The effects of varying doses of caffeine on cardiac parasympathetic reactivation following an acute bout of anaerobic ex

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RESEARCH ARTICLE

(2020) 17:44

Open Access

The effects of varying doses of caffeine on cardiac parasympathetic reactivation following an acute bout of anaerobic exercise in recreational athletes Amir Sarshin1*, Alireza Naderi2 , Carlos Janssen Gomes da Cruz3, Foad Feizolahi1, Scott C. Forbes4, Darren G. Candow5, Ebrahim Mohammadgholian1, Mehrdad Amiri1, Naghmeh Jafari1, Alireza Rahimi1, Eidi Alijani1 and Conrad P. Earnest6

Abstract Background: To examine the effects of varying doses of caffeine on autonomic reactivation following anaerobic exercise. Methods: Recreationally active males (N = 20; 24 ± 2y) participated in a randomized, double-blind, placebocontrolled, crossover study where participants ingested: [1] Control (CON; no supplement), [2] a non-caffeinated placebo (PLA), [3] 3-mg∙kg− 1 of caffeine (CAF3) or [4] 6-mg∙kg− 1 of caffeine (CAF6) prior to Wingate testing. Parasympathetic (lnRMSSD, primary outcome) and global HRV (lnSDNN, secondary outcome) were assessed at rest (i.e., pre-ingestion), 45-min post-ingestion, and 5-min and 35-min post-exercise recovery. We used a GLM to assess mean (95% CI) changes from pre-ingestion baseline. Results: Overall, we observed a significant trend for lnRMSSD and lnSDNN (both, p = 0.001, ηp2 = 0.745). Forty-five minutes after treatment ingestion, we observed a significant increase in lnRMSSD for CAF3 (0.15 ms, 95%CI, 0.07, 0.24) and CAF6 (0.16 ms, 95%CI, 0.06,0.25), both being significant (both, p < 0.004) vs. CON (− 0.02 ms, 95%CI, − 0.09, 0.04). Five-minutes after exercise, all treatments demonstrated significant declines in lnRMSSD vs. baseline (all, p < 0.001). After 35-min of recovery, lnRMSSD returned to a level not significantly different than baseline for CAF3 (0.03 ms, 95%CI, − 0.05, 0.12) and CAF6 (− 0.03 ms, 95%CI, − 0.17, 0.10), while PLA (− 0.16 ms, 95%CI, − 0.25, − 0.06) and CON (− 0.17 ms, 95%CI, − 0.28, − 0.07) treatments remained significantly depressed. A similar pattern was also observed for SDNN. Conclusion: Caffeine ingestion increases resting cardiac autonomic modulation and accelerates post-exercise autonomic recovery after a bout of anaerobic exercise in recreationally active young men. However, no differences between caffeine doses on cardiac autonomic reactivity were observed. Keywords: Exercise, Caffeine, Anaerobic performance, Dietary supplement, Heart rate variability, Autonomic balance

* Correspondence: [email protected] 1 Department of Exercise Physiology, Karaj Branch, Islamic Azad University, Karaj, Iran Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article'