Title

Maintenance of Vagal Tone with Time-Release Caffeine, But Vagal Withdrawal During Placebo in Caffeine-Habituated Men

Document Type

Article

Publication Date

2018

Abstract

Objective: This study aimed to determine the effects of a time-release caffeine (TR-CAF) supplement and caffeine abstinence on heart rate variability (HRV) in habitual users. Methods: Ten caffeine-habituated (>200 mg per day) men (25.9 ± 3.2 years; 1.81 ± 0.08 m; and 92.9 ± 9.9 kg) performed three trials, each separated by 1 week. During each trial, participants randomly consumed either 194 mg of caffeine in a multi-ingredient supplement containing TR-CAF; an instant-release caffeine supplement (CAF); or placebo (PL). HRV was assessed for 10 minutes in the supine position at baseline (BL), and every hour after supplementation for 8 hours. Time-domain [average heart rate, mean standard deviation of all normal-to-normal (NN) intervals (SDNN), and root mean square of differences between adjacent NN intervals (RMSSD)] and frequency-domain [low frequency (LF), high frequency (HF), total power (TP), LF/HF, and an index of parasympathetic nervous system (PNS = HF/TP)] measures were recorded. A two-way (trial × time) repeated-measures analysis of variance was used to assess all HRV parameters. Results: A significant interaction was noted for PNS (p = 0.039). There was a significant difference between trials 1-hour post-ingestion, but post hoc analysis noted a trend between CAF and PL (p = 0.079). However, at 6 hours, post-ingestion post hoc analyses revealed higher PNS influence during both TR-CAF (0.84 ± 0.06, p = 0.039) and CAF (0.84 ± 0.07, p = 0.005) compared to PL (0.79 ± 0.05). There was a significant main effect of time for PNS index during the PL condition only, but no subsequent differences were noted from BL in post hoc analyses. Conclusions: Both caffeine supplements maintained parasympathetic influence within the autonomic nervous system, while PL appeared to result in the potential for vagal withdrawal over an 8-hour span.

Recommended Citation

La Monica, Michael B., David H. Fukuda, Ran Wang, Adam M. Gonzalez, Adam J. Wells, Jay R. Hoffman, and Jeffrey R. Stout. "Maintenance of Vagal Tone with Time-Release Caffeine, But Vagal Withdrawal During Placebo in Caffeine-Habituated Men." Journal of Caffeine and Adenosine Research 8, no. 2 (2018): 59-64.

DOI for the article

10.1089/caff.2017.0039

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