Measurement of Substrate Oxidation During Exercise by Means of Gas Exchange Measurements

Abstract

Measures of substrate oxidation have traditionally been calculated from indirect calorimetry measurements using stoichiometric equations. Although this has proven to be a solid technique and it has become one of the standard techniques to measure whole body substrate metabolism, there are also several limitations that have to be considered. When indirect calorimetry is used during exercise most of the assumptions on which the method is based hold true although changes in the size of the bicarbonate pool at higher exercise intensities may invalidate the calculations of carbohydrate and fat oxidation. Most of the existing equations are based on stoichiometric equations of glucose oxidation and the oxidation of a triacylglycerol that is representative of human adipose tissue. However, in many exercise conditions, glycogen and not glucose is the predominant carbohydrate substrate. Therefore we propose slightly modified equations for the calculation of carbohydrate and fat oxidation for use during low to high intensity exercise. Studies that investigated fat oxidation over a wide range of intensities and that determined the exercise intensity at which fat oxidation is maximal have provided useful insights in the variation in fat oxidation between individuals and in the factors that affect fat oxidation. Fat oxidation during exercise can be influenced by exercise intensity and duration, diet, exercise training, exercise mode and gender. Although a number of important factors regulating fat oxidation have been identified, it is apparent that a considerable degree of inter-subject variability in substrate utilization persists and cannot be explained by the aforementioned factors. Future research should investigate the causes of the large inter-individual differences in fat metabolism between individuals and their links with various disease states.

Relationship between Category of Weight and Threshold of Maximum Oxidation of Lipids in Congolese Judoists

“…However, this undervaluation seems to be proven at the sedentary subjects [17], but "non-existent" statistically among involved fighters [13]. Indeed, Achtenandal., 2002, showed that one duration of three minute old stages would not significantly involve a difference on [21]. Consequently, this difference can be explained by the effect related to the sex (men versus women).…”

Effects of Circuit Resistance Training and P Timely Protein Supplementation on Exercise-Induced Fat Oxidation in Tetraplegic Adults

“…CHO and fat oxidation, caloric equivalent (CQ), and total energy expenditure (TEE) were calculated as previously described using stochiometric equations and assuming that urinary nitrogen excretion was negligible 28 :…”

Limited Benefit of Fatmax-Test to Derive Training Prescriptions

“…Therefore, it appears unlikely that carry-over eff ects impacted the results of the present study. During constant load exercise, the calculation of substrate utilization by means of indirect calorimetry is correct as long as there are lactate steady-state conditions [ 12 ] . If the lactate steady-state is defi ned as no more than 1 mmol/l increase in bLa between the 10 th and 30 th minute of exercise [ 5 ] , 3 subjects were not in a lactate steady-state in the constant load test at Fat max and fi ve were not in a lactate steady state in the HIGH test.…”

“…However, Romijn et al [ 20 ] stated that indirect calorimetry can be used to accurately determine fat and carbohydrate oxidation rates up to exercise intensities of 80-85 % VO 2max . Similarly, Jeukendrup and Wallis [ 12 ] named 75 % VO 2max as the upper limit for calculations of the fat oxidation rate. The intensity of the HIGH test in the present study averaged 70 % VO 2max , which is below this threshold and indicates that the calculated fat oxidation rates were presumably correct.…”