Agreement Between a Smartphone Pulse Sensor Application and Electrocardiography for Determining lnRMSSD.

Area of Science:

• Sports Science
• Physiology
• Biomedical Engineering

Background:

• Heart rate variability (HRV) is a key indicator of physiological stress and recovery.
• Assessing HRV traditionally requires specialized equipment like electrocardiography (ECG).
• Emerging technologies aim to provide accessible HRV monitoring solutions.

Purpose of the Study:

• To evaluate the agreement between a smartphone pulse finger sensor (SPFS) and ECG.
• To determine accuracy in measuring ultra-short-term HRV, specifically lnRMSSD.
• To assess agreement across supine, seated, and standing body positions.

Main Methods:

• Simultaneous 60-second heart rate measurements using SPFS and ECG.
• Calculation of log-transformed root mean square of successive R-R interval differences (lnRMSSD).
• Comparison of lnRMSSD values and correlation analysis across three body positions in 30 participants.

Main Results:

• SPFS demonstrated strong correlations with ECG for lnRMSSD (r values 0.98-0.99).
• Good agreement was observed across all positions, with trivial effect sizes for differences in seated and standing positions.
• lnRMSSD values were comparable: ECG (81.5), SPFS (81.6) supine; ECG (76.5), SPFS (77.5) seated; ECG (66.5), SPFS (67.8) standing.

Conclusions:

• SPFS offers a valid and reliable method for measuring lnRMSSD.
• The findings support the use of smartphone applications for monitoring heart rate variability.
• SPFS provides a practical alternative to ECG for ultra-short-term HRV assessment in various postures.