Previously we talked about VO2max and why it isn’t the best (or really a good) indicator of performance in endurance athletes. But what would be a good indicator? Over the last several years, lactate threshold (LT) has been a pretty consistent indicator of performance in most endurance-related sports.
Let’s talk about what LT is. Your LT is the point at which your body produces more lactic acid than it can recycle back into new energy. Previously, it was thought that excessive blood lactate was what caused fatigue and muscle soreness. While this has since been discredited, lactate levels in the blood are a good indicator of other things that do cause fatigue. So why do we look at LT? High lactate levels correlate with other exercise byproducts that cause fatigue, and when the amount of lactate in the blood is increasing faster than the body can recycle it, there is also an increase in the byproducts that cause fatigue. This breaking point is generally regarded as the effort an athlete can sustain for 60 minutes. For example, if your bike LT is 250 Watts, you are capable of pushing 250 Watts for an hour time trial.
Why is this a better indicator of performance than VO2max? Mainly, VO2max is not quantifiable enough to be a good performance indicator. The amount of time someone can hold a VO2max effort can vary substantially between individual athletes, while LT is almost always the effort an athlete can hold for about an hour.
So how does an athlete train to increase LT? There are a couple of ways, but the most effective method is doing a lot of intervals. Just like every other aspect of exercise, LT follows the “overload and adapt” principle, meaning that in order to increase LT, you need to do work above that workload. Doing lots of sustained intervals (5 minutes on the bike, mile repeats on the track, 400m repeats in the pool, etc.) at efforts just above your LT will allow your body to adapt to working at that higher capacity and increase your LT. For example, if your bike LT is 250W, doing intervals just above that from 250-300W or so will allow your body to increase the ability to process that excess blood lactate.
So to recap, LT is the point at which your body produces lactate faster than it can recycle it. While lactate does not cause fatigue, it does correlate with exercise byproducts that do. LT tends to be a better indicator of performance in endurance sports since it is a more quantifiable measurement than VO2max. Finally in order to increase your LT, doing lots of interval work above LT will surely do that!