Effects Of Shorter Blood Flow Restriction Cycles On Perceptual And Cardiovascular Responses

In the absence of exercise, blood flow restriction (BFR) can mitigate losses in muscle mass and strength following immobilization. However, a typical 5-min BFR protocol has been reported as painful, which may limit adherence. PURPOSE: To determine whether shorter and more frequent cuff inflations are a preferable alternative to the typical 5-min BFR protocol. METHODS: This is an ongoing study. Using a within-subject design, participants completed 4 visits. Visit 1 included familiarization. For visits 2-4, participants had 1 of 3 conditions applied on the dominant arm while supine: 5-min (BFR5, 5 cycles), 3-min (BFR3, 7 cycles), or 0-min (CON, 7 cycles) of cuff inflation at 80% arterial occlusion pressure (AOP). AOP was measured with an automated device, following an initial 5-min rest with the dominant arm abducted 90 degrees. Following a second 5-min rest, baseline ratings of pain and perceived discomfort were reported with separate 10-point scales. Heart rate (HR) and oxygen saturation (OSat) were measured with pulse oximetry. In the last 60 seconds of the last cuff inflation, participants reported their ratings of pain and perceived discomfort while HR and OSat were recorded. For statistical analysis, change scores (Δ, last cycle-baseline) were compared with one-way Bayesian Repeated Measures ANOVAs. Data is reported as mean ± standard deviation. RESULTS: Currently, 13 participants (22 ± 3 yr, 78.0 ± 12.7 kg, 171.2 ± 11.7 cm) have completed this study. ΔPain (A.U., BF10 = 1.949) was higher in BFR5 (1 ± 2) than both BFR3 (1 ± 1, BF10 = 1.026) and CON (0 ± 0, BF10 = 1.222). CON and BFR3 were similar (BF10 = 0.812). ΔDiscomfort (A.U., BF10 = 225.332) was higher for BFR5 (2 ± 2) than BFR3 (1 ± 2, BF10 = 2.362) and CON (0 ± 0, BF10 = 121.307). CON was lower than BFR3 (BF10 = 2.169). ΔHR (bpm, BF10 = 0.352) was similar across BFR5 (1 ± 5), BFR3 (0 ± 5), and CON (-1 ± 5). ΔOSat (%, BF10 = 8.772) was similar between BFR5 (-7 ± 8) and BFR3 (-8 ± 10, BF10 = 0.346). CON (1 ± 2) was higher than BFR5 (BF10 = 4.125) and BFR3 (BF10 = 3.874). ΔAOP (mm Hg, BF10 = 0.293) was similar across BFR5 (-1 ± 5), BFR3 (3 ± 13), and CON (1 ± 5). CONCLUSION: Our preliminary findings suggest that shorter cuff inflations with additional cycles may improve perceptions, and 3- or 5-min cycles elicit similar changes to the cardiovascular response.