Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

Increasing exercise intensities will induce an increase in glycolytic flux. High glycolytic activity is associated with reduced fat oxidation rates and increased accumulation of lactate. Both lactate and hydrogen ions have been shown to be directly related to the decreased fat oxidation rates. The aim of the present study was to determine whether the exercise intensity at which maximal fat oxidation rates occur coincides with the intensity at which lactate starts to accumulate in plasma. Thirty-three moderately trained endurance athletes performed a graded exercise test to exhaustion on a cycle-ergometer with 35 W increments every three minutes. Expired gas analysis was performed throughout the test and stoichiometric equations were used to calculate fat oxidation rates. The intensity which elicited maximal fat oxidation (Fat (max)) and the intensity at which fat oxidation rates became negligible (Fat (min)) were determined. Blood samples for lactate analysis were collected at the end of each stage of the graded exercise test. The intensity at which lactate concentration increased above baseline (LIAB) and the lactate threshold (LT-D) were determined (D-max method). Fat (max) was located at 63 +/- 9 % V.O (2)max and LIAB at 61 +/- 5 % V.O (2)max and there appeared to be no statistical difference between the two intensities. Fat (max) and LIAB were significantly correlated. Fat (min) and LT-D were also significantly correlated but were located at different intensities (82 +/- 7 and 87 +/- 9 % V.O (2)max respectively). The data of the present study showed that accumulation of lactate in plasma is strongly correlated to the reduction seen in fatty acid oxidation with increasing exercise intensities. The first rise of lactate concentration occurred at the same intensity as the intensity which elicited maximal fat oxidation rates.

Original publication




Journal article


Int j sports med

Publication Date





32 - 37


Adult, Bicycling, Calorimetry, Indirect, Energy Metabolism, Exercise, Humans, Lactates, Lipid Metabolism, Oxidation-Reduction, Oxygen Consumption