals and races shorter than about half an hour.

This research zone 2 is a different band from the popular "zone 2" of five-zone systems, which sits below the first threshold. If you only know your LTHR, keep easy days comfortably below it, at an effort where you could hold a conversation, and keep threshold sessions within a few beats of it. Watches that build five or seven zones from the same number are slicing these three zones more finely.

How Lactate Threshold Training Works in Practice

If you're new or returning

Build consistency before intensity. Three to five sessions a week of 30 to 45 minutes of steady cardio, at an effort where you can talk in sentences, is close to the program that raised the threshold by 44 percent in the Davis trial. Once that feels routine, usually after 6 to 8 weeks, end one session a week with 10 to 15 minutes at an effort where you can only speak in short phrases.

If you already train regularly

Add one threshold session a week, as the Sjödin runners did, and keep the rest of the week mostly easy. These formats all work:

• Continuous: 20 to 30 minutes at threshold effort.
• Cruise intervals: 3 or 4 blocks of 8 to 10 minutes, with 1 to 2 minutes of easy movement between them.
• Sub-threshold intervals: more, shorter blocks held a little below threshold, for more total time with less fatigue.

Aim for a steady state. If the last block feels much harder than the first, start the next session slightly slower. The tempo run guide linked above has warm-ups, pacing checks and a progression for each level. A short block of harder work can follow, as in the Acevedo study, but treat three sessions a week at 90 to 95 percent of max heart rate as a 6- to 8-week block, not a permanent routine.

Lactate threshold training at home

You don't need a track. Any steady cardio that uses large muscle groups can hold you at threshold: a stationary bike, a treadmill, a rowing machine, stair climbing, brisk uphill walking, or a continuous low-impact circuit of marching, step-ups and skater steps. Cycling and running produced almost the same time to exhaustion at MLSS in the Fontana study, so the effort carries over between modes for general fitness. Runners preparing for a race should still do most threshold work on foot.

The rest of the week matters as much as the threshold day. If you'd like your strength, mobility and easy cardio days planned for you, an AI personal trainer app can carry that structure: FitCraft's AI coaches build a personalized plan around your goals and schedule, demonstrate each exercise in interactive 3D, and adapt your workouts as you progress.

Common Misconceptions

Misconception 1: "Lactic acid causes next-day soreness"

Next-day soreness tracks muscle damage from lowering-type (eccentric) contractions. Schwane and colleagues (1983) had seven people run for 45 minutes on the level at 78 percent of VO2 max and, on another day, downhill at only 57 percent. The easier downhill run caused significant soreness and a 351 percent rise in the muscle enzyme CPK a day later. The harder level run caused neither.

Misconception 2: "Threshold training teaches you to tolerate more lactate"

Training mostly lowers the lactate a given pace produces. In the MacRae study, trained muscles released less lactate at easy workloads and the body cleared it faster at hard ones. In the Acevedo runners, lactate fell at the intensities they had trained at. You end up making less and clearing more at the same pace, which is why the threshold moves.

Misconception 3: "If threshold work is good, more of it is better"

In the Helgerud trial, threshold running at 85 percent of max heart rate didn't raise VO2 max any more than easy running did. In the Rosenblat meta-analysis, threshold-heavy weeks lost to polarized ones on time trials. One or two threshold sessions a week, inside a mostly easy week, is the pattern elite distance runners use.

What the Research Suggests Going Forward

The core findings are consistent. Beginners raise their threshold with almost any regular cardio. Trained athletes keep raising it with a weekly session at or near threshold, or a short block of harder work, often with no change in VO2 max. The adaptations sit in the muscle: more mitochondria, more lactate transporters, less lactate made and more cleared at a given pace.

The limits are real too. Most training studies enrolled fewer than a dozen people, mostly young men, and they used different threshold definitions. A 2020 review by Jamnick and colleagues found little evidence that most common threshold methods accurately mark the boundary between heavy and severe exercise, with critical power and critical speed as the exceptions. Expect your measured threshold to vary by method and by day.

The practical answer is simple. Keep most of your week easy, add one threshold session, and repeat a field test every couple of months. The number to watch is the pace or power you can hold at a steady threshold effort, and it should rise over months rather than between two tests.

References

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