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VO2max and Substrate Crossover Point (VO2MAX-CROSS)

28 augusti 2026 uppdaterad av: Celil Kaçoğlu

Higher VO2max Delays Substrate Switching and Shifts the Crossover Point to Greater Oxygen Uptake During Incremental Exerciseebys

This study aims to investigate the relationship between maximal oxygen uptake (VO2max) and the substrate crossover point during incremental exercise. A total of 20 physical education students are recruited to complete a maximal incremental treadmill test using the standard Bruce protocol. Indirect calorimetry is utilized to assess oxygen uptake (VO2), carbon dioxide production (VCO2), and energy substrate utilization patterns. The substrate crossover point is operationally defined at a respiratory exchange ratio (RER) threshold of 0.85, indicating the metabolic transition toward predominant carbohydrate oxidation. The primary objective is to evaluate how variations in aerobic capacity influence the timing, oxygen uptake, and heart rate (HR) responses at this metabolic transition threshold.

Studieöversikt

Status

Avslutad

Betingelser

Intervention / Behandling

Detaljerad beskrivning

This study evaluates the relationship between maximal oxygen uptake (VO2max) and the substrate crossover point during incremental treadmill exercise in young, physically active individuals. Substrate utilization kinetics and metabolic flexibility represent critical components of cardiovascular conditioning and endurance performance; however, the impact of continuous variations in aerobic capacity on the onset of metabolic transition requires detailed investigation.

Participants undergo anthropometric testing followed by a maximal graded exercise test on a motor-driven treadmill following the standard Bruce protocol. Breath-by-breath expired gas analysis using indirect calorimetry continuously monitors oxygen uptake (VO2), carbon dioxide production (VCO2), and minute ventilation (VE) throughout the test. Respiratory exchange ratio (RER) values are calculated continuously. The substrate crossover point is operationally defined as the exercise intensity corresponding to an RER threshold of 0.85, representing the metabolic transition where carbohydrate oxidation becomes the predominant contributor to total energy expenditure over lipid oxidation.

Key outcome measures extracted at this threshold include:

Time to reach the crossover point (minutes)

Absolute oxygen uptake at crossover (liters per minute [L/min])

Relative oxygen uptake at crossover (milliliters per kilogram per minute [mL/kg/min])

Percentage of maximal oxygen uptake at crossover (%VO2max)

Heart rate at crossover (beats per minute [bpm])

Statistical associations between maximal aerobic capacity (VO2max) and the primary outcome measures at the crossover point are analyzed using linear correlation and regression models to determine how cardiorespiratory fitness alters substrate switching kinetics under progressive physical strain.

Studietyp

Interventionell

Inskrivning (Faktisk)

20

Fas

  • Inte tillämpbar

Kontakter och platser

Det här avsnittet innehåller kontaktuppgifter för dem som genomför studien och information om var denna studie genomförs.

Studieorter

  • Turkiet (Türkiye)
    • Tepebaşi
      • Eskişehir, Tepebaşi, Turkiet (Türkiye), 26100
        • Eskişehir Technical University

Deltagandekriterier

Forskare letar efter personer som passar en viss beskrivning, så kallade behörighetskriterier. Några exempel på dessa kriterier är en persons allmänna hälsotillstånd eller tidigare behandlingar.

Urvalskriterier

Åldrar som är berättigade till studier

  • Vuxen

Tar emot friska volontärer

Ja

Beskrivning

Inclusion Criteria:

  • Healthy male or female physical education students aged 18 to 30 years
  • Regularly physically active (participating in structured physical activity at least 3 days per week)
  • Medically cleared and capable of performing maximal graded treadmill exercise testing to voluntary exhaustion
  • Willing and able to provide written informed consent

Exclusion Criteria:

  • History of cardiovascular, pulmonary, metabolic, renal, or neuromuscular disorders
  • Acute musculoskeletal injury or orthopedic condition that impairs treadmill running or maximal exertion
  • Current use of prescription medications, stimulants, or dietary supplements known to alter metabolic rate, heart rate, or substrate oxidation
  • Use of tobacco, nicotine products, or alcohol within 24 hours prior to testing
  • Consumption of caffeine or vigorous physical exercise within 24 hours prior to the exercise trial

Studieplan

Det här avsnittet ger detaljer om studieplanen, inklusive hur studien är utformad och vad studien mäter.

Hur är studien utformad?

Designdetaljer

  • Primärt syfte: Grundläggande vetenskap
  • Tilldelning: N/A
  • Interventionsmodell: Enskild gruppuppgift
  • Maskning: Ingen (Open Label)

Vapen och interventioner

Deltagargrupp / Arm
Intervention / Behandling
Experimentell: Exercise Testing Group
: Healthy young adult participants who undergo a single maximal incremental treadmill exercise test using the Bruce Protocol to assess cardiorespiratory fitness (VO2max) and substrate crossover kinetics.
Beteende: Incremental Graded Exercise Test (Bruce Protocol)
Participants perform a maximal treadmill exercise test following the standardized Bruce Protocol. The test begins with a warm-up, followed by progressive 3-minute stages with continuous increases in speed and incline until voluntary exhaustion. Indirect calorimetry is used continuously via breath-by-breath gas analysis to measure VO2VCO2, and RER for substrate crossover determination.
Andra namn:
  • Bruce Treadmill Protocol
  • Maximal Incremental Exercise Test
  • Graded Exercise Testing (GXT)
  • Maximal Treadmill Exercise Test

Vad mäter studien?

Primära resultatmått

Resultatmått
Åtgärdsbeskrivning
Tidsram
Time to reach the substrate crossover point
Tidsram: Time Frame: Baseline (single test session, Day 1)

Measure Description: Elapsed time (in minutes) from the start of the incremental treadmill test (Bruce protocol) to the point where the respiratory exchange ratio (RER) reaches 0.85, indicating the metabolic crossover where carbohydrate oxidation becomes the predominant fuel source.

Time Frame: Baseline (single exercise test session, Day 1) Unit of Measure: Minutes
Time Frame: Baseline (single test session, Day 1)
Relative oxygen uptake at the crossover point
Tidsram: Measure Description: Measured continuously during the incremental exercise test using indirect calorimetry, recorded specifically at the point where the respiratory exchange ratio (RER) reaches 0.85. Time Frame: Baseline

Measure Title: Relative oxygen uptake at the substrate crossover point Measure Description: Oxygen uptake (VO2) normalized to body weight (mL/kg/min) recorded at the moment the substrate crossover point (respiratory exchange ratio [RER] = 0.85) is reached during the maximal incremental treadmill test (Bruce protocol).

Time Frame: Baseline
Measure Description: Measured continuously during the incremental exercise test using indirect calorimetry, recorded specifically at the point where the respiratory exchange ratio (RER) reaches 0.85. Time Frame: Baseline

Sekundära resultatmått

Resultatmått
Åtgärdsbeskrivning
Tidsram
Percentage of VO2max at the crossover point
Tidsram: Measure Description: Relative oxygen uptake (VO2) at the substrate crossover point (respiratory exchange ratio [RER] = 0.85) expressed as a % of the participant's maximal oxygen uptake (VO2max), calculated upon completion of the Bruce protocol

Measure Title: Percentage of maximal oxygen uptake at the substrate crossover point

Measure Description: Relative oxygen uptake (VO2) at the substrate crossover point (respiratory exchange ratio [RER] = 0.85) expressed as a percentage (%) of the participant's maximal oxygen uptake (VO2max) during the Bruce protocol treadmill test.

Time Frame: Baseline
Measure Description: Relative oxygen uptake (VO2) at the substrate crossover point (respiratory exchange ratio [RER] = 0.85) expressed as a % of the participant's maximal oxygen uptake (VO2max), calculated upon completion of the Bruce protocol
Heart rate at the crossover point
Tidsram: Measure Description: Heart rate (HR) in beats per minute (bpm) measured continuously during the incremental treadmill test (Bruce protocol), recorded at the substrate crossover threshold (respiratory exchange ratio [RER] = 0.85). Time Frame: Baseline

Measure Title: Heart rate at the substrate crossover point Measure Description: Heart rate (HR) recorded in beats per minute (bpm) using a telemetric heart rate monitor at the point where the substrate crossover threshold (respiratory exchange ratio [RER] = 0.85) is achieved during the maximal incremental treadmill test (Bruce protocol).

Time Frame: Baseline
Measure Description: Heart rate (HR) in beats per minute (bpm) measured continuously during the incremental treadmill test (Bruce protocol), recorded at the substrate crossover threshold (respiratory exchange ratio [RER] = 0.85). Time Frame: Baseline
Maximal oxygen consumption (VO2max)
Tidsram: Measure Description: Relative maximal oxygen uptake (VO2max in mL/kg/min) assessed at maximal exertion at the end of the Bruce protocol treadmill test to voluntary exhaustion via indirect calorimetry. Time Frame: Baseline

Measure Description:

The highest rate of relative oxygen uptake (VO2 in mL/kg/min) attained during the maximal graded exercise test (Bruce protocol) to voluntary exhaustion via indirect calorimetry.

Time Frame: Baseline
Measure Description: Relative maximal oxygen uptake (VO2max in mL/kg/min) assessed at maximal exertion at the end of the Bruce protocol treadmill test to voluntary exhaustion via indirect calorimetry. Time Frame: Baseline

Samarbetspartners och utredare

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Sponsor

Celil Kaçoğlu

Utredare

  • Huvudutredare: celil kaçoğlu, Ph.D., Eskişehir Teknik Üniversitesi

Publikationer och användbara länkar

Den som ansvarar för att lägga in information om studien tillhandahåller frivilligt dessa publikationer. Dessa kan handla om allt som har med studien att göra.

Allmänna publikationer

Studieavstämningsdatum

Dessa datum spårar framstegen för inlämningar av studieposter och sammanfattande resultat till ClinicalTrials.gov. Studieposter och rapporterade resultat granskas av National Library of Medicine (NLM) för att säkerställa att de uppfyller specifika kvalitetskontrollstandarder innan de publiceras på den offentliga webbplatsen.

Studera stora datum

Studiestart (Faktisk)

1 maj 2026

Primärt slutförande (Faktisk)

30 juni 2026

Avslutad studie (Faktisk)

15 juli 2026

Studieregistreringsdatum

Först inskickad

25 augusti 2026

Först inskickad som uppfyllde QC-kriterierna

28 augusti 2026

Första postat (Faktisk)

2 september 2026

Uppdateringar av studier

Senaste uppdatering publicerad (Faktisk)

2 september 2026

Senaste inskickade uppdateringen som uppfyllde QC-kriterierna

28 augusti 2026

Senast verifierad

1 augusti 2026

Mer information

Termer relaterade till denna studie

Nyckelord

Andra studie-ID-nummer

  • EskisehirTU-SBF-CK-04

Plan för individuella deltagardata (IPD)

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NEJ

IPD-planbeskrivning

Individual participant data will not be publicly shared due to privacy and ethical constraints aimed at protecting participant confidentiality. However, de-identified aggregated data or specific data sets may be made available from the corresponding author upon reasonable academic request.

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