Lactate threshold

Lactate threshold is an exercise intensity above which blood lactate rises more rapidly than it can be cleared. It marks a transition in the balance between lactate production and removal, not a sudden switch to anaerobic metabolism.

Blood lactate: Lactate concentration measured in blood, commonly used to track metabolic responses to exercise. Its rise during progressively harder exercise is the measurable signal used to identify the threshold.
Lactate threshold training: Endurance training performed near or around an athlete’s lactate threshold. Training near this intensity aims to improve the pace or power sustainable before rapid lactate accumulation.
Lactate turnpoint: A point during incremental exercise where blood lactate begins a sustained, marked increase. It is a related threshold concept, but its operational definition may differ from other lactate markers.
Blood lactate sampling: The collection and analysis of blood samples to measure lactate concentration. Sampling site, timing, and measurement method can shift an estimated threshold.
Lactate shuttle: The movement of lactate between and within tissues, where it can be oxidized or used to support metabolism. Lactate can be transported and reused, so its accumulation reflects an imbalance rather than waste buildup alone.
Lactate threshold test: An exercise test that estimates lactate-related intensity transitions, often through staged workloads and blood sampling. Protocol and sampling choices affect the threshold value obtained.
Onset of blood lactate accumulation: A fixed blood lactate concentration used as a standardized marker during incremental exercise testing. This fixed-value method is not identical to locating the intensity where lactate begins rising rapidly.
Incremental exercise test: An exercise test in which workload rises in stages or continuously until a target or limit is reached. Stage duration and workload increments influence the blood lactate curve used to estimate threshold.
Monocarboxylate transporter: A membrane protein that transports lactate and other monocarboxylates across cell membranes. Transport between muscle fibers and blood helps determine how quickly lactate appears and disappears.
Critical power: The highest constant exercise power that can be sustained without a continuing decline in muscle energy reserves. It provides a distinct performance boundary that can be compared with lactate-based estimates.

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