Heart rate variability in physically active individuals: reliability and gender characteristics.

Area of Science:

• Physiology
• Sports Science
• Cardiovascular Research

Background:

• Heart Rate Variability (HRV) is a non-invasive measure reflecting autonomic nervous system activity.
• Assessing HRV reliability is crucial for interpreting physiological responses to training and interventions.
• Understanding gender-specific HRV patterns can elucidate sex-based differences in cardiovascular regulation.

Purpose of the Study:

• To determine the relative and absolute reliability of short-term (five-minute) HRV recordings.
• To investigate the association between HRV parameters and gender in physically active students.

Main Methods:

• HRV time- and frequency-domain parameters were analyzed over four days in 44 students (21 males, 23 females) using a Suunto t6 monitor and Kubios HRV software.
• Relative reliability (Intra-class Correlation Coefficient - ICC) and absolute reliability (Typical Error of Measurement - TEM, TEM%) were calculated.
• Analysis of Variance (ANOVA) was used to compare HRV parameters between genders.

Main Results:

• High relative reliability (ICC > 0.8) was observed for most HRV parameters, except for the LF/HFnu ratio.
• Absolute reliability was generally low (TEM% > 10%) for most parameters, indicating significant day-to-day variability.
• Females showed better reliability for frequency-domain parameters and significant differences in LF/HFnu, HFnu, and IBI compared to males.

Conclusions:

• Short-term HRV recordings offer high relative reliability but low absolute reliability, limiting the detection of individual changes.
• Females exhibit greater parasympathetic modulation of HRV, potentially indicating a cardioprotective mechanism.
• Gender differences in HRV parameters warrant consideration in research and clinical applications.