Lactate threshold

Lactate threshold (LT) is the exercise intensity at which blood lactate begins an abrupt rise above baseline.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 66.} It marks much greater reliance on anaerobic energy production and aligns well with the ventilatory threshold; both are often used as markers of the “anaerobic threshold.”^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 66.} In untrained clients, LT typically occurs at 50% to 60% of VO2 max, compared with 70% to 80% in aerobically trained athletes.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 66.} A second break in the curve, the onset of blood lactate accumulation (OBLA), occurs at a higher intensity, near 4 mmol/L.^{2Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 46.}

LT determines how much of a client’s VO2 max they can sustain: two clients with a VO2 max of 50 mL/kg/min differ by 5 mL/kg/min in sustainable output if their thresholds sit at 80% and 70%.^{3Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 142.}

In practice

• Training near or above LT or OBLA shifts both to higher intensities, largely through more mitochondria.^{2Schoenfeld and Snarr (eds.), NSCA’s Essentials of Personal Training, 3rd ed., p. 46.}
• Daniels prescribes threshold runs at a “comfortably hard” pace that a rested runner could race at for about 60 minutes.^{4Daniels, Daniels’ Running Formula, 4th ed., p. 91.},^{5Daniels, Daniels’ Running Formula, 4th ed., p. 92.} Options include a steady 20-minute tempo run or cruise intervals with short rests.^{4Daniels, Daniels’ Running Formula, 4th ed., p. 91.},^{5Daniels, Daniels’ Running Formula, 4th ed., p. 92.} He limits threshold running in one session to 10% of weekly mileage.^{5Daniels, Daniels’ Running Formula, 4th ed., p. 92.}
• Zones based on estimated maximum heart rate don’t locate a client’s LT; the NSCA holds that an effective endurance program needs some knowledge of it.^{6Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 579.}

Where sources differ

NSCA textbooks use LT for the first rise above baseline and call the 4 mmol/L point OBLA.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 66.} Viada uses lactate threshold, anaerobic threshold and maximum lactate steady state for the second, higher threshold, his VT2.^{7Viada, The Ultimate Hybrid Athlete, p. 139.} Just above that point, lactate accumulates and fatigue builds quickly.^{7Viada, The Ultimate Hybrid Athlete, p. 139.} He notes that the terms describe slightly different things, mostly measured in different ways.^{7Viada, The Ultimate Hybrid Athlete, p. 139.}