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Completed

NCT Number: NCT07719296

HIIT, Cardiorespiratory Fitness, and Metabolic Health in Healthy Young Adults

The purpose of this study was to investigate the effects of a high-intensity interval training (HIIT) intervention on cardiorespiratory fitness (CRF) and cardiometabolic health in active male university students. The main question it aims to answer is: Does HIIT improves CRF and cardiometabolic outcomes, including blood pressure, lipid profile, and insulin resistance estimated using the homeostasis model assessment of insulin resistance (HOMA-IR). Researchers will compare HIIT (designed to experimental group) to non-training intervention (designed to control group) to see if the training program works to improve the cardiometabolic health status. The HIIT program consisted of three sessions per week for 9 weeks, comprising of three sets of six to eight 30-second running bouts performed at 100-110% of maximal aerobic speed (MAS), interspersed with 30-second active recovery runs at 50% MAS between bouts.

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Key information

Conditions

Metabolic Health Cardio Respiratory Fitness Glucose Metabolism Disorders Hyperinsulinism Insulin Resistance Metabolic Diseases Nutritional and Metabolic Diseases

Age range

19 year–25 year

Sex eligibility

Male

Study type

Interventional

Phase

Not applicable

Primary location

Tunisia

El Kef, Boulifa, 7100, Tunisia

About this study

High-intensity interval training (HIIT) is a time-efficient exercise strategy for improving physical fitness. However, limited evidence is available regarding its effects on cardiometabolic health, including blood pressure, blood lipid profile, glucose metabolism, and insulin resistance, in healthy young adults. The purpose of this randomized controlled trial was to investigate the effects of a 9-week HIIT intervention on cardiorespiratory fitness (CRF), blood pressure, blood lipid profile, glucose, insulin, and insulin resistance estimated using the homeostasis model assessment of insulin resistance (HOMA-IR) in physically active male university students. Twenty-nine healthy male students at the High Institute of Sport and Physical Education of Kef (Tunisia) were randomly assigned to either the HIIT group (HIITG, n=15) or the control group (CG, n=14). The HIIT group completed a supervised training program consisting of three sessions per week for 9 weeks, comprising of three sets of six to eight 30-second running bouts performed at 100-110% of maximal aerobic speed (MAS), interspersed with 30-second active recovery runs at 50% MAS between bouts. Outcome assessments were performed before and after the intervention. Cardiorespiratory fitness was evaluated by maximal oxygen consumption (VO₂max) and maximal aerobic speed (MAS) using the Vameval incremental running test. Cardiometabolic outcomes included systolic and diastolic blood pressure, total cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), fasting glucose, fasting insulin, and insulin resistance estimated using the homeostasis model assessment of insulin resistance (HOMA-IR).

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Male university students at the High Institute of Sport and Physical Education, Kef, Tunisia.
  • Aged 19 to 25 years
  • Provided written informed consent

Exclusion criteria

  • Acute or chronic disease contraindicating vigorous physical exercise
  • Musculoskeletal injury or any other medical condition limiting participation in exercise
  • Participation in another structured training program within the previous 6 months
  • Current or recent (within the previous 3 months) use of medications or dietary supplements that could influence the study outcomes

Treatment and study plan

High-intensity interval training (HIIT) program

Behavioral

The HIIT program consisted of three sessions per week for 9 weeks, comprising of three sets of sixr to eight bouts of 30-second runs at high intensity [100-110% of maximal aerobic speed (MAS)], interspersed with 30-second recovery runs at low intensity (50% MAS) between bouts.

Primary outcomes

  1. Insulin resistance

    Time frame: One day before the start and two days after the completion of the 09 weeks of training program.

    Insulin resistance was estimated by the homeostasis model assessment (HOMA-IR) index as HOMA-IR = (fasting insulin (mU/l) × fasting glucose (mmol/l) / 22.5)) (Matthews et al., 1985).

  2. Total cholesterol

    Time frame: One day before the start and two days after the completion of the 09 weeks of training program.

    Total cholesterol concentration, expressed in mg/dL, was assessed by the enzymatic method on an Architect C8000 auto analyzer (Abbott Laboratories, Abbott Park, IL) using respective reagent kits.

  3. Triglyceride

    Time frame: One day before the start and two days after the completion of the 09 weeks of training program.

    Triglyceride concentration, expressed in mg/dL, was assessed by the enzymatic method on an Architect C8000 auto analyzer (Abbott Laboratories, Abbott Park, IL) using respective reagent kits.

  4. Blood pressure

    Time frame: One day before the start and two days after the completion of the 09 weeks of training program

    Blood pressure, expressed in mmHg, was measured after 15 minutes of seated rest using an automatic blood pressure monitor (Omron BP652; Omron Healthcare Inc., Vernon Hills, IL, USA).

  5. Cardiorespiratory fitness

    Time frame: One day before the start and two days after the completion of the 09 weeks of training program.

    Cardiorespiratory fitness was assessed using the Vameval incremental running test performed to exhaustion (Cazorla, 1999). Maximal aerobic speed (MAS) was determined from the highest running speed achieved during the test, and maximal oxygen consumption (VO2max) was estimated using the standard Vameval protocol (Cazorla, 1999). The Vameval test is a validated field test for assessing aerobic capacity in healthy young adults.

  6. Body mass index

    Time frame: One day before the start and two days after the completion of the 09 weeks of training program

    Body mass index (BMI), expressed in kg/m², was calculated from measured body mass (kg) and height (m) using the standard formula: BMI = body mass (kg) / height² (m²). Body mass and height were used only to derive BMI and were not considered separate outcome measures.

  7. Body fat percentage

    Time frame: One day before the start and two days after the completion of the 09 weeks of training program.

    Body fat percentage (%) was estimated from four skinfold measurements (bicipital, triceps, subscapular, and suprailiac) using the Durnin and Womersley (1973) method.

Secondary outcomes

  1. Fasting glucose

    Time frame: One day before the start and two days after the completion of the 09 weeks of training program.

    Fasting glucose concentration, expressed in mg/dL, was assessed by the enzymatic method on an Architect C8000 auto analyzer (Abbott Laboratories, Abbott Park, IL) using respective reagent kits.

  2. Insulin

    Time frame: One day before the start and two days after the completion of the 09 weeks of training program.

    Insulin concentration, expressed in µU/mL, was measured by chemiluminescence immunoassay using a Liaison analyzer and the respective reagents kit (DiaSorin Inc., Stillwater, MN, USA).

  3. High-density lipoprotein cholesterol

    Time frame: One day before the start and two days after the completion of the 09 weeks of training program.

    High-density lipoprotein cholesterol, expressed in mg/dL, was assessed by the enzymatic method on an Architect C8000 auto analyzer (Abbott Laboratories, Abbott Park, IL) using respective reagent kits.

  4. Low-density lipoprotein cholesterol

    Time frame: One day before the start and two days after the completion of the 09 weeks of training program

    Low-density lipoprotein cholesterol, expressed in mg/dL, was calculated using the Friedewald formula (Friedewald et al., 1972).

Sponsors and collaborators

Lead sponsor

High Institute of Sports and Physical Education of Kef

Other

Registry information

Official study title

High-intensity Interval Training Improves Cardiorespiratory Fitness and Modestly Enhances Metabolic Health in Healthy Young Adults : a Randomized Controlled Trial

Important dates

Study start
2025
Primary completion
2026
Study completion
2026
First posted
Jul 22, 2026
Registry last updated
Jul 23, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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