Brianna N. Cupp, Daphney M. Stanford, Matthew A. Chatlaong, Matthew B. Jessee. The University of Mississippi, University, MS.

BACKGROUND. Blood flow restriction (BFR) alone decreases muscle atrophy following immobilization. It is unknown what effect BFR alone has on microvasculature. The purpose of this study is to determine the acute effect of BFR alone on oxygen extraction rate (Slope 1, S1) and reactive hyperemia (Slope 2, S2) when compared to a protocol known to improve vascular function. METHODS. 9 females and 11 males (height: 164.2±21.1 cm; weight: 72.7±29.0 kg; age: 27.6±10.6 y) completed 3 protocols (separate visits), on the right arm, while supine. For all conditions a cuff was secured on the upper arm. First, after a 5min rest, AOP was measured. After another 5min rest, the protocol started. For control (CON), the cuff remained deflated. For BFR, a cuff was inflated to 80% arterial occlusion pressure (AOP) for 5 cycles (5min inflation/3min deflation). For ischemic preconditioning (IPC), a cuff was inflated to 105% AOP for 4 cycles (5min inflation/5min deflation). A near-infrared spectroscopy device (NIRS) continuously estimated deoxy(Hb, µM∙s-1)/oxy(O2,µM∙s-1) heme and tissue saturation index (TSI, %∙s-1) at the forearm. S1 was the 60s following cuff inflation and S2 was the 30s immediately after cuff deflation. The regression slopes from each cycle were averaged and compared across conditions with Bayesian RMANOVA. Results presented as mean±SD. BF10=likelihood of the best model vs the null. RESULTS. S1 for TSI (Condition: BF10=4.518e+13) was steeper in BFR (-0.07±0.04) when compared to CON (0.01±0.01; BF10=202810.265), but flatter than IPC (-0.10±0.03; BF10=7.330). IPC was steeper compared to CON (BF10= 1.524e+8). S1 for O2 (Condition: BF10=6.682e+11) was positive and steeper in BFR (0.17±0.11) than CON (0.01±0.01; BF10=24409.937) and IPC (-.05±0.07; BF10=407178.004). IPC was negative compared to CON (BF10=32.242). S1 for Hb (Condition: BF10=3.856e+22) was positive and steeper in BFR (0.21±0.05) than CON (-0.01±0.0; BF10=4.626e+10) and IPC (0.15±0.05; BF10=226.453). IPC was positive compared to CON (BF10=3.097e+9). TSI for S2 (Condition: BF10=7.977e+15) was steeper for BFR (0.76±0.30; BF10=1.495e+7) and IPC (1.06±0.39; BF10=3.947e+7) compared to CON (0.0±0.01). BFR was typically flatter than IPC (BF10=42.285). CONCLUSION. The current data suggests BFR has a lower extraction rate and hyperemic response than IPC. Chronic application of BFR alone may elicit vascular adaptations, but the magnitude may be lower than IPC.

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