Research article - (2019)18, 44 - 51
A Comparison of the Maximal Fat Oxidation Rates of Three Different Time Periods in The Fatmax Stage
Kerem T. Özgünen1,, Çiğdem Özdemir1, Selcen Korkmaz-Eryılmaz2, Abdullah Kılcı2, Özgür Günaştı1, Sanlı S. Kurdak1
1Çukurova University, Medical Faculty, Department of Physiology, Division of Sports Physiology, Adana, Turkey
2Department of Physical Education and Sports, Adana, Turkey

Kerem T. Özgünen
✉ Çukurova University, Medical Faculty, Department of Physiology, Division of Sports Physiology, Adana, Turkey
Email: kozgunen@gmail.com
Received: 19-09-2018 -- Accepted: 30-11-2018
Published (online): 11-02-2019

ABSTRACT

This study aimed to compare the maximal fat oxidation (MFO) rates obtained from the stage average, last 2 min average, and highest value in the Fatmax stage determined with a 6 min step protocol. A total of 35 overweight, sedentary healthy men (age: 25.4 ± 0.7 years, body mass index: 26.0 ± 0.6 kg/m2) participated in the study. Substrate oxidation was calculated using breath-by-breath gas exchange data for each stage. When the change in the fat oxidation rate for every min throughout the Fatmax stage was evaluated, the average value of the 4th min was significantly lower than that of the 2nd and 3rd min (p < 0.01). In addition, the 5th and 6th min fat oxidation rates were significantly lower than the rates of the 1st, 2nd, 3rd, and 4th min (0.30 ± 0.01 and 0.29 ± 0.01 g/min for the 5th and 6th min, respectively, vs. 0.35 ± 0.02, 0.34 ± 0.02, 0.33 ± 0.02, and 0.31 ± 0.01 g/min for the 1st, 2nd, 3rd, and 4th min, respectively; p < 0.01). Most of the participants had MFO rates in the 1st min of the stage (16/35 participants), and the MFO rates of the remaining participants were observed in the 2nd, 3rd, and 4th min (7/35, 4/35, and 8/35 participants, respectively). None of the participants had MFO rates in the 5th or 6th min. The individual MFO rate (highest fat oxidation rate during Fatmax) was significantly higher than the fat oxidation rate calculated with the last 2 min average values (0.36 ± 0.02 and 0.30 ± 0.01 g/min, respectively; p < 0.05). In conclusion, the calculation of the fat oxidation rate by averaging the last portion of the Fatmax stage data may cause the underestimation of the MFO rate, which probably occurs earlier in the Fatmax stage.

Key words: Exercise intensity, substrate oxidation, indirect calorimetry, oxygen consumption, respiratory quotient

Key Points
  • Taking the average of the last 2 min to calculate the fat oxidation rate could risk underestimating the actual MFO rate.
  • Individual maximal fat oxidation rates might be observed at different times in the Fatmax stage.
  • Selecting an individual’s maximal fat oxidation rate rather than the average over a time period might give better results.








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