BACKGROUND: Blood flow restriction (BFR) has been used to delay muscle atrophy, but it is unclear how this impacts the vasculature. The purpose of this study was to determine chronic effects of BFR on upper body vasculature. METHODS: 40 participants were randomized into control (CON) or BFR. For BFR, 80% of arterial occlusion pressure (AOP) was applied 5 days/week for 5 cycles (5min inflation, 3min deflation) on the dominant arm. Vascular assessments occurred at baseline (Pre), week 1 (Mid), and week 2 (Post). A cuff on the forearm was inflated (≥110% AOP) for 5min while brachial artery diameter and tissue saturation index (TSI, %) were continuously measured. Flow mediated dilation (FMD) was calculated as maximal artery diameter following cuff deflation minus resting diameter. TSI slope 1 (S1, %/s) included 60s during initial cuff inflation, S2 (%/s) included 15s after deflation, and area under the curve (AUC, %∙s) included 180s after deflation. Acute muscle thickness changes (via ultrasound, ΔMuTh, cm) and pain (via visual analog scale, VAS, A.U.) were measured on the first and last BFR sessions. Vascular variables were compared with Bayesian RMANOVAs (BF10=likelihood of the interaction model vs the null), ΔMuTh was compared with Bayesian One-way RMANOVA and VAS was compared with Bayesian paired samples T-Test. Results presented as mean±SD. RESULTS: Null model was most likely for all vascular variables. Dominant arm FMD (Pre: BFR .03±.01, CON .03±.01; Post: BFR .03±.01, CON .03±.02; BF10=.017) was similar between conditions and time points. S1 (Pre: BFR -.07±.04, CON -.07±.04; Post: BFR -.08±.03, CON -.07±.03; BF10=.064), S2 (Pre: BFR 1.66±1.07, CON 1.79±.89; Post: BFR 1.96±.68, CON 1.79±.78; BF10=.016), AUC (Pre: BFR 13330±968, CON 13348±939; Post: BFR 13509±668, CON 13470±870; BF10=.005), and minimum TSI during cuff inflation (Pre: BFR 51.6±9.8, CON 51.0±10.7; Post: BFR 50.1±8.8, CON 51.4±8.1;BF10=.006) were similar between conditions and time points. ΔMuTh changed with time (BF10=3.952). First session (-.01±.11) was smaller than second (.09±.14; BF10=1.809) and last (.06±.08; BF10=2.393), but second and last (BF10=.319) were similar. Maximum VAS was similar across sessions (first: 3.9±2.6, last: 3.0±2.6; BF10=.552) with a similar trend for mean VAS. CONCLUSIONS: Two weeks of BFR may be tolerable, but does not alter vasculature, muscular swelling, or become less painful in healthy untrained participants.

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