The Toolbox: How To Assess Lactate Threshold
Ed. Note—it's January, and our series on setting yourself up for the best triathlon season yet rolls on. We're calling this series "The Toolbox," and throughout the year we'll invite guest bloggers, athletes, and coaches to help you get faster, happier, and smarter. Today we stop over with Jesse Kropelnicki, head coach at QT2systems and coach of many top-level pros such as Linsey Corbin and Lenny Ramsey. Jesse walks us through the different types of fitness assessments you might employ to start off this 2021 season.
Over the years, several tests and concepts have been developed and used by coaches and physiologists to determine an athlete's lactate threshold and, by extension, what type of training will best stimulate that athlete's development. Every athlete's physiology is unique, so finding out how they will best respond to training is a crucial step for any coach. "One size fits all" methods simply don't cut it, here. Today we'll look at different ways of determining an athlete's lactate threshold, and what your results might mean to you.
First of all, though, what's "lactate threshold" in the first place? Much ink (or, more appropriately, many pixels) has been spilled in defining this term, so we'll do our best to keep it simple. First of all, lactate threshold is interchangeable with several other terms you may have seen: FTP, rFTP, Threshold Pace, Anaerobic Threshold, Maximum Lactate Steady State (MLSS), Onset of Blood Lactate Accumulation (OBLA)...they all essentially mean the same thing. All these terms refer to the range of intensity where you begin to make more lactate in your working muscles than your system can clear away. The word threshold is apt, since it denotes a separation between two rooms. One side of the separation is manageable, sustainable effort—something you could keep up for hours. On the other side of the separation is effort that is not sustainable—something you could keep up for only minutes.
In most cases, very aerobic athletes will respond best to more anaerobic training (if their peripheral system can handle it) and visa-versa. The purpose of this writing is to show you the most common concepts and charts—all pretty much showing the same thing or concept! Many coaches and athletes get confused with the various testing methods and concepts and don’t realize it’s all trying to show/determine the same thing for the most part! In the charts below I show the theoretical difference between a more aerobic athlete (black line) and more anaerobic athlete (red line).
Blood Lactate Ramp Test
Blood lactate testing can be performed at an exercise physiology lab, or by yourself using a device such as Lactate Pro. These devices are available online and (with practice), are fairly easy to use. Most lab-based testing protocols include some type of ramp up effort, using discrete intervals with either running or cycling. For example, a test where the athlete increases his/her effort 20 watts every three minutes on a cycling ergometer until exhaustion is a popular protocol. This can be replicated for running on a track or treadmill where pace is increased at discrete increments until exhaustion. The tester takes a blood lactate reading at the end of each interval, and plots those lactate values against wattage if cycling or pace if running. A plotting of this data can then be used to determine the athlete’s lactate threshold, as well as the athlete’s specifics (i.e., are they aerobically efficient, do they lack power or pace at above TH, etc). A commonly used definition for the workload at which threshold occurs, is the workload where blood lactate has already increased by 1 mmol from baseline, and then increases 1 mmol more in a single test step (known as the Thoden method). This information can then be used in designing the athlete’s specific training program. For example, if an athlete is not aerobically efficient, the coach may prescribe a longer period of aerobic training while designing the season periodization. The three key points on this curve are the highest lactate/power achieved, the power at threshold, and the power at the first uptick in lactate. These three points can tell you a lot about where the athlete may need more work for their specific race distance.
As a coach, the exact protocol that you use for lactate testing is completely up to you! There are many protocols out there, but as long as you know and understand how to operate and interpret your protocol, the results will be useful. The idea is to maintain intra-athlete consistency by always using the same protocol for an individual.
Heartrate Ramp Test
This test requires a heart rate monitor and a cycling ergometer, such as a Wahoo Kickr or other smart trainer. A GPS unit is needed if doing a run-based test. The athlete begins by riding at a purely aerobic intensity/power. Every 1-3 minutes, the athlete will increase his or her power by some pre-defined interval of 10-20w. This continues until the athlete can no longer complete the stage. Generally speaking, the interval length, wattage increase, and starting wattage should be set up to have the test last about 15-20 minutes. The recorded points should then be plotted on a graph with heart rate on one axis, and wattage/load on the other. The graph’s deflection point will typically indicate the athlete’s aerobic threshold. The heart rate will generally increase linearly, up until the deflection point, where the heart rate reaches TH. At that point the heart rate will generally deflect to a much more shallow slope. More aerobic athletes will deflect more dramatically than the anaerobic athletes, and therefore the ability to determine TH using this method exclusively can sometimes be impossible. For the more anaerobic athletes, the line will continue past threshold. In those cases where athletes may show no clear deflection it requires the coach, athlete, and/or physiologist to use his or her knowledge of the athlete or other parallel tests to determine the threshold value.
Power based testing on the bike is a fantastic way to determine an athlete’s specific training needs versus the event distance and competition needs they are preparing for. As an example, a short course, draft legal triathlete requires higher maximum power output relative to their aerobic power. Power profiling allows the coach to understand this relationship and provide training that meets the needs identified in the power profile, relative to the requirements of the goal events. Power profiling is done by having the athlete do successive time trials to determine their power output over various durations. Typically done on different days, the athlete may do 5 second, 1 minute, 5 minute, and 60 minute tests. These durations are chosen as those best reflecting neuromuscular power, anaerobic capacity, maximal oxygen uptake (VO2max), and lactate threshold (LT), respectively. This does not mean to imply that a 1 minute all-out effort is completely anaerobic (in fact, roughly 40-45% of the energy during such exercise is derived aerobically) or fully utilizes anaerobic capacity (which generally requires 1.5-2.5 min to deplete), or that a 5 minute all-out effort entails exercising at precisely 100% of VO2max. Rather, power output over these target durations would simply be expected to correlate well with more direct measurements of these different physiological abilities. Secondarily, the index efforts were chosen in an attempt to increase reproducibility (e.g., use of 5s vs. 1s power, as an indicator of neuromuscular power), and for convenience. The coach knows the relationship of these values to one another for the average athlete and compares this to the test. Based upon how this relationship compares to the average, the coach may gain insight into areas of the athlete’s relative strengths and weaknesses in the context of the needs for their race. My opinion is that the shorter testing intervals, the more relevant for pure cyclists and draft legal triathlon, whereas most long course triathletes have much more aerobic energy requirements, and therefore a testing protocol of 3 minute, 20 minute, and 60 minute tests may be more useful. Using longer intervals for your tests as a long course athlete more accurately measures the likely energy systems an athlete may require for race day.
One such power profiling test is the 3 minute | 20 minute test. This test is practical because it can be completed in a single day and proctored remotely. After a proper warm-up, the athlete completes a 3 minute all out time trial, while recording average power, then rests for 10 minutes and completes a 20 minute all out time trial, while recording average power. The ratio of these values can help create a very simple power profile indicating the athlete’s training needs. After completing many of these tests, the average ratio will become evident. It should also be noted that power or pace should not drop by more than about 5% during the test, otherwise the test is invalidated and should be repeated on another day.
The metabolic test is administered as a ramp test similar to many of the tests above. The metabolic test utilizes your breathing via a mouth piece and nose clip as your effort increases and is able to measure the percentage of energy use from fat and from carbohydrate. Because carbohydrate is the primary fuel source for anaerobic energy production, and fat for aerobic energy production, this test can be a good indicator of your particular energy system usages (how aerobic or anaerobic you are). Again, this information helps inform the training. (Ed. Note: if you're interested in this style of training, check out another article by Bevan McKinnon on metabolic efficiency, here)
This type of assessment has become popular through the advent of INSCYD, a German company that provides remote metabolic testing through only the use of a power meter. Athletes determine their lactate threshold and something called their "VLamax," which identifies the rate at which a particular athlete generates lactate. More anaerobic athletes (such as short course triathletes and sprinters in cycling) make more lactate and make it faster, whereas more aerobic athletes (70.3 and Iron-distance) tend to make lactate slower.
The fatigue index concept defines how much an athlete’s performance declines every time the distance is doubled. There is no distinct test to test this directly, but rather a concept that you can help understand with athletes as they race. Everyone knows they may race well at long course versus short course or visa-versa; fatigue index helps define that concept. Many popular tests help capture this information: swim 200 meters as fast as you can, and then 400 meters a few minutes later. Tracking the rate by which you "decouple" or slow down can give you insight into what kind of athlete you are. You can create the same kind of effort on the track by running 800m and then 1600m. If you slow down a lot between the 800 and 1600, but your 800 is relatively fast, you may be more anaerobic. Slow down only a little, but don't really display a scorching 800m? Well, you may be more aerobic. Don't despair! Being more aerobic will help you in longer events, but this kind of test simply shows you where your weaknesses are, and what you might be able to do about them!
At the end of the day, all of these concepts and methods capture similar and corresponding information. Any one of them can provide a tremendous amount of insight, to the coach, about his or her athlete(s). Used in conjunction with one another, they can help to unlock the athlete's true potential, by further refining and personalizing the most appropriate methodologies for any given athlete.