Evaluating the influence of differences in methodological approach on metabolic thresholds and fat oxidation points relationship

Abstract

In this study, we aimed to determine the exercise intensities eliciting the highest (FAT max ) and the lowest (FAT min ) fat oxidation rate in male cyclists and to compare these intensities with their individual aerobic (AeT) and anaerobic (AnT) thresholds, respectively. Twenty-two moderately trained male cyclists performed a 2-min stage graded exercise test until exhaustion using breath-by-breath gas analysis to determine maximal oxygen consumption (VO 2max ). The fat oxidation rate was calculated using a stoichiometric equation, with metabolic thresholds being determined by ventilatory gas analysis. In the present group of subjects, FAT max was found at a 21.34 ± 3.64 ml•kg −1 •min −1 corresponding to 45.05 ± 7.68% VO 2max . AeT occurred at an exercise intensity of 22.15 ± 4.84 ml•kg −1 •min −1 , matching 46.76 ± 10.24% VO 2max . AnT and FAT min were located at intensities equivalent to 32.56 ± 5.52 ml•kg −1 •min −1 and 32.30 ± 5.35 ml•kg −1 •min −1 which corresponded to 68. 74 ± 11.65 and 68.19 ± 11.29% VO 2max , respectively. The correlation between FAT max and AeT was strong (r = 0.80, p < 0.05). No statistical difference was observed between FAT min and AnT (r = 0.99, p < 0.05). The strong relationship between observed indices can be used to provide a more tailored exercise approach.

Comparison of the Ramp and Step Incremental Exercise Test Protocols in Assessing the Maximal Fat Oxidation Rate in Youth Cyclists

“…The intensity of FAT max expressed as a percentage of VO 2max amounted to ~45% in the RAMP and ~44% in the STEP test. Those results are comparable to those presented by Peric et al (2018) and Nikolovski et al (2020) , but lower than the intensity described in similar research projects involving cyclists ( Achten et al, 2004 ; Bircher et al, 2005 ). The differences may be accounted for the training status, circulatory and respiratory efficiency, and methodological means of FAT max assessment.…”

“…Although MFO was slightly lower in the RAMP test, no statistical significance was demonstrated. That corroborates our first hypothesis which assumed that MFO would not differ between the tests and highlights the possibility of measuring this variable through a RAMP test with a linear power output increase, although previous research had assumed that, in order to delineate MFO it was necessary to reach a steady state (in STEP tests) for the respiratory exchange ratio to reflect cellular metabolic gas exchange ( Nikolovski et al, 2020 ). Attention should be drawn to the wide range of fat oxidation (0.2-1.0 g·min –1 ) observed in youth athletes of similar age, regardless of the type of exercise (test) they perform.…”

“…The differences may be accounted for the training status, circulatory and respiratory efficiency, and methodological means of FAT max assessment. In our research the FAT min intensity occurred in both tests at ~79%, which does not concord with the findings of Nikolovski et al (2020) who established it at 68.2 ± 11.3% VO 2max in moderately trained male cyclists (VO 2max = 47.4 ± 6.4 ml·kg –1 ·min –1 ). Higher values were established in highly trained athletes in the research of Peric et al (2016) , with FAT min amounting to 87.6 ± 1.3% VO 2max .…”

“…Different approaches to defining the maximal fat oxidation level have been suggested based on indirect calorimetry calculations. One of them consists of a single progressive test (IET) with 2 to 6-min stages ( Achten et al, 2002 ; Marzouki et al, 2014 ; Nikolovski et al, 2020 ). Achten et al (2002) suggest that 3-min stages are optimal to reach a state of equilibrum and define MFO for well-trained athletes.…”

Influence of exercise training on diabetic kidney disease: A brief physiological approach

“…There are several possible ways to assess exercise intensity in order to better prescribe an exercise protocol. 80 With regard to aerobic exercise, the most used methods to estimate the relative intensity of exercise is the heart rate reserve (%HRR) or oxygen uptake reserve (%VO 2 R), maximum heart rate (%HR max ), maximum oxygen uptake (%VO 2max ), and rating of perceived exertion (RPE). Regarding the resistance exercise, the main parameter used to determine the intensity is one-repetition maximum (%1-RM).…”