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

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

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.

Study Overview

• Status: Completed
• Conditions: Metabolic Health; Cardio Respiratory Fitness
• Intervention / Treatment: Behavioral: High-intensity interval training (HIIT) program

Detailed Description

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).

• Study Type: Interventional
• Enrollment (Actual): 29
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Tunisia
  • Boulifa
    • El Kef, Boulifa, Tunisia, 7100
      • Tunisia

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
No Intervention: Control group; The participants in the control group maintained their normal daily activities.
Experimental: High-intensity interval training (HIIT) group; The HIIT group performed a HIIT program consisting of three sessions per week for 9 weeks, including three sets of six 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, in line with recommendations by Ouerghi et al. (2017, 2026) in young males.	Behavioral: High-intensity interval training (HIIT) program; 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Insulin resistance	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).	One day before the start and two days after the completion of the 09 weeks of training program.
Total cholesterol	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.	One day before the start and two days after the completion of the 09 weeks of training program.
Triglyceride	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.	One day before the start and two days after the completion of the 09 weeks of training program.
Blood pressure	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).	One day before the start and two days after the completion of the 09 weeks of training program
Body mass index	Body mass index (BMI), expressed in kg/m², was calculated using the following formula: BMI = body mass (kg) / height² (m²).	One day before the start and two days after the completion of the 09 weeks of training program
Cardiorespiratory fitness	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.	One day before the start and two days after the completion of the 09 weeks of training program.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Fasting glucose	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.	One day before the start and two days after the completion of the 09 weeks of training program.
Insulin	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).	One day before the start and two days after the completion of the 09 weeks of training program.
High-density lipoprotein cholesterol	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.	One day before the start and two days after the completion of the 09 weeks of training program.
Low-density lipoprotein cholesterol	Low-density lipoprotein cholesterol, expressed in mg/dL, was calculated using the Friedewald formula (Friedewald et al., 1972).	One day before the start and two days after the completion of the 09 weeks of training program

Collaborators and Investigators

• Sponsor: High Institute of Sports and Physical Education of Kef
• Investigators: Principal Investigator: Nejmeddine Ouerghi, Ph.D, Research Unit "Sport Sciences, Health and Movement"(UR22JS01) High Institute of Sport and Physical Education of Kef, University of Jendouba, 7100 Kef, Tunisia.

Study record dates

Study Major Dates

• Study Start (Actual): December 1, 2025
• Primary Completion (Actual): February 16, 2026
• Study Completion (Actual): February 16, 2026

Study Registration Dates

• First Submitted: July 17, 2026
• First Submitted That Met QC Criteria: July 17, 2026
• First Posted (Actual): July 22, 2026

Study Record Updates

• Last Update Posted (Actual): July 22, 2026
• Last Update Submitted That Met QC Criteria: July 17, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: Insulin resistance; Lipid profile; Young adults; Aerobic fitness; Cardiometabolic health; Training period
• Additional Relevant MeSH Terms: Metabolic Diseases; Glucose Metabolism Disorders; Hyperinsulinism; Nutritional and Metabolic Diseases; Insulin Resistance; Motor Activity; Movement; Musculoskeletal Physiological Phenomena; Musculoskeletal and Neural Physiological Phenomena; Physical Conditioning, Human; Exercise; High-Intensity Interval Training
• Other Study ID Numbers: HIIT-MET-STUDENTS

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No