lactate threshold

Intensity of exercise above which lactate accumulates increasingly in the blood; traditionally ascribed to shortfall in oxygen supply to muscles, requiring some energy to be supplied by anaerobic metabolism — hence also known as ‘anaerobic threshold’. Recent research challenges this; lactate can be produced by fully-oxygenated muscles, as a result of processes driving the oxidative processes faster. Only above the maximal rate of oxygen uptake does lactate accumulation unequivocally indicate that significant energy is being supplied anaerobically.

— Neil Spurway

See also breathing during exercise; exercise; fatigue; metabolism.

The point during exercise of increasing intensity at which blood lactate begins to accumulate significantly above resting levels. There are several different methods of estimating the threshold. They include specifying a given value of blood lactate (usually between 2.0 and 4.0 mmol lactate l⁻¹) and using this value as a common reference point (known as Onset of Blood Lactate Accumulation or OBLA). Another method identifies graphically the onset of an exponential increase in lactate concentration. The assumption that the lactate threshold represents the anaerobic threshold has been challenged recently, but the lactate threshold is generally accepted as being useful in identifying a specific intensity of exercise below which endurance is mainly a function of fuel supply, body temperature, or soft tissue trauma, and above which there is a significant reduction in endurance, probably due to metabolic disorders such as acidosis. Appropriate training (e.g. regular intensive aerobic activity) can enable an athlete to postpone lactate accumulation until higher intensities of exercise are reached. This is beneficial to an endurance athlete because lactate formation contributes to fatigue.