Abstract
The present study was designed to investigate the effects of different caffeine dietary strategies to compare the impact on athletic performance and cardiac autonomic response. The order of the supplementation was randomly assigned: placebo(4-day)-placebo(acute)/PP, placebo(4-day)-caffeine(acute)/PC and caffeine(4-day)-caffeine(acute)/CC. Fourteen male recreationally-trained cyclists ingested capsules containing either placebo or caffeine (6 mg kg−1) for 4 days. On day 5 (acute), capsules containing placebo or caffeine (6 mg kg−1) were ingested 60 min before completing a 16 km time-trial (simulated cycling). CC and PC showed improvements in time (CC vs PP, Δ − 39.3 s and PC vs PP, Δ − 43.4 s; P = 0.00; ƞ2 = 0.33) and in output power (CC vs PP, Δ 5.55 w and PC vs PP, Δ 6.17 w; P = 0.00; ƞ2 = 0.30). At the final of the time-trial, CC and PC exhibited greater parasympathetic modulation (vagal tone) when compared to the PP condition (P < 0.00; ƞ2 = 0.92). Our study provided evidence that acute caffeine intake (6 mg∙kg−1) increased performance (time-trial) and demonstrated a relevant cardioprotective effect, through increased vagal tone.
Highlights
The present study was designed to investigate the effects of different caffeine dietary strategies to compare the impact on athletic performance and cardiac autonomic response
Since our study presented data from (1) procedures to ensure the control of experiments; (2) performance in TT-test; (3) heart rate variability (HRV) along and after the TT-test, the discussion was structured to follow the exposed sequence
The presence of foods, substances, supplements, or medicines containing CAF was not detected in the records, since blood analysis by HPLC confirmed no serum CAF concentration in athletes at the baseline, and after the supplementation, when submitted to placebo condition (i.e., PP)
Summary
The present study was designed to investigate the effects of different caffeine dietary strategies to compare the impact on athletic performance and cardiac autonomic response. On day 5 (acute), capsules containing placebo or caffeine (6 mg k g−1) were ingested 60 min before completing a 16 km time-trial (simulated cycling). Caffeine (1,3,7-Trimethylxanthine) is one of the most consumed supplements by both, general and athletes population[1] owing to an expected ergogenic effect for endurance e xercise[2], anaerobic-based e xercise[3] and strength/power activities. A primary role of adenosine in the nervous system appears to be to inhibit the release of various neurotransmitters, and possibly glutamate in particular, through presynaptic receptors. Adenosine antagonists, such as CAF, can be expected to increase the release of n eurotransmitters[10]. These changes may be related to high risks of cardiovascular events[11] especially during/ after exercise[12]
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