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Article Title

COMPARING POST-OCCLUSIVE REACTIVE HYPEREMIA IN HABITUAL CAFFEINE USERS WHEN CONSUMING AND ABSTAINING FROM CAFFEINE

Abstract

Chance J. Davidson, Matthew A. Chatlaong, Daphney M. Stanford, Matthew B. Jessee. University of Mississippi, University, MS.

BACKGROUND: Since caffeine affects cardiovascular responses, studies measuring post-occlusive reactive hyperemia (PORH) commonly require caffeine abstinence. For habitual users, effects may be attenuated, and it is unknown if abstinence alters PORH. PURPOSE: Compare PORH in habitual caffeine users when they consume or abstain from daily caffeine intake. METHODS: 28 participants completed a 3 visit within-subject study. Visit 1 consisted of familiarization and caffeine intake assessment. Visits 2-3 (1h after typical dose) consisted of PORH measures, one with (CAFF) and one without (ABS) typical caffeine doses (counterbalanced). Beginning of visits 2-3, arterial occlusion pressure (AOP) was measured via handheld Doppler probe. Heart rate (HR), systolic (SBP), and diastolic (DBP) blood pressure were measured simultaneously on the opposite arm. Testing consisted of 2 min of baseline, followed by 5 min of cuff inflation at 130% AOP, then 3 min of PORH measured with Doppler ultrasound and near-infrared spectroscopy (NIRS). Peak hyperemic velocity was the highest value of a 3s moving average after cuff deflation. Baseline velocity was the average of the 2 min period. NIRS tissue saturation index rate of change during ischemia (Slope 1) and for 30s after cuff deflation (Slope 2) was quantified via linear regression. Bayesian paired t tests were used to compare all variables between conditions. BF10= likelihood of alternative vs null. Results are mean±SD. RESULTS: There was moderate evidence that baseline velocity was the same for CAFF (9.3±4.8) and ABS (7.5±4.9, BF10=1.0). There was moderate evidence that peak hyperemic velocity (cm/s) was the same for CAFF (77.3±16.7) and ABS (77.6±19.0, BF10=.20). There was moderate evidence that Slope 2 (%/s) was the same for CAFF (1.9±.46) and ABS (1.8±.42, (BF10=.20). There was moderate evidence that Slope 1 was the same for CAFF (-.11±.04) and ABS (-.12±.03, (BF10=.20). There was moderate evidence that SBP (mmHg) was the same for CAFF (116.0±9.8) and ABS (115.5±10.7, (BF10=.220). For DBP (mmHg) evidence was weak (BF10=1.1) when comparing CAFF (69.6±5.8) and ABS (69.5±5.4). For AOP (mmHg) evidence was weak (BF10=.46) when comparing CAFF (146.6±15.0) and ABS (143.0±16.4). There was moderate evidence that HR (bpm) was the same for CAFF (66.5±12.3) and ABS (66.9±13.0, BF10 =.2). CONCLUSION: In habitual users, consuming typical caffeine doses does not appear to affect post-occlusive reactive hyperemia.

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