Effects of HIIT and MICT Training on Cardiorespiratory Fitness, Testosterone/Cortisol Ratio, and Mental Health in Young Adults

Effects of HIIT and MICT Training on Cardiorespiratory Fitness, Testosterone/Cortisol Ratio, and Mental Health in Young Adults: an 8-week Randomized Clinical Trial

This study will use a randomized, double-blind clinical trial to evaluate the effects of eight-week HIIT and MICT exercise programs on cardiorespiratory fitness, the testosterone/cortisol ratio, and mental health in 68 healthy, moderately active young adults aged 18 to 21. Participants will be assigned to parallel groups based on their sex and training type (HIIT men, HIIT women, MICT men, MICT women). The key metrics will be measured both before and after the intervention period to assess the impact of the different training regimens.

This randomized, double-blind clinical trial will investigate the effects of high-intensity interval training (HIIT) versus moderate-intensity continuous training (MICT) on cardiorespiratory fitness and symptoms of anxiety and depression in high school students.

The study will recruit 68 male and female students, aged 15-19, who are moderately inactive. Participants will be randomized into HIIT or MICT groups, stratified by gender. The 8-week intervention consists of three weekly sessions: HIIT involves 10x1-minute high-intensity intervals, while MICT consists of 30 minutes of continuous running. Cardiorespiratory fitness (measured via the Course Navette test to estimate VO₂max) and mental health symptoms (using Beck inventories) will be assessed before and after the intervention.

The primary hypothesis is that HIIT will yield greater improvements in VO₂max and greater reductions in anxiety and depression symptoms compared to MICT. Statistical analysis will employ ANOVA and related tests to evaluate changes within and between groups, with a significance level set at p<0.05. The study aims to provide evidence for designing personalized exercise programs that optimize both physical and mental health in adolescents.

Inclusion criteria:

• Men and women aged 18 to 21.
• Lead a sedentary or moderately active lifestyle (IPAQ ≤600 METs-min/week).
• Subjects diagnosed by a physician as fit for physical exercise.
• Informed consent form signed by the study subjects.

Exclusion criteria:

• Subjects with any motor disability.
• Pregnant women.
• Subjects with metabolic disorders.
• Subjects with chronic respiratory diseases such as asthma, emphysema, or cancer, obstructive pulmonary disease.
• Subjects with high blood pressure or arrhythmia.
• Failure to sign the informed consent form.
• Subjects who are in a high-performance physical training program.
• Women with irregular menstrual cycles who take contraceptive medication to regulate their menstrual cycle.
• Consumption of caffeine, alcohol, and tobacco or use of electronic cigarettes.
• Subjects with a cyclical diagnosis of anxiety and depression by a specialist.
• Frequent consumption of alcoholic beverages (more than 7 drinks per week for women and more than 14 drinks per week for men) or a history of excessive alcohol consumption.
• Subjects who consume dietary supplements (caffeine, nitric oxide precursors, beta-alanine, creatine, sodium bicarbonate, or L-carnitine).

Elimination criteria:

• Voluntary withdrawal from the study.
• Attendance at less than 80% of intervention sessions.
• Incomplete measurement schedule or insufficient sample size.
• Joint or muscle injuries caused by the training program.
• Overtraining syndrome.