Acute Moderate-Intensity Cycling Exercise: Participants will perform 30 minutes of continuous cycling exercise on a cycle ergometer at an intensity corresponding to 65% of their individual maximal oxygen uptake (VO2max). Both aerobic fitness groups will complete the exercise following an overnight fast. Participants in the high aerobic fitness group will also repeat the exercise one hour after consuming an ad libitum meal. Respiratory gas exchange will be measured throughout exercise to calculate fat and carbohydrate oxidation, and rating of perceived exertion will be recorded every five minutes using the Borg 6-20 scale.
Ad Libitum Mixed Meal: One hour after completing the fasted exercise test, participants in the high aerobic fitness group will be provided with an ad libitum mixed meal consisting of pasta and meatballs and will be allowed to eat until comfortably full. One hour after the meal, resting metabolic rate measurement and the 30-minute cycling exercise test at 65% of VO2max will be repeated under the fed condition. No blood samples will be collected during the fed condition.
Study summary
The aim of this study is to investigate the effects of aerobic fitness level, feeding status, and acute exercise on whole-body metabolic fuel utilization and mitochondrial function in peripheral blood mononuclear cells (PBMCs) in healthy young men.
The main questions it aims to answer are:
1. Do individuals with high and low aerobic fitness levels differ in fat and carbohydrate oxidation at rest and during exercise following an overnight fast, and do their PBMC mitochondrial responses to acute exercise differ?
2. Does feeding alter fat and carbohydrate oxidation at rest and during exercise compared with the fasted state in individuals with high aerobic fitness?
3. Are PBMC mitochondrial respiration parameters and their exercise-induced changes associated with fat and carbohydrate oxidation during fasted exercise?
Eligibility
Sex
MALE
Min age
18 Years
Max age
25 Years
Healthy volunteers
Accepted
Inclusion Criteria:
* Healthy male volunteers aged 18-25 years
* Body mass index between 18.5 and 24.9 kg/m²
* Residing on the Hacettepe University Beytepe Campus
* Eligibility for one of the following aerobic fitness groups
* High aerobic fitness group: maximal oxygen uptake (VO2max) greater than 55 mL/kg/min and regular participation in endurance training.
* Low aerobic fitness group: VO2max lower than 45 mL/kg/min and sedentary or not regularly physically active
Exclusion Criteria:
* Current smoking
* Regular or excessive alcohol consumption
* Any musculoskeletal condition that may limit or prevent exercise
* Allergy to any of the foods provided as part of the study meal
* Currently following a weight-loss or other restrictive diet
Primary outcome measure(s)
Change in PBMC Mitochondrial Oxygen Consumption Rate From Pre- to Post-Exercise — Immediately before and immediately after the fasted 30-minute cycling test at 65% of VO2max. Mitochondrial oxygen consumption rate (OCR) will be measured in peripheral blood mononuclear cells (PBMCs) using a Seahorse XFe96 extracellular flux analyzer. PBMCs will be isolated from venous blood samples collected immediately before and immediately after the fasted 30-minute submaximal cycling test. Pre- to post-exercise changes in OCR will be evaluated between the high and low aerobic fitness groups and examined in relation to whole-body fat and carbohydrate oxidation during exercise.
Change in PBMC Proton Efflux Rate From Pre- to Post-Exercise — Immediately before and immediately after the fasted 30-minute cycling test at 65% of VO2max. Proton efflux rate (PER) will be measured in peripheral blood mononuclear cells (PBMCs) using a Seahorse XFe96 extracellular flux analyzer. PBMCs will be isolated from venous blood samples collected immediately before and immediately after the fasted 30-minute submaximal cycling test. Pre- to post-exercise changes in PER will be evaluated between the high and low aerobic fitness groups and examined in relation to whole-body substrate oxidation during exercise.
Fat Oxidation Rate During Submaximal Exercise — During each 30-minute submaximal cycling test performed at 65% of VO2max. Whole-body fat oxidation rate, expressed in grams per minute (g/min), will be calculated using the Frayn stoichiometric equation from oxygen consumption (VO2) and carbon dioxide production (VCO2) measured by indirect calorimetry during 30 minutes of cycling at 65% of the participant's individual VO2max. Fat oxidation will be compared between the high and low aerobic fitness groups under fasted conditions and between the fasted and fed conditions within the high aerobic fitness group.
Carbohydrate Oxidation Rate During Submaximal Exercise — During each 30-minute submaximal cycling test performed at 65% of VO2max. Whole-body carbohydrate oxidation rate, expressed in grams per minute (g/min), will be calculated using the Frayn stoichiometric equation from oxygen consumption (VO2) and carbon dioxide production (VCO2) measured by indirect calorimetry during 30 minutes of cycling at 65% of the participant's individual VO2max. Carbohydrate oxidation will be compared between the high and low aerobic fitness groups under fasted conditions and between the fasted and fed conditions within the high aerobic fitness group.
This page summarises publicly available registry data for informational purposes — not medical advice. Eligibility is determined by each study team; patients should discuss participation with their clinician.
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