Effects of Caffeine Supplementation on Short-term Heart Rate Variability

Caffeine is present in many commonly consumed beverages, and the effect of caffeine on one's autonomous nervous system is of considerable interest. The time taken for caffeine to act on the body varies from person to person. This study is aimed to see the short-term effects of caffeine supplements (200 mg/capsule) on Heart Rate Variability (HRV) considering this individualised response to caffeine. Thirty healthy subjects participated in the study (Female:10, Male:20, Age:24.60 ± 3.02). The ECG data of the subjects were collected using the platform 'Repose' by Netrin Sports Technologies, India. The duration after the caffeine intake of two hours was divided into smaller time windows (30mins) to closely observe how HRV changed. The study used Kubios Standard software (version 3.5.0) to analyse time-domain HRV parameters, frequency-domain HRV parameters and autonomic nerve indexes before and after the intervention. Questionnaires were used to understand the subjects' caffeine tolerance and habits and to understand the subjects' psychological state during the study. It was found that the subjects' parasympathetic activity improved after caffeine intake, resulting in better HRV parameters and autonomic nerve indexes. The HRV was found to peak after a particular time post the intake, and this time varied from person to person. Statistically significant changes were observed in RMSSD, pNN50, HR, LF/HF, SI and PNS after caffeine intake (p<0.05). No significant changes were found in SDNN.