Autonomic Function Predicts Fitness Response to Short-Term High-Intensity Interval Training.

Area of Science:

• Exercise Physiology
• Autonomic Nervous System Function
• Cardiovascular Regulation

Background:

• Individual responses to exercise training vary significantly.
• Cardiac autonomic function, reflecting sympathovagal balance, may influence adaptation to training.
• Understanding predictors of training response is crucial for personalized exercise prescription.

Purpose of the Study:

• To investigate if baseline cardiac autonomic function and its acute response to exercise predict individual fitness adaptations to high-intensity interval training (HIT).
• To compare these predictive relationships between HIT and traditional aerobic endurance training (AET).

Main Methods:

• Healthy middle-aged sedentary men underwent 2 weeks of either HIT or AET.
• Cardiac autonomic function was assessed using heart rate variability (HRV) analysis (LF/HF ratio) in supine and standing positions.
• Training outcomes (workload capacity and peak oxygen consumption) were measured before and after the intervention.

Main Results:

• Both HIT and AET significantly improved exercise capacity and peak oxygen consumption.
• Pre-training supine LF/HF ratio (sympathovagal balance) correlated with improvements in workload and VO2peak in the HIT group, but not AET.
• Changes in standing LF/HF ratio following acute HIT exercise also correlated with training outcomes in the HIT group.

Conclusions:

• Baseline cardiac sympathovagal balance is a significant predictor of fitness response to short-term HIT in sedentary men.
• The acute response of cardiac autonomic function to initial HIT sessions further relates to subsequent training adaptations.
• These findings suggest that autonomic function plays a key role in individualizing HIT programs.