Autonomic Response to the Harvard Step Test in Normal BMI and Overweight Young Adults: A Heart Rate Variability Study

Area of Science:

• Cardiology
• Autonomic Nervous System Function
• Exercise Physiology

Background:

• Excess adiposity in young adults is linked to early autonomic imbalance, potentially preceding cardiovascular disease.
• Heart rate variability (HRV) is a non-invasive indicator of cardiac autonomic modulation.
• Understanding HRV differences between normal weight and overweight young adults is crucial for early detection of health risks.

Purpose of the Study:

• To compare resting and early post-exercise HRV between normal body mass index (BMI) and overweight young adults.
• To identify specific HRV parameters indicative of autonomic dysfunction in overweight individuals.
• To assess the impact of the Harvard Step Test on HRV in different BMI groups.

Main Methods:

• A comparative study involving 200 young adults (17-25 years), divided into normal BMI (n=100) and overweight (n=100) groups.
• Baseline and post-exercise (Harvard Step Test) electrocardiography (ECG) recordings were used to analyze time-domain (SDNN, RMSSD, NN50, pNN50) and frequency-domain (HF power, LF/HF ratio) HRV parameters.
• Statistical analyses included regression and mixed-effects modeling to identify independent associations and group-time interactions.

Main Results:

• Overweight individuals exhibited significantly lower resting HRV (lower SDNN, RMSSD, NN50, pNN50) and higher heart rate compared to normal BMI individuals.
• Post-exercise, overweight participants showed persistently lower HRV parameters (SDNN, RMSSD, NN50, pNN50) and HF power.
• Overweight status was independently associated with lower RMSSD and HF power, and lower Physical Fitness Index (PFI).

Conclusions:

• Overweight young adults demonstrate reduced vagal-mediated HRV at rest and impaired autonomic recovery following exercise.
• RMSSD and SDNN are consistent HRV alterations that may serve as early markers of autonomic dysfunction in overweight youth.
• These findings highlight the importance of monitoring HRV for cardiovascular risk assessment in young adults with excess adiposity.