Lactate threshold is the specific level of effort or pace at which fatigue accelerates. For experienced runners, this usually happens at around 90% of their maximum heart rate, which corresponds to a pace between their 10 km and half marathon race pace. For less experienced runners, lactate threshold is often below 90% of maximum heart rate.
Certain Garmin devices can detect your lactate threshold either through a guided test or automatically during a normal run. In both cases, the device collects heart rate data across different pace ranges and estimates your lactate threshold as both a running pace and a heart rate in beats per minute. For the best results, and so the device can accurately learn your overall fitness, it is highly recommended to complete several runs after first setting up your watch. Once the device has got to know you well, subsequent lactate threshold results will be more accurate than they may have been initially.
In the past, athletes who wanted to use their lactate threshold to personalise their training had to undergo blood tests to estimate the amount of lactate accumulating during exercise. Because of this process, only a limited number of athletes had access to this valuable training information.
The Firstbeat lactate threshold detection method used in Garmin devices is based on the fact that breathing rate can be detected through heart rate variability (HRV) analysis. Inhaling and exhaling cause small changes in the intervals between heartbeats (HRV). When these variations are decoded and combined with other performance data, the device can detect simultaneous changes in heart rate and signal when your performance level is above your lactate threshold.
How does this help you? Lactate threshold is the best indicator of your endurance capacity. As your ability to cover long distances at a faster pace grows, you will also see your lactate threshold rise. This metric is also a valuable tool because it helps you identify your personal training zones and thereby improve your personal performance. That is because it lets you base your training on the actual development of your body's physiological condition, rather than on arbitrary percentages of maximum heart rate.
Knowing your lactate threshold allows you to train more purposefully. Many coaches also include a certain amount of lactate threshold-based running in an overall training programme. The lactate threshold feature on compatible Garmin devices helps you determine your lactate threshold without having to pay for an expensive lab test with multiple blood samples.
