Cardiac autonomic function and high-intensity interval training in middle-age men

Area of Science:

• Exercise Physiology
• Cardiovascular Health
• Autonomic Nervous System Function

Background:

• The impact of short-term high-intensity interval training (HIT) on cardiac autonomic function remains incompletely understood.
• This study aimed to compare the cardiac autonomic adaptations induced by short-term HIT versus aerobic endurance training (AET).

Purpose of the Study:

• To assess and compare the effects of short-term HIT and AET on cardiac autonomic function in healthy middle-aged men.
• To investigate changes in heart rate variability (HRV) parameters, including low-frequency (LF) and high-frequency (HF) power, following these training interventions.

Main Methods:

• Twenty-six sedentary middle-aged men were randomized into HIT (n=13) or AET (n=13) groups for a 2-week intervention (6 sessions).
• Participants underwent 24-hour ECG monitoring pre- and post-intervention, with daily morning supine R-R interval recordings.
• Analysis included mean heart rate (HR), 24-hour LF and HF power, and daytime HF power.

Main Results:

• Both HIT and AET increased peak oxygen consumption (V˙O2peak).
• HIT significantly increased 24-hour LF power and daytime HF power compared to AET.
• Home-based supine HF power decreased on days following HIT sessions, indicating an acute autonomic response.

Conclusions:

• Short-term HIT is a more effective strategy than AET for enhancing R-R interval variability, likely through increased cardiac vagal activity.
• The acute autonomic responses to individual HIT sessions did not show adaptation within the short 2-week training period.