What is a Lactate Threshold Test?

Written by: Karly Mendez-Huebel, Human Performance Specialist at Memorial Hermann IRONMAN Sports Medicine Institute

You may have heard the terms “Lactic acid or lactate threshold” before and may have used them yourself. Many athletes refer to lactic acid as the burn they experience in their legs while exercising and consider lactic acid to be a harmful byproduct in the body. This is a misconception and a lactate threshold test is designed to help you understand your bodies unique lactate response and how to train to meet your specific goals. Lactate threshold tests are most appropriate for endurance athletes and is a tool that can be utilized by athletes and coaches to train smarter, not harder.

What is Lactate?

Lactate is the byproduct of glucose or fuel utilization by muscle cells. The more glucose released in the cell, the higher the lactate production (usually, higher lactate production is seen in higher intensity exercise because of higher glucose usage). A study by Peake and Colleagues demonstrates that high intensity interval training will have higher heart rates that correspond to higher blood lactate concentrations, increased oxygen use, and increased carbohydrate use which leads to higher respiratory exchange ratios when compared to moderate intensity training. The energy required to move is supplied from the breakdown of ATP (adenosine triphosphate). When your body demands energy faster than your aerobic system can produce it, your glycolytic energy system (anaerobic) picks up the slack. Your body must then clear the lactate in the blood/muscles and utilize it for fuels. In other words, as exercise increases, the increased production of lactate outpaces the body’s ability to clear and utilize it, making the level of lactate in the blood/muscles rise.

Lactate Threshold Testing

Lactate threshold is the point during exercise where lactate builds up in the blood faster than the body can remove it, meaning the athlete can no longer maintain steady state (aerobic base). Your lactate threshold defines the upper limit of your sustainable efforts in training. Once you cross over and rely more heavily on your glycolytic system for energy, you are exercising on borrowed time. The accumulation of blood lactate will hinder your muscles’ ability to contract, and you will be forced to slow down and/or stop (the more work you can do before reaching lactate threshold, the better). But it’s important for athletes to understand that your lactate threshold can be shifted with planned training. The goal is to help you expand your aerobic base and ultimately run faster with less effort.

Lactate threshold testing can be utilized to find the appropriate training intensity for athletes and help them shift their curve. A lactate threshold test is like a VO2max test, except the duration of each workload is a bit longer. During the test, several blood samples are taken from finger sticks to obtain the blood lactate levels at a variety of paces (this is not a maximal effort test like a VO2max but does require an intense workload). Your initial lactate threshold test provides a starting point and specific pace and heart rate zones to train at to become a more efficient runner.

Once you have your lactate threshold pace and heart rate we can then implement the 80/20 rule. You will be encouraged to implement 80% steady state aerobic workouts to place the appropriate load on the aerobic system and build the system up appropriately. The remaining 20% of your workouts can he hard, and high intensity allowing your body to make lactate and learn to clear it out. Over time, with lactate threshold training, the body learns to contract muscles quickly with less buildup of lactate in the blood. If the muscles can increase workloads/stress while maintaining a faster pace at aerobic levels, you save muscle glycogen usage while (at the same time) decreasing the amount of blood lactate being produced. Ultimately leading you to higher performance.