What is Lactate Threshold?

lactate threshold Jul 27, 2022

What is lactate threshold, and how does it impact our performance?


First, we should have an understanding of what lactate actually is. Simply put, lactate is a byproduct that our bodies produce during exercise. It is formed mostly in muscle cells and red blood cells. When there are low levels of oxygen in our body, we break down carbohydrates to use for energy, and this is when lactate is formed. There are many factors associated with fatigue, and while lactate accumulation is something that is associated with fatigue, it is not lactate in and of itself that causes fatigue. 

First, we need to have an understanding of aerobic versus anaerobic exercise. Aerobic exercise is typically done at less than 70% of an athlete’s max heart rate. These are lower-intensity, longer-duration workouts. Anaerobic exercise is typically done at greater than 70% of an athlete’s max heart rate. These are higher-intensity, shorter-duration workouts. There are differences in adaptations between these two forms of training, and there are major differences when it comes to our lactate levels.

Aerobic exercise is able to clear lactate faster than our body can produce it. Thus, when we are exercising at aerobic intensities, we are not accumulating high levels of lactate. Anaerobic exercise produces lactate faster than our body can clear it. Thus, our lactate levels will accumulate when we are exercising as anaerobic intensities. Furthermore, lactate is utilized by our type I (endurance) muscle fibers, which is how we are able to clear lactate during aerobic exercise faster than we can produce it. However, the important concept to understand is that lactate will accumulate when our production of it exceeds our clearance of it.

Again, while lactate isn’t the sole cause of fatigue, it is strongly associated with it. Higher lactate accumulation has a strong correlation with lower performance at all work intensities. To help visualize this, see below for a chart from a study measuring blood lactate levels in cyclists of all different abilities at varying work intensities.

Differences in blood lactate levels between competitive cyclists of different levels. San Millán et al, 2009

The definition of the “threshold” in lactate threshold is the point at which our bodies switch from primarily utilizing our aerobic system to utilizing our anaerobic system. In other words, it is the point at which our production of lactate begins to exceed our clearance of lactate. This is typically at about 70% of our max heart rate, which has a strong correlation to our VO2 max. For example, a work intensity of 70% of our max heart rate is about the same work intensity of 70% of our VO2 max. The threshold point can be visualized by this chart:


Now, because our VO2 max is adaptable with training and is strongly correlated with our lactate threshold, our lactate threshold is adaptable as well. With appropriate training, we are able to produce less lactate at higher work intensities. However, it is not the threshold point itself that changes. Our lactate threshold will always be ~70% of our max heart rate or our VO2 max, it is just the workload of what 70% is that changes. As we train, we are able to work at higher workloads with less lactate accumulation. The chart below shows a great summary of what this looks like in a trained versus untrained athlete.

Written by Dr. Carmen Scuito, PT, DPT, CSCS


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