Relationship Between Heart Rate Variability And Resting Metabolism In Older Women

PURPOSE: To determine the relationship of resting metabolic rate (RMR) and heart rate variability (HRV) to body composition. METHODS: Forty-two older women, with an average age of 65 (4.3±) years, were included in this study. By means of electrical bioimpedance, using the base TANITA BC-601Fs was recorded weight, % body fat, % muscle mass, bone mass and BMI. The evaluation of the RMR was carried out with the Cosmed K5 metabolic car, according to the manufacturer the corresponding calibrations Flowmeter, Scrubber, Reference gas, Room air, Delay were performed, operating in the breath by breath mode. O2 and CO2 sensors measure the air composition with an approximate accuracy of < ± 3% (up to RF = 60/min); for 15 minutes. In compliance with the recommendations of the Working Group of the European Society of Cardiology and the North American Society for short-lived recordings of HRV, it was recorded in supine resting using a validated portable monitor (Polar H10 heart rate sensor, POLAR®, Kempele, Finland), connected to the HRV Elite application via Bluetooth 4.0. The HRV data was subsequently imported into the Kubios HRV standard 3.5.0. software to perform moderate smoothing and obtain the time domain interest variables, standard deviation from normal to normal intervals (SDNN); square root of the average square differences of successive normal-to-normal (RMSSD) intervals; NN50 ratio divided by the total number of NN (pNN50) intervals and frequency domain, low-frequency normalized units (LFnu), high- Frequency Normalized Units (HFnu) and the LF/HF ratio. It was carried out by regression and moderation analysis using SPSS statistical software (Version 4.2). RESULTS: Moderation analysis demonstrated the significant and negative indirect effect of muscle mass on HRV through REE (-0.0067) suggesting that, although directly muscle mass does not affect HRV, part of its influence is transmitted through the increase in REE. CONCLUSION: In older women, it is suggested that the relationship between muscle mass and HRV is mediated by REE. This finding indicates the existence of specific physiological mechanisms related to REE that impact HRV. Metabolic activity emerges as a fundamental element influencing how muscle mass relates to HRV.