Most coaches already know what a lactate test is. The harder question is whether it belongs in your coaching practice, or whether it stays in the “nice to have, too expensive, too fiddly” bucket next to VO2max assessments and muscle oxygen sensors.
If you read through discussions among serious amateurs, you see the same pattern again and again. An athlete pays for a one-off lab test, gets a report with heart rate zones, finds the numbers broadly match what they expected, and concludes the test was not really worth it. The takeaway most of them land on is that a single test is an expensive snapshot.
That conclusion is correct for athletes testing themselves in isolation. It misses the point for coaches. Lactate testing is not primarily an athlete tool. It is a coaching tool, and the value shifts dramatically once a coach owns the protocol, interprets the data, and applies it across a training block.
The guesswork problem
The main reason to use lactate testing in coaching is that nearly everything else you do to set zones is educated guessing.
Heart rate zones from maximum heart rate formulas are a rough estimate. Karvonen is slightly better, but still a formula. FTP from a 20-minute test gives you one number and assumes a fixed relationship between that number and your athlete’s physiological threshold. VDOT from a recent race is useful, but it collapses an entire metabolic profile into a single pace.
These methods work well enough for most athletes most of the time. They also quietly fail in ways coaches do not always catch.
A recurring story in advanced running communities is athletes who discover, after a lab test, that their “easy” Zone 2 runs were actually deep Zone 1. One runner described shifting their easy pace from 8:45 per mile to 7:20 per mile after testing, and immediately starting to see progress in workouts that had stagnated for a year. Others discover the opposite: their threshold sessions were consistently above LT2, grinding them into a hole without producing the intended adaptation.
As a coach, this is your blind spot if you only work from formulas and race results. A lactate test converts that blind spot into two concrete numbers: the aerobic threshold (LT1) and the anaerobic threshold (LT2). Your training prescription is no longer a guess that happens to be close. It is a prescription that matches the athlete’s physiology.
What the test actually tells you that nothing else does
A well-executed lactate test gives you more than thresholds. It gives you a curve, and the shape of that curve is where the coaching insight lives.
Two athletes can have the same LT2 and completely different profiles. One might have a wide gap between LT1 and LT2 with a gradual curve, pointing to a strong aerobic base and room to develop top-end work. Another might have a compressed gap and a steep curve, indicating an athlete who is producing too much lactate too early and needs aerobic development before anything else.
You cannot see this from a 5K time. You cannot see it from heart rate data alone. You can guess at it based on training history and race results, and experienced coaches often guess well, but guessing well is not the same as knowing.
The curve also tells you something about the athlete’s lactate production rate, often discussed as VLa Max. For a short-course triathlete or a middle-distance runner, high glycolytic output is an asset. For an Ironman athlete or marathoner, it is usually a liability that limits the fraction of VO2max they can sustain at threshold. Different profiles need different training, and you cannot build that distinction into a plan if you cannot see it.
Why one test is limited and why that is not an argument against testing
The skeptics are right that a single lactate test is a snapshot. A snapshot confirms where an athlete is today. It does not prove your coaching is working.
The answer is not to skip testing. It is to test repeatedly.
A realistic rhythm for most athletes is two to four tests a year. A baseline at the start of a macrocycle, a check after the base phase, an optional mid-season assessment, and a closing test at the end of the season. Over multiple tests, you are no longer looking at a static snapshot. You are tracking whether the curve is shifting to the right, whether the gap between LT1 and LT2 is widening, and whether your aerobic-focused block actually moved LT1 the way you intended.
This is where the coaching case becomes hard to argue against. You can show the athlete a measurable shift in their physiology, not a feeling. A rider whose LT2 moved from 260W to 280W over twelve weeks has objectively improved. A runner whose aerobic threshold moved from 5:30/km to 5:10/km has a stronger engine, even if their race times have not caught up yet.
Athletes respond to this. They stay in the program longer, trust the process during the blocks that feel like slow progress, and refer other athletes when they can explain in concrete terms what their coach actually changed.
The practical setup question
The logistics are where a lot of coaches stall. You have roughly three paths.
Send the athlete to a sports lab. Cleanest data if the lab is good, but expect variable quality. Before you refer an athlete, confirm the lab uses stage lengths of at least four to five minutes, lets the athlete use their own bike or power meter where possible, and runs the test on a modality that matches the sport. Cycling data does not translate cleanly to running, and a treadmill test in running shoes is not interchangeable with an outdoor track test.
Buy your own lactate meter. A consumer model like the Lactate Pro 2 or Lactate Scout runs a few hundred euros, with strips around 2 to 3 euros each. If you coach more than a handful of serious athletes, this pays back quickly. It also gives you control over the protocol and the ability to test in the field, on the athlete’s own bike or shoes, in conditions close to their actual training.
Combine the two. Use a lab for baseline and end-of-season assessments, then run your own field tests mid-block to check progress without the full lab cost.
The choice depends on your athlete mix. For a coach working mostly with age-group triathletes and competitive amateurs, owning a meter is usually the better long-term investment.
Where the data lives matters
Running tests is one thing. Making the data useful in daily training is another. Many coaches have a drawer full of PDF reports that never make it into the athlete’s actual plan.
This is where software matters. In Coachbox, you can enter lactate test results directly, generate individualized zones from the aerobe and anaerobic thresholds, and have those zones drive every workout you prescribe. When the athlete trains with a heart rate monitor or power meter, you can see whether they actually hit the zones you intended, not just the pace or power targets.
More importantly, when you run a second or third test over a season, Coachbox lets you overlay the curves. You see the shift visually, compare block to block, and build a physiological dossier that lives alongside the training data. That is what turns testing from a billable one-off into a core part of how you coach.
The real argument
Lactate testing is worth using in coaching because it does three things nothing else does simultaneously. It replaces formula-based zones with physiologically accurate ones. It reveals athlete profiles and limiters that pace and heart rate alone cannot show. And repeated over a season, it produces the kind of concrete evidence of progress that keeps athletes in your program and justifies what you charge.
The coaches who treat lactate testing as optional tend to describe themselves as experience-based. The coaches who integrate it tend to describe themselves as evidence-based. Both can be good coaches. But in a market where athletes increasingly expect data, the second group has an argument that the first group does not.
Want to grow your craft as a coach? The Coachbox Academy offers practical courses on training methodology, data analysis, and coaching in endurance sports.