New Methodological Approach to Metabolic Thresholds Detection; Examining Fat Utilization Points and Metabolic Thresholds Correlation Strength

This study aims to examine the existence of connection between metabolic thresholds and fat oxidation points in diverse group of subjects. From the physiological perspective, during exercise with increasing intensity, three phases of the body's energy utilization and two threshold points can be defined. These threshold points have been named metabolic thresholds and as such are considered as indicators of exercise capacities. Several authors have suggested, that the first threshold should be called the 'aerobic threshold' (AeT) and the second the 'anaerobic threshold' (AnT). The energy contribution from fat oxidation increases during low-to-moderate exercise intensities and then markedly declines when the intensity becomes high, at which point carbohydrates (CHO) remain the dominant energy substrate. A term used to describe exercise intensity where fat oxidation reaches optimum, is maximal fat oxidation point (FATmax) whereas exercise intensity matching the negligible fat oxidation is labelled FATmin. During physical activity, due to limited availability of CHO, subjects are more dependent on energy originating from fat when aiming to optimize endurance performance, body composition, optimize weight control and the metabolic rate. Exercise at the intensity eliciting FATmax revealed best results in treatment and prevention of obesity-associated conditions, cardio-vascular and pulmonary diseases by means of increase in maximal fat oxidation rates (MFO), insulin sensitivity, improvements in ventilator efficiency and cardiac output, demonstrating a significant role in the treatment of these impairments. As a follow-up, studies demonstrated how the lowest beneficial effect was observed when exercise was performed above intensity matching negligible fat oxidation rate (FATmin), contributing to diminished protection of exercise therapy. In consequence, increased cardio-metabolic demands of exercise performed above FATmin also have a higher impact on mortality rates in comparison to low-moderate aerobic exercise. Therefore, choosing appropriate exercise intensity may play a decisive role in decreasing risk factors accompanying obesity-associated conditions.

Investigators aim to determine metabolic thresholds and fat oxidation points by using non-invasive breath-by-breath gas analysis during either treadmill or cycle ergometry. Metabolic thresholds will be detected by using gas analysis, via ventilatory parameters. Fat oxidation points will be determined using indirect calorimetry.

Participants will perform graded ergometry test (2min stages and 1km/h or 50 W load increase), on either cycle or treadmill ergometer, till exhaustion to determine maximal oxygen uptake (VO2max), with gases being collected at the mouth level by using spiroergometry.

The strength of the relationship between intensities matching VO2 at AeT and VO2 at FATmax will be assessed using the Pearson product moment (r) correlation coefficient with same being done for AnT and FATmin correlation. A coefficient of determination (R2) will be used to detect the proportion of existing variance. A paired t-test will be used to asses' differences between measured variables.

Associated heart rate at the AeT/FATmax and AnT/FATmin will be used as training mean to identify proper training intensity.