Physical FitnessNCT07813403
Effects of Acute Exercise in Fasting and Fed States in Individuals With Different Aerobic Fitness Levels
A study testing Acute Moderate-Intensity Cycling Exercise and Ad Libitum Mixed Meal in people with Physical Fitness and Mitochondrial Function, Bioenergetics, run by Hacettepe University at 1 site in Turkey (Türkiye).
Trial 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. Read more about this study
- Who is it for?
- Ages 18 to 25 years, men onlyHealthy volunteers can take part
- Conditions the study is for
- Physical Fitness, Mitochondrial Function, Bioenergetics, Mitochondria
- What is being tested?
- Acute Moderate-Intensity Cycling Exercise and Ad Libitum Mixed Meal
- Type of treatment
- Lifestyle or therapy programme
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 30 participants
- Where
- 1 siteTurkey (Türkiye)
- Study dates
- 15 Nov 2026to 15 Dec 2027
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 25 years
- Men only
- Healthy volunteers accepted
- Adult
Who may be able to join
- 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
Who cannot join
- 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
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Turkey (Türkiye)1 site
Hacettepe University, Faculty of Sport Sciences
Ankara, Ankara, 06800
Burcu ÖZALP, MSc Student, +905539286638, burcu.ozalp@hacettepe.edu.tr
Süleyman BULUT, PhD, +903122976890 ext. 137, slmbulut@hacettepe.edu.tr
About this study
Official title: The Effect of Acute Exercise in the Fasted and Fed States on Peripheral Blood Mononuclear Cells and Metabolic Fuel Utilization in Individuals With Different Aerobic Fitness Levels
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:
- 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?
- Does feeding alter fat and carbohydrate oxidation at rest and during exercise compared with the fasted state in individuals with high aerobic fitness?
- Are PBMC mitochondrial respiration parameters and their exercise-induced changes associated with fat and carbohydrate oxidation during fasted exercise?
Read the detailed description
This experimental study uses a mixed design incorporating both between- and within-subject comparisons to investigate the influence of aerobic fitness level, feeding status, and acute exercise on substrate oxidation and peripheral blood mononuclear cell (PBMC) mitochondrial function. Between-group comparisons will examine differences between individuals with high and low aerobic fitness under standardized fasted conditions, whereas within-subject comparisons of fasted and fed conditions will be performed in the high-fitness group. In addition, the repeatability of substrate oxidation measurements will be assessed in the high-fitness group.
A total of 30 healthy men aged 18-25 years with a body mass index (BMI) of 18.5-24.9 kg·m-² will be recruited. Participants will be classified into two groups according to maximal oxygen uptake (V̇O₂max). The high-fitness group will comprise 15 endurance-trained individuals with a V̇O₂max >55 mL·kg-¹·min-¹, whereas the low-fitness group will comprise 15 sedentary or physically inactive individuals with a V̇O₂max <45 mL·kg-¹·min-¹.
During the first laboratory visit, participants in both groups will undergo body composition assessment using dual-energy X-ray absorptiometry (DXA) and complete an incremental cycling test to determine V̇O₂max. Following sufficient recovery, participants will complete a 20-min familiarization cycling session at an intensity corresponding to 65% of V̇O₂max.
Participants in the high-fitness group will complete four laboratory visits in total. During the second and third visits, participants will arrive at the laboratory following an overnight fast. Resting metabolic rate (RMR) will be assessed, after which participants will complete 30 min of cycling exercise at 65% of V̇O₂max. These visits will be performed under identical standardized conditions to determine the repeatability of substrate oxidation measurements.
During the fourth visit, participants in the high-fitness group will arrive at the laboratory following an approximately 12-h overnight fast. RMR will first be assessed, followed by the collection of a venous blood sample immediately before exercise. Participants will then complete 30 min of cycling at 65% of V̇O₂max, and a second venous blood sample will be collected immediately after exercise. These samples will be used to assess exercise-induced changes in PBMC mitochondrial function under fasted conditions.
One hour after completing the fasted exercise trial, participants will consume an ad libitum meal consisting of pasta and meatballs. One hour after completion of the meal, RMR assessment and the 30-min cycling exercise trial at 65% of V̇O₂max will be repeated under fed conditions. No blood samples will be collected during the fed condition. Accordingly, comparisons between fasted and fed conditions will be restricted to outcomes related to whole-body substrate metabolism.
Participants in the low-fitness group will complete two laboratory visits. The first visit will include DXA assessment, determination of V̇O₂max, and the familiarization cycling session, as described above. During the second visit, participants will complete the fasted experimental condition. Following an approximately 12-h overnight fast, RMR will be assessed and a venous blood sample will be collected immediately before exercise. Participants will then complete 30 min of cycling at 65% of V̇O₂max, followed immediately by collection of a second venous blood sample. The low-fitness group will not complete the repeatability trials or the fed condition. Therefore, between-group comparisons of substrate oxidation and PBMC mitochondrial function will be performed using data obtained under the standardized fasted condition.
Respiratory gas exchange will be continuously measured during resting and exercise assessments to determine oxygen consumption (V̇O₂) and carbon dioxide production (V̇CO₂). These measurements will be used to calculate rates of fat and carbohydrate oxidation. Rating of perceived exertion (RPE) will be recorded every 5 min during exercise using the Borg 6-20 scale.
PBMCs will be isolated from venous blood samples collected immediately before and after the fasted exercise test. Mitochondrial oxygen consumption rate and proton efflux rate will be measured using a Seahorse XFe96 extracellular flux analyzer. These measurements will be used to evaluate exercise-induced changes in PBMC mitochondrial function and their relationship with whole-body fat and carbohydrate oxidation during exercise.
Participants will also complete a 24-hour dietary intake record before the main experimental visit.
- Being tested
- Acute Moderate-Intensity Cycling Exercise, Ad Libitum Mixed Meal
- Keywords
- Aerobic Fitness, Metabolic Flexibility, Metabolic Fuel Utilization, Substrate Oxidation, Fasted Exercise, Acute Exercise, Peripheral Blood Mononuclear Cells, Mitochondrial Respiration, Indirect Calorimetry, Maximal Oxygen Uptake, Fat Oxidation, Carbohydrate Oxidation
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Acute Moderate-Intensity Cycling ExerciseBehavioural
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 MealOther
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 group | Role | What they receive |
|---|---|---|
| High Aerobic Fitness: Fasted and Fed Conditions | Experimental | Participants with a VO2max greater than 55 mL/kg/min who regularly perform endurance training will be assigned to this arm. Participants will complete two repeatability visits under overnight-fasted conditions, including resting metabolic rate measurement followed by 30 minutes of cycling at 65% of VO2max. During the main experimental visit, they will complete the same measurements in the fasted state, with venous blood samples collected immediately before and after exercise. They will subsequently consume an ad libitum meal, and one hour later, resting metabolic rate measurement and the cycling exercise test will be repeated in the fed state. Receives: Behavioral: Acute Moderate-Intensity Cycling Exercise; Other: Ad Libitum Mixed Meal |
| Low Aerobic Fitness: Fasted Condition | Other | Participants with a VO2max lower than 45 mL/kg/min who are sedentary or physically inactive will be assigned to this arm. Participants will complete the fasted experimental condition only. Following an overnight fast, resting metabolic rate will be measured and a venous blood sample will be collected immediately before 30 minutes of cycling at 65% of VO2max. A second venous blood sample will be collected immediately after exercise. Participants in this arm will not complete the repeatability visits or the fed experimental condition. Receives: Behavioral: Acute Moderate-Intensity Cycling Exercise |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change in PBMC Mitochondrial Oxygen Consumption Rate From Pre- to Post-Exercise
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.
Measured: Immediately before and immediately after the fasted 30-minute cycling test at 65% of VO2max.
Change in PBMC Proton Efflux Rate From Pre- to Post-Exercise
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.
Measured: Immediately before and immediately after the fasted 30-minute cycling test at 65% of VO2max.
Fat Oxidation Rate During Submaximal Exercise
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.
Measured: During each 30-minute submaximal cycling test performed at 65% of VO2max.
Carbohydrate Oxidation Rate During Submaximal Exercise
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.
Measured: During each 30-minute submaximal cycling test performed at 65% of VO2max.
Secondary outcomes (4)
Resting Fat Oxidation Rate
Resting fat oxidation rate, expressed in grams per minute (g/min), will be calculated from oxygen consumption (VO2) and carbon dioxide production (VCO2) measured by indirect calorimetry during the resting metabolic assessment. Resting 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.
Measured: During the resting metabolic assessment before the fasted and fed exercise conditions.
Resting Carbohydrate Oxidation Rate
Resting carbohydrate oxidation rate, expressed in grams per minute (g/min), will be calculated from oxygen consumption (VO2) and carbon dioxide production (VCO2) measured by indirect calorimetry during the resting metabolic assessment. Resting 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.
Measured: During the resting metabolic assessment before the fasted and fed exercise conditions.
PBMC Glycolytic Proton Efflux Rate (glycoPER)
Glycolytic proton efflux rate (glycoPER) will be calculated from the total proton efflux rate after correction for the mitochondrial contribution to extracellular acidification. Measurements will be obtained from PBMCs isolated from venous blood samples collected immediately before and immediately after the fasted submaximal exercise test using a Seahorse XFe96 extracellular flux analyzer.
Measured: Immediately before and immediately after the fasted 30-minute cycling test at 65% of VO2max.
Resting Metabolic Rate
Resting metabolic rate, expressed in kilocalories per day (kcal/day), will be measured using a Q-NRG indirect calorimetry system in canopy mode. Measurements will be performed after an overnight fast in both aerobic fitness groups. In the high aerobic fitness group, resting metabolic rate will also be reassessed one hour after the ad libitum meal and before the fed exercise test.
Measured: Before fasted exercise in both groups and 1 hour after the meal before fed exercise in the high-fitness group.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted10 Sep 2026
- Study start15 Nov 2026 (estimated)
- Primary completion15 Nov 2027 (estimated)
- Study completion15 Dec 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (6)Papers the sponsor has linked to this study.
- Other trials for Physical FitnessStudies of the same condition, open and under way.
- More trials run by Hacettepe UniversityThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Parallel groups
- Model description
- Participants will be non-randomly classified into two parallel groups according to measured maximal oxygen uptake (VO2max) and habitual training status. The high aerobic fitness group will complete repeated fasted assessments and a main experimental visit including fasted and fed exercise conditions in a fixed order. The low aerobic fitness group will complete the fasted experimental condition only. Both groups will perform 30 minutes of cycling exercise at 65% of their individual VO2max.
- Masking
- None (open label)
- Enrolment
- 30 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Hacettepe University
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Suleyman Bulut, Hacettepe University
- Investigators
- Süleyman BULUT, PhD, Principal investigator, Hacettepe University, Faculty of Sport SciencesMuhammed M ATAKAN, PhD, Principal investigator, Hacettepe University, Faculty of Sport Sciences
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07813403
- Sponsor's protocol ID
- SBA 26/387
- Status last verified
- Sep 2026
- First submitted
- 4 Sep 2026
- Last updated
- 10 Sep 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No: Individual participant data will not be shared due to participant confidentiality and the absence of institutional data sharing infrastructure.
Publications
Hedges CP, Woodhead JST, Wang HW, Mitchell CJ, Cameron-Smith D, Hickey AJR, Merry TL. Peripheral blood mononuclear cells do not reflect skeletal muscle mitochondrial function or adaptation to high-intensity interval training in healthy young men. J Appl Physiol (1985). 2019 Feb 1;126(2):454-461. doi: 10.1152/japplphysiol.00777.2018. Epub 2018 Dec 20.
PubMed 30571281Mookerjee SA, Goncalves RLS, Gerencser AA, Nicholls DG, Brand MD. The contributions of respiration and glycolysis to extracellular acid production. Biochim Biophys Acta. 2015 Feb;1847(2):171-181. doi: 10.1016/j.bbabio.2014.10.005. Epub 2014 Oct 27.
PubMed 25449966Atakan MM, Guzel Y, Bulut S, Kosar SN, McConell GK, Turnagol HH. Six high-intensity interval training sessions over 5 days increases maximal oxygen uptake, endurance capacity, and sub-maximal exercise fat oxidation as much as 6 high-intensity interval training sessions over 2 weeks. J Sport Health Sci. 2021 Jul;10(4):478-487. doi: 10.1016/j.jshs.2020.06.008. Epub 2020 Jun 18.
PubMed 32565243Theall B, Stampley J, Cho E, Granger J, Johannsen NM, Irving BA, Spielmann G. Impact of acute exercise on peripheral blood mononuclear cells nutrient sensing and mitochondrial oxidative capacity in healthy young adults. Physiol Rep. 2021 Dec;9(23):e15147. doi: 10.14814/phy2.15147.
PubMed 34889067Liepinsh E, Makarova E, Plakane L, Konrade I, Liepins K, Videja M, Sevostjanovs E, Grinberga S, Makrecka-Kuka M, Dambrova M. Low-intensity exercise stimulates bioenergetics and increases fat oxidation in mitochondria of blood mononuclear cells from sedentary adults. Physiol Rep. 2020 Jun;8(12):e14489. doi: 10.14814/phy2.14489.
PubMed 32562386Janssen JJE, Lagerwaard B, Porbahaie M, Nieuwenhuizen AG, Savelkoul HFJ, van Neerven RJJ, Keijer J, de Boer VCJ. Extracellular flux analyses reveal differences in mitochondrial PBMC metabolism between high-fit and low-fit females. Am J Physiol Endocrinol Metab. 2022 Feb 1;322(2):E141-E153. doi: 10.1152/ajpendo.00365.2021. Epub 2022 Jan 10.
PubMed 35001658
Study at a glance
From the registry record, last updated by the sponsor on 10 Sep 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Effect of Acute Exercise in the Fasted and Fed States on Peripheral Blood Mononuclear Cells and Metabolic Fuel Utilization in Individuals With Different Aerobic Fitness Levels
- ClinicalTrials.gov ID
- NCT07813403
- Acronym / sponsor ID
- SBA 26/387
- Keywords
- Aerobic Fitness, Metabolic Flexibility, Metabolic Fuel Utilization, Substrate Oxidation, Fasted Exercise, Acute Exercise, Peripheral Blood Mononuclear Cells, Mitochondrial Respiration
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 30 participants (estimated)
- Lead sponsor
- Hacettepe UniversityUniversity, hospital or other
- Study start
- 15 Nov 2026 (estimated)
- Primary completion
- 15 Nov 2027 (estimated)
- Study completion
- 15 Dec 2027 (estimated)
- First posted
- 10 Sep 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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:
- 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?
- Does feeding alter fat and carbohydrate oxidation at rest and during exercise compared with the fasted state in individuals with high aerobic fitness?
- Are PBMC mitochondrial respiration parameters and their exercise-induced changes associated with fat and carbohydrate oxidation during fasted exercise?
Detailed description
This experimental study uses a mixed design incorporating both between- and within-subject comparisons to investigate the influence of aerobic fitness level, feeding status, and acute exercise on substrate oxidation and peripheral blood mononuclear cell (PBMC) mitochondrial function. Between-group comparisons will examine differences between individuals with high and low aerobic fitness under standardized fasted conditions, whereas within-subject comparisons of fasted and fed conditions will be performed in the high-fitness group. In addition, the repeatability of substrate oxidation measurements will be assessed in the high-fitness group.
A total of 30 healthy men aged 18-25 years with a body mass index (BMI) of 18.5-24.9 kg·m-² will be recruited. Participants will be classified into two groups according to maximal oxygen uptake (V̇O₂max). The high-fitness group will comprise 15 endurance-trained individuals with a V̇O₂max >55 mL·kg-¹·min-¹, whereas the low-fitness group will comprise 15 sedentary or physically inactive individuals with a V̇O₂max <45 mL·kg-¹·min-¹.
During the first laboratory visit, participants in both groups will undergo body composition assessment using dual-energy X-ray absorptiometry (DXA) and complete an incremental cycling test to determine V̇O₂max. Following sufficient recovery, participants will complete a 20-min familiarization cycling session at an intensity corresponding to 65% of V̇O₂max.
Participants in the high-fitness group will complete four laboratory visits in total. During the second and third visits, participants will arrive at the laboratory following an overnight fast. Resting metabolic rate (RMR) will be assessed, after which participants will complete 30 min of cycling exercise at 65% of V̇O₂max. These visits will be performed under identical standardized conditions to determine the repeatability of substrate oxidation measurements.
During the fourth visit, participants in the high-fitness group will arrive at the laboratory following an approximately 12-h overnight fast. RMR will first be assessed, followed by the collection of a venous blood sample immediately before exercise. Participants will then complete 30 min of cycling at 65% of V̇O₂max, and a second venous blood sample will be collected immediately after exercise. These samples will be used to assess exercise-induced changes in PBMC mitochondrial function under fasted conditions.
One hour after completing the fasted exercise trial, participants will consume an ad libitum meal consisting of pasta and meatballs. One hour after completion of the meal, RMR assessment and the 30-min cycling exercise trial at 65% of V̇O₂max will be repeated under fed conditions. No blood samples will be collected during the fed condition. Accordingly, comparisons between fasted and fed conditions will be restricted to outcomes related to whole-body substrate metabolism.
Participants in the low-fitness group will complete two laboratory visits. The first visit will include DXA assessment, determination of V̇O₂max, and the familiarization cycling session, as described above. During the second visit, participants will complete the fasted experimental condition. Following an approximately 12-h overnight fast, RMR will be assessed and a venous blood sample will be collected immediately before exercise. Participants will then complete 30 min of cycling at 65% of V̇O₂max, followed immediately by collection of a second venous blood sample. The low-fitness group will not complete the repeatability trials or the fed condition. Therefore, between-group comparisons of substrate oxidation and PBMC mitochondrial function will be performed using data obtained under the standardized fasted condition.
Respiratory gas exchange will be continuously measured during resting and exercise assessments to determine oxygen consumption (V̇O₂) and carbon dioxide production (V̇CO₂). These measurements will be used to calculate rates of fat and carbohydrate oxidation. Rating of perceived exertion (RPE) will be recorded every 5 min during exercise using the Borg 6-20 scale.
PBMCs will be isolated from venous blood samples collected immediately before and after the fasted exercise test. Mitochondrial oxygen consumption rate and proton efflux rate will be measured using a Seahorse XFe96 extracellular flux analyzer. These measurements will be used to evaluate exercise-induced changes in PBMC mitochondrial function and their relationship with whole-body fat and carbohydrate oxidation during exercise.
Participants will also complete a 24-hour dietary intake record before the main experimental visit.
Study design
- Primary purpose
- Basic science
- Allocation
- Non-randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 2
- Model description
- Participants will be non-randomly classified into two parallel groups according to measured maximal oxygen uptake (VO2max) and habitual training status. The high aerobic fitness group will complete repeated fasted assessments and a main experimental visit including fasted and fed exercise conditions in a fixed order. The low aerobic fitness group will complete the fasted experimental condition only. Both groups will perform 30 minutes of cycling exercise at 65% of their individual VO2max.
| Arm | Type | Receives |
|---|---|---|
| High Aerobic Fitness: Fasted and Fed Conditions | Experimental | Behavioral: Acute Moderate-Intensity Cycling Exercise, Other: Ad Libitum Mixed MealParticipants with a VO2max greater than 55 mL/kg/min who regularly perform endurance training will be assigned to this arm. Participants will complete two repeatability visits under overnight-fasted conditions, including resting metabolic rate measurement followed by 30 minutes of cycling at 65% of VO2max. During the main experimental visit, they will complete the same measurements in the fasted state, with venous blood samples collected immediately before and after exercise. They will subsequently consume an ad libitum meal, and one hour later, resting metabolic rate measurement and the cycling exercise test will be repeated in the fed state. |
| Low Aerobic Fitness: Fasted Condition | Other | Behavioral: Acute Moderate-Intensity Cycling ExerciseParticipants with a VO2max lower than 45 mL/kg/min who are sedentary or physically inactive will be assigned to this arm. Participants will complete the fasted experimental condition only. Following an overnight fast, resting metabolic rate will be measured and a venous blood sample will be collected immediately before 30 minutes of cycling at 65% of VO2max. A second venous blood sample will be collected immediately after exercise. Participants in this arm will not complete the repeatability visits or the fed experimental condition. |
Who may qualify
- Ages
- 18 to 25 years
- Sex
- Male only
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (6 listed)
- 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
Key exclusion criteria (5 listed)
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Acute Moderate-Intensity Cycling ExerciseParticipants 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. | Behavioural | High Aerobic Fitness: Fasted and Fed Conditions, Low Aerobic Fitness: Fasted Condition |
| Ad Libitum Mixed MealOne 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. | Other | High Aerobic Fitness: Fasted and Fed Conditions |
Primary outcome
Change in PBMC Mitochondrial Oxygen Consumption Rate From Pre- to Post-Exercise
Time frame: 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
Time frame: 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
Time frame: 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
Time frame: 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.
4 secondary outcomes
Resting Fat Oxidation Rate
Time frame: During the resting metabolic assessment before the fasted and fed exercise conditions.
Resting Carbohydrate Oxidation Rate
Time frame: During the resting metabolic assessment before the fasted and fed exercise conditions.
PBMC Glycolytic Proton Efflux Rate (glycoPER)
Time frame: Immediately before and immediately after the fasted 30-minute cycling test at 65% of VO2max.
Resting Metabolic Rate
Time frame: Before fasted exercise in both groups and 1 hour after the meal before fed exercise in the high-fitness group.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 10 Sep 2026.
- Background: PubMed 30571281Hedges CP, Woodhead JST, Wang HW, Mitchell CJ, Cameron-Smith D, Hickey AJR, Merry TL. Peripheral blood mononuclear cells do not reflect skeletal muscle mitochondrial function or adaptation to high-intensity interval training in healthy young men. J Appl Physiol (1985). 2019 Feb 1;126(2):454-461. doi: 10.1152/japplphysiol.00777.2018. Epub 2018 Dec 20.
- Background: PubMed 25449966Mookerjee SA, Goncalves RLS, Gerencser AA, Nicholls DG, Brand MD. The contributions of respiration and glycolysis to extracellular acid production. Biochim Biophys Acta. 2015 Feb;1847(2):171-181. doi: 10.1016/j.bbabio.2014.10.005. Epub 2014 Oct 27.
- Background: PubMed 32565243Atakan MM, Guzel Y, Bulut S, Kosar SN, McConell GK, Turnagol HH. Six high-intensity interval training sessions over 5 days increases maximal oxygen uptake, endurance capacity, and sub-maximal exercise fat oxidation as much as 6 high-intensity interval training sessions over 2 weeks. J Sport Health Sci. 2021 Jul;10(4):478-487. doi: 10.1016/j.jshs.2020.06.008. Epub 2020 Jun 18.
- Background: PubMed 34889067Theall B, Stampley J, Cho E, Granger J, Johannsen NM, Irving BA, Spielmann G. Impact of acute exercise on peripheral blood mononuclear cells nutrient sensing and mitochondrial oxidative capacity in healthy young adults. Physiol Rep. 2021 Dec;9(23):e15147. doi: 10.14814/phy2.15147.
- Background: PubMed 32562386Liepinsh E, Makarova E, Plakane L, Konrade I, Liepins K, Videja M, Sevostjanovs E, Grinberga S, Makrecka-Kuka M, Dambrova M. Low-intensity exercise stimulates bioenergetics and increases fat oxidation in mitochondria of blood mononuclear cells from sedentary adults. Physiol Rep. 2020 Jun;8(12):e14489. doi: 10.14814/phy2.14489.
- Background: PubMed 35001658Janssen JJE, Lagerwaard B, Porbahaie M, Nieuwenhuizen AG, Savelkoul HFJ, van Neerven RJJ, Keijer J, de Boer VCJ. Extracellular flux analyses reveal differences in mitochondrial PBMC metabolism between high-fit and low-fit females. Am J Physiol Endocrinol Metab. 2022 Feb 1;322(2):E141-E153. doi: 10.1152/ajpendo.00365.2021. Epub 2022 Jan 10.
- Individual participant dataSharing planned: No. Individual participant data will not be shared due to participant confidentiality and the absence of institutional data sharing infrastructure.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Süleyman BULUT, PhD principal investigator
Hacettepe University, Faculty of Sport Sciences
Muhammed M ATAKAN, PhD principal investigator
Hacettepe University, Faculty of Sport Sciences
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Acute Moderate-Intensity Cycling Exercise and Ad Libitum Mixed Meal in people with Physical Fitness and Mitochondrial Function, Bioenergetics, run by Hacettepe University at 1 site in Turkey (Türkiye).
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 5 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 10 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Turkey (Türkiye). Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Burcu ÖZALP, MSc student (+905539286638, burcu.ozalp@hacettepe.edu.tr), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change in PBMC Mitochondrial Oxygen Consumption Rate From Pre- to Post-Exercise (time frame: Immediately before and immediately after the fasted 30-minute cycling test at 65% of VO2max.). The study lists 4 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT07813403, which also lists 6 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 10 Sep 2026.