Endurance performance and nocturnal HRV indices.

Area of Science:

• Exercise Physiology
• Cardiovascular Autonomic Function
• Sports Science

Background:

• Endurance training enhances athletic performance.
• Cardiac autonomic modulation, particularly vagal activity, plays a role in cardiovascular health and recovery.
• Understanding the relationship between training adaptations and autonomic responses is crucial for optimizing performance.

Purpose of the Study:

• To investigate the impact of a 4-week endurance training program on endurance performance.
• To examine changes in cardiac autonomic modulation during sleep following training.
• To determine if improvements in performance correlate with autonomic nervous system adaptations.

Main Methods:

• Twenty-four sedentary subjects underwent 4 weeks of supervised endurance training.
• Maximal velocity (v(max)) was assessed using an incremental treadmill test.
• Heart rate variability (HRV) indices, including high frequency power (HFP), were analyzed from ECG recordings during sleep.

Main Results:

• Subjects were categorized into responders and non-responders based on v(max) improvement.
• Responders showed a significant increase in v(max) (10.9%), while non-responders did not (1.6%).
• Nocturnal high frequency power (HFP) significantly increased in responders by the fourth week and correlated with v(max) improvements.

Conclusions:

• Endurance training can improve maximal running velocity in previously sedentary individuals.
• Enhanced cardiac vagal modulation during sleep is associated with greater improvements in endurance performance.
• Autonomic nervous system adaptation is a key factor in the physiological response to endurance training.