Ventilatory threshold

Ventilatory threshold is the exercise intensity at which ventilation starts to rise out of proportion to oxygen uptake, alongside an abrupt rise in blood lactate.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 134.} Breathing initially increases mainly through deeper breaths; beyond this point, breathing frequency takes over.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 134.} This happens above roughly 45% to 65% of VO2 max in untrained people and 70% to 90% in trained clients.^{1Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 134.} Ventilatory threshold corresponds well with lactate threshold.^{2Haff and Triplett (eds.), Essentials of Strength Training and Conditioning, 4th ed., p. 66.}

Coaching sources commonly describe two thresholds, VT1 and VT2.^{3Viada, The Ultimate Hybrid Athlete, p. 138.},^{4Viada, The Ultimate Hybrid Athlete, p. 139.} At VT1, deeper breaths alone can no longer keep up, breathing rate rises and conversation becomes difficult.^{3Viada, The Ultimate Hybrid Athlete, p. 138.},^{4Viada, The Ultimate Hybrid Athlete, p. 139.} At VT2, breathing can no longer keep carbon dioxide levels stable.^{4Viada, The Ultimate Hybrid Athlete, p. 139.} Viada describes it as the point above which fatigue builds quickly, while IPTA describes it as the onset of blood lactate accumulation.^{4Viada, The Ultimate Hybrid Athlete, p. 139.},^{5International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 193.}

In practice

• Lab testing measures expired gases during a maximal exercise test.^{6Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 201.}
• ACSM considers the talk test a reasonable field substitute for identifying ventilatory threshold.^{7Ozemek et al., ACSM’s Guidelines for Exercise Testing and Prescription, 12th ed., p. 347.}
• Viada uses VT1 as the upper limit of zone 2 training, favoring the ventilatory threshold test for its combination of simplicity and accuracy.^{8Viada, The Ultimate Hybrid Athlete, p. 137.}
• IPTA treats heart rate at VT1 as the boundary between purely aerobic conditioning and the start of anaerobic conditioning.^{9International Personal Trainer Academy, Certified Personal Trainer Textbook, p. 194.}