Standard Heart Rate Variability Parameters-Their Within-Session Stability, Reliability, and Sample Size Required to...

Area of Science:

• Physiology
• Biomedical Engineering
• Statistical Analysis

Background:

• Intervention studies often assume heart rate variability (HRV) parameter stability, yet small sample sizes can impact findings.
• Reliability and stability of HRV metrics are crucial for accurate interpretation of physiological responses to interventions.

Purpose of the Study:

• To assess the stability and reliability of standard HRV parameters within a single resting session.
• To estimate the sample size needed to detect clinically significant intervention effects on HRV.

Main Methods:

• Recorded heart rate in 50 healthy adults for 50 minutes in a seated position.
• Calculated eight standard HRV parameters from five 5-minute intervals.
• Assessed stability via test-retest measurements, absolute reliability using standard error of measurement, and relative reliability using intraclass correlation coefficient.

Main Results:

• Most HRV parameters exhibited poor absolute reliability but substantial to excellent relative reliability.
• Statistically significant differences were observed in most HRV parameters between the initial 20 minutes and the subsequent 30 minutes of the session.
• Estimated sample sizes ranged from 19-300 for the first 20 minutes and 36-194 for the 20-50 minute period.

Conclusions:

• Optimal HRV measurement in a resting seated position should occur within the first 20 minutes or between 20-50 minutes.
• Future intervention studies require sufficient sample sizes and consideration of Bonferroni correction for multiple HRV parameters to ensure power and precision.