A comparative evaluation of the individual anaerobic threshold and the critical power

The individual anaerobic threshold (IAT) is defined as the highest metabolic rate where blood lactate (La) concentrations are maintained at a steady-state during prolonged exercise. The asymptote of the hyperbolic relationship between power output and time to fatigue has been defined as the critical...

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Bibliographic Details
Published in:Medicine and science in sports and exercise 1992-05, Vol.24 (5), p.543-550
Main Authors: MCLELLAN, T. M, CHEUNG, K. S. Y
Format: Article
Language:English
Subjects:
Adult
Anaerobic Threshold - physiology
Biological and medical sciences
Energy Metabolism - physiology
Exercise - physiology
Exercise Test
Fundamental and applied biological sciences. Psychology
Humans
Hydrogen-Ion Concentration
Lactates - blood
Male
Pulmonary Gas Exchange - physiology
Space life sciences
Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports
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Summary:The individual anaerobic threshold (IAT) is defined as the highest metabolic rate where blood lactate (La) concentrations are maintained at a steady-state during prolonged exercise. The asymptote of the hyperbolic relationship between power output and time to fatigue has been defined as the critical power (CP), which, in theory, represents the highest metabolic rate where a steady-state response can be achieved during prolonged exercise. Since IAT and CP may define the same power output, the purpose of this study was to compare the gas exchange, blood La, and acid-base responses during exercise at the metabolic rates defined as IAT and CP. Fourteen males performed a maximal incremental cycle exercise test that was followed by a light active recovery period to determine IAT. Subsequently, subjects exercised to fatigue at five power outputs (calculated to elicit from 90% to 110% VO2max) to determine CP. IAT occurred at a significantly lower power output and VO2 (235 +/- 44 W and 2.97 +/- 0.47 l.min-1, respectively) compared with CP (265 +/- 39 W and 3.35 +/- 0.41 l.min-1, respectively). During 30 min of exercise at IAT, blood La levels increased during the initial 10 min to 3.9 +/- 1.9 mmol.l-1 but did not change during the final 15 min. Blood pH decreased to 7.32 +/- 0.04 at 5 min and did not change thereafter, while PCO2 fell from 41.5 +/- 3.2 mm Hg at 5 min to 36.2 +/- 3.6 mm Hg at 30 min. Only one subject completed 30 min of exercise at CP.
ISSN:0195-9131
1530-0315
DOI:10.1249/00005768-199205000-00008