How do you define lactate threshold?

There is an incredible amount of confusion in both colloquial conversation as well as in the published literature about what lactate threshold (LT) is. In fact, a quick Pubmed search of the term will produce over 20 different definitions from a variety of sources. Even though well-intending researchers, coaches, and athletes are frequently talking about the same thing, this inability (or sometimes unwillingness) to clearly define and agree upon terms can be very confusing. At BSX we have worked hard to clarify the definitions in such a way that are understandable, identifiable, and actionable.

In a broad sense we use the term lactate threshold to refer to two different yet equally important physiologic events. Your BSXinsight device measures both of them for you at the same time so we’ll define each in turn.

LT1 – Aerobic Threshold
Technically speaking, aerobic threshold is the training intensity which produces the first rise of blood lactate above baseline. This event is sometimes referred to as the ‘breakpoint threshold.’

Aerobic threshold is important in training because it is the level of intensity at which anaerobic energy pathways start to become a significant contributor to energy production. In contrast, intensities below this are predominantly aerobic.

Large training volumes at or below this intensity are meant to target development of the aerobic energy producing systems. Endurance athletes want to increase their aerobic threshold because doing so will enable them to train and/or race faster for longer before they begin to rely on anaerobic metabolism which cannot be sustained for very long.

LT2 – Anaerobic Threshold

Technically speaking, anaerobic threshold correlates closer with the onset of blood lactate accumulation or in other words the transition from “steady” to “rapidly increasing” lactate workloads.  You are said to have crossed lactate threshold when blood lactate concentration increases by at least 1 mmol/L in two consecutive stages.

Put more simply, it is defined as the level of training intensity at which lactic acid is produced faster than your body can clear it. Exercise at or above this point is meant to train the complement anaerobic systems.

Anaerobic threshold has historically been one of great focus in endurance athletes because of its close relationship with maximum lactate steady state (MLSS) and ultimately race performance.  In practice, it refers to the highest workload that can be maintained for an extended period of time (45-60min). It is essentially your body’s redline, and is an extremely reliable and powerful predictor of performance in endurance athletes.

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