Written by: Tim Mickleborough
Is there an accurate do-it-yourself method I can use to determine my lactate threshold for cycling and/or running using a power meter or GPS device?
In order to track fitness changes during the season it is important to conduct regular physiological testing. Access to a human performance laboratory is optimal and can yield important information, such as power and heart rate (for cycling) and pace and heart rate (for running) at the lactate threshold.
It is important to understand what lactate and the lactate threshold (LT) are before we proceed with the different types of tests available to the athlete for determining LT. The blood lactate level measured at rest or at any point during exercise represents a balance between its rate of production and release into blood and its subsequent removal from the bloodstream. This balance is referred to as the lactate turnover rate, and it determines the baseline lactate concentration in the blood. An untrained individual will typically have a blood lactate level of 4 to 15 mg/dl (0.44 to 1.7 mmol/L). On the other hand, trained endurance athletes typically have a lactate level of around 3 to 5 mg/dl (0.3 to 0.6 mmol/L).
However, a hard training session or a period of overtraining can elevate these levels in athletes.
There exists an effort level termed the maximal lactate steady state (MLSS), which an athlete can continue to work at for an hour or even longer. If an athlete maintains this effort level, his or her blood lactate level will remain relatively stable. However, even a small increase in effort level above the MLSS can elevate an athlete’s blood lactate and eventually force him or her to stop. (This could occur anywhere from a couple of minutes to 30 minutes into a workout depending on the effort level above the MLSS.) It is important to note that above the MLSS there are no more steady states, just the inevitable progression to exhaustion. This effort level above the MLSS has a few names, but the most common are the LT, the anaerobic threshold or the onset of blood lactate accumulation (OBLA). Both the MLSS and LT are the best indicators of endurance performance. In fact, power output at LT is the best predictor of performance at race distances from a few minutes to several hours. Therefore, improvements in either the MLSS or LT are almost always accompanied by improvements in race performance. Frequent LT testing (every four to six weeks) is usually the best indicator of potential race performance for endurance events. Endurance training shifts the LT to a higher percentage of VO2 max (maximal oxygen consumption).
In the laboratory, the LT can be assessed by indirect calorimetry, using increasing exercise workloads (on a cycle ergometer or treadmill) to study ventilation and gas exchange and correlate the LT to a particular heart rate and/or power output, or a certain percentage of these quantities. However, not all athletes have access to a human performance laboratory. So can athletes determine their cycling and running AT without having to visit a human performance laboratory?
The answer is yes—but how do we determine this elusive LT during a field test? Portable lactate analyzers are becoming cheaper, but let’s assume that an athlete does not have a portable lactate analyzer.
With regard to cycling, researchers showed two decades ago that LT is highly correlated with one-hour maximal cycling power,1 and with regard to running, another study proved that a 10K flat run performed at a high effort level will get you close to MLSS and LT.2 However, both of these field tests require an athlete to have a power meter for the bike and a GPS tracking/accelerometer device (e.g. Garmin) for the run. Using these devices to determine cycling and running LT has been described well in a variety of very good training books.3,4,5,6 No matter how you choose to test yourself, the most important aspect is to be consistent between tests. Perform the test in exactly the same manner each time and on the same indoor trainer or course and under the same environmental conditions.
Determining LT with a Power Meter
The LT is significantly correlated to one-hour maximal cycling power output.1 Does this mean that you have to ride for one hour for your LT test? The answer is no—one method is to determine your critical power at LT,3 and the other is to determine your functional threshold power (FTP) at LT.5 Critical power and FTP at LT are essentially the same thing. Critical power is a method of comparing work capacity for different periods of time in order to determine the power an athlete can maintain for a long time. To determine one’s critical power, an athlete performs an all-out interval lasting three minutes. On the following day, the athlete will perform an all-out interval lasting 20 minutes. He or she can then calculate critical power using the data from those two intervals. For example, let’s assume that the athlete managed an average of 350 watts (W) for the three-minute test and 250W for the 20-minute test. To calculate critical power, you multiply the average power by the number of seconds in the interval (350W x 180 seconds (sec) = 63,000 joules for the short interval; 250W x 1200 sec = 300,000 joules for the long interval). Now divide the difference in joules [(300,000-63,000) / (1200-180) = 232.4 W] to find the critical power at LT.3, 5
An alternative is to determine your FTP, also known as CP60, which is the power you can maintain for one hour. The easiest way to determine your FTP is to do a 20- or 30-minute time trial in which you put out a strong, steady effort for the entire duration. It is important not to go out too hard, as you will not be able to produce your true MLSS; the goal is to produce the highest average watts over the entire period. After you complete the test, download the power data and subtract 5 percent from the average power for the entire 20- or 30-minute test—this is the FTP at LT. Subtracting 5 percent from the average power results in a power value that would be very close to a 60-minute power value5.
For running, there are a variety of methods you can use to determine your running LT with the help of a GPS device. One method is to run a 10K race and determine your average pace (min/mile) and heart rate for the entire race—this will produce a fairly accurate estimation of running LT. An alternate method is to run hard for 20 to 30 minutes on a moderately flat course and again monitor your heart rate and pace. Pay particular attention to your breathing. When it becomes labored for the first time, you have most likely reached your LT. There are additional tests for running that can be performed on a track to determine LT.4
With more athletes now using power meters and GPS devices, the need has clearly arisen for power-based cycling and running-paced training programs similar to those used with heart rate monitors. Software packages such as TrainingPeaks WKO+ (Trainingpeaks.com) and RaceDay Software (Physfarm.com) are excellent desktop analysis software packages for power meters, heart rate monitors and GPS devices, and both programs compute training zones based on power and running pace.
1. Coyle, E.F., A.R. Coggan and M.K. Hopper. (1988). “Determinants of Endurance in Well-Trained Cyclists.” Journal of Applied Physiology 64.6 (1988): 2622-2630.
2. Jones, A. and J. Doust. (1998). “The Validity of the Lactate Minimum Test for the Determination of the Maximal Lactate Steady State.” Medicine & Science in Sports & Exercise 30.8 (1998): 1304-1313.
3. Skiba, P.F. The Triathlete’s Guide to Training with Power. Tinton Falls, NJ: PhysFarm, 2008.
4. Friel, J. The Triathlete’s Training Bible. 3rd Ed. Boulder, CO: VeloPress, 2008.
5. Allen, H. and A. Coggan. Training and Racing with a Power Meter. Boulder, CO: VeloPress, 2006.
6. Friel, J. and G. Byrn. Going Long: Training for Ironman-Distance Triathlons. 2nd Ed. Boulder, CO: VeloPress, 2008.