Brooks, G. A. (1985). Anaerobic threshold: Review of the concepts and directions for future research. Medicine and Science in Sports and Exercise, 17, 22-34.

The amount of lactate in the blood is not an indication of how much anaerobic work has been completed in exercise. It is a result of: (a) processes that produce and contribute to its appearance, and (b) processes which catabolize it after its removal from the blood. "Consequently, the concentration of lactate in the blood provides minimal information" about its rate of production.

Lactate is produced in active skeletal muscle and other sites not directly involved with physical exercise (e.g., brain function, inactive muscles). All its accumulation shows is that there has been an increased metabolic rate and glycolytic carbon flow. Lactate accumulation is influenced by the following factors.

1. The maximum volume of lactic dehydrogenase (LDH), which is several times greater than the combined activities of enzymes which provide alternative pathways of pyruvate metabolism.
2. The Km of LDH for pyruvate, which is sufficiently low to assure maximal stimulation of LDH in the conversion of pyruvate to lactate.

3. The Keq of pyruvate to lactate conversion which exceeds 1000.

Lactate production occurs in muscle for reasons other than an oxygen limitation on mitochondrial ATP production. Also, parameters associated with ventilatory threshold, an often quoted closely related phenomenon of anaerobic threshold, do not always track changes in blood lactate concentration.

Implication. The popular reliance on the anaerobic threshold as a major training determinant is partly flawed, and therefore unreliable, because of its incomplete and erroneous conceptualization.

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