Caffeine Abstinence In Habituated Users: Cardiovascular And Perceptual Responses To Exercise With Blood Flow Restriction

Abstract

Studies using blood flow restriction resistance exercise (BFR-RE) often require caffeine abstinence. For habitual users,effects may be attenuated, and it is unknown if abstinence alters responses to BFR-RE. PURPOSE: Compare cardiovascular and perceptual responses to BFR-RE when habitual users consume or abstain from caffeine. METHODS: 15 participants completed a 3 visit within-subject study beginning with a one repetition maximum (1RM) test and caffeine intake assessment. Visits 2-3 consisted of dominant arm BFR-RE [3 sets of bicep curls to failure with 30% 1RM, 40% arterial occlusion pressure (AOP), 30s inter-set rest]. Visits 2-3 were 1h after typical dose, one with caffeine (CAFF) and one without (ABS) (counterbalanced). Heart rate (HR), systolic (SBP) and diastolic (DBP) BP, and AOP were measured pre- and post-exercise and ratings of perceived exertion (RPE-E) and discomfort (RPE-D) after each set. Exercise volume(VOL) per set was calculated as load (kg) x repetitions. Bayesian RMANOVA were used to find the most probable model for SBP, DBP, HR and AOP (results are mean ± SD). BF10 = most probable alternative model vs. the null. Bayesian paired t-tests were used to compare RPE-E, RPE-D, and VOL for each set (results are mean difference ± SD). RESULTS: Main effects of time and condition for SBP (mmHg, BF10 = 895.4) and DBP (mmHg, BF10 = 481.6) indicated CAFF (SBP = 118.4 ± 10.9, DBP = 82.3 ± 10.4) was greater than ABS (SBP = 114.6 ± 10.6, DBP = 79.2 ± 9.9), and post (SBP =119.9 ± 11.0, DBP = 8.6 ± 11.4) was greater than pre (SBP = 113.1 ± 9.6, DBP = 76.93 ± 7.1). A main effect of time indicated AOP (mmHg, BF10 = 10390.7) increased pre (134.5 ± 16.5) to post (150.5 ± 20.6). A main effect of time indicated HR (bpm, BF10 = 50.5) increased pre (80.1 ± 10.1) to post (87.7 ± 14.0). Moderate evidence indicated no difference in RPE-E (AU) between CAFF and ABS for set 1 (0.0 ± 0.9, BF10 = .3) and anecdotal evidence for sets 2 (0.3 ± 1.2) and 3 (-0.3 ± 1.2, BF10 both ≤.4). Anecdotal evidence indicated no difference in RPE-D (AU) between CAFF and ABS for sets 1 (0.0 ± 1.2), 2 (0.3 ± 1.9), and 3 (-0.4 ± 1.7, BF10 all ≤.4). Anecdotal evidence indicated no difference in VOL (AU) for sets 1 (6.1 ± 24.4), 2 (-0.2 ± 10.6), and 3 (-0.5 ± 7.3, BF10 all ≤.4). CONCLUSION: In habitual users, caffeine may increase BP, but other cardiovascular and perceptual responses to BFR-RE may not be impacted.