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Time‐Released Caffeine Ingestion in Habitual Users May Extend Parasympathetic Influence as Determined by Heart Rate Variability
Author(s) -
La Monica Michael B,
Fukuda David H,
Gonzalez Adam M,
Wang Ran,
Wells Adam J,
Stout Jeffrey R,
Hoffman Jay R
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.843.15
Subject(s) - caffeine , heart rate variability , supine position , heart rate , placebo , medicine , autonomic nervous system , anesthesia , cardiology , blood pressure , alternative medicine , pathology
Heart rate variability (HRV) is a noninvasive method of identifying vagal and sympathetic control of heart rate via time‐domain and frequency‐domain measures. Caffeine has shown to enhance autonomic responsiveness by increasing parasympathetic influence, however a time‐release caffeine supplement has not yet been investigated. OBJECTIVE To determine the effects of a time‐release caffeine supplement on HRV over 8 hours. METHODS Ten men (25.9 ± 3.2 y; 1.81 ± 0.08 m; 92.9 ± 9.9 kg), who were habitual caffeine users (>200mg/day), volunteered to participate in an acute randomized, double‐blind, placebo‐controlled study. Participants performed three trials with seven days between each trial. During each trial, participants randomly consumed either 194 mg of caffeine in a multi‐ingredient supplement containing time‐release caffeine (TR‐CAF); a regular caffeine supplement (CAF); or a placebo (PL). Participants reported to the lab at 0800 hour following an 8‐hour fast and having abstained from caffeine. HRV was assessed for 10 min via Polar heart rate monitor with the participant lying in the supine position during baseline, before supplementation, and each hour during each 8 hour trial. Time‐domain [mean standard deviation of all normal‐to‐normal (NN) intervals (SDNN in ms), root mean square of differences between adjacent NN intervals (RMSSD in ms), the number of pairs of adjacent NN intervals differing by more than 50 ms within the entire recording (NN50), the proportion of NN50 count relative to the total number of all NN intervals (pNN50)] and frequency‐domain [low frequency (LF in ms 2 ), high frequency (HF in ms 2 ), total power (in ms 2 ), LF/HF, an index of parasympathetic nervous system (PNS=HF/total power) measures were recorded. A two‐way [trial (CAF vs. TR‐CAF vs. PL) × time (BL, 1hr, 2hr, 3hr, 4hr, 5hr, 6hr, 7hr, 8hr)] RMANOVA was used to assess all HRV parameters. RESULTS A significant interaction was noted for PNS ( p = .045). Post‐hoc analyses revealed elevations in PNS influence occurred in both TR‐CAF (0.27 ± 0.12, p = .045) and CAF (0.29 ± 0.16, p = .009) compared to PL (0.18 ± 0.08) at hour 6 and hour 7 in TR‐CAF (0.34 ± 0.15, p = .018) compared to PL (0.23 ± 0.13). There were significant main effects of time for RMSSD ( p = .021) and pNN50 ( p = .012). DISCUSSION Both caffeine supplements increased parasympathetic influences within the autonomic nervous system over an 8‐hour span. However, the time‐release caffeine supplement appeared to have a slightly longer lasting effect on parasympathetic influence than regular caffeine. Overall, caffeine in the concentrations ingested in this study increases vagal stimulation, but has no effect on other elements of HRV in habitual caffeine users.