The Effect of Postural Position on Arterial Occlusion Pressure in the Lower Body: A Methodological Consideration for Blood Flow Restriction Training.

INTRODUCTION: Low intensity resistance training, with partial blood flow restriction (BFR), has repeatedly shown increases in both muscle size and strength. Despite the growing interest in BFR, there lacks a consensus regarding its methodological application. Perhaps one of the most obvious and overlooked considerations with BFR is postural position. Many reports have demonstrated significant haemody- namic changes with postural position but few BFR studies have considered this. Therefore, it is suggestible that arterial blood flow differs between position when under restriction and that previous studies have large variations in the level of BFR. Fundamental haemodynam- ics are largely influenced by gravitational forces exerting hydrostatic pressures within blood vessel. We hypothesised that arterial occlu- sion pressure (AOP) would be significantly higher when seated due to gravitational-induced hydrostatic pressure seen with upright haemodynamics. METHODS: Twenty participants (15 Male & 5 Female) visited the laboratory for one testing session. Basic anthropometric data were meas- ured including height, mass and thigh circumference. Systolic (SBP) and diastolic (DBP) brachial pressures were measured using an automatic blood pressure cuff. A 14.5 cm wide cuff (Delfi Medical, Vancouver BC, Canada) was then placed around the most proximal portion of the right leg. Arterial blood flow was measured at the posterior tibial artery using audio and visual signals from a handheld Doppler probe (Esaote MyLab 25cv). The cuff was inflated to 50mmHg for 30 s and then deflated for a 10 s interval to familiarise subjects. The cuff was then inflated to the participants brachial SBP for 30 s and deflated for 10 s. Following these initial inflation periods, pressure was increased by 40 mmHg for 30 s with 10 s deflation period. This was repeated until arterial blood flow was no longer detected from which point pressure was decreased by 10mmHg until arterial flow was present. The AOP was recorded as the last 10mmHg where blood flow was not detect- ed.The above procedures were repeated after 5 min rest period in an upright-seated position. RESULTS: Seated AOP was significantly higher than when supine (p < 0.001, 24±11.8mmHg). Regression analysis revealed thigh circum- ference and diastolic blood pressure were significant predictors of supine AOP (p = 0.001, r2 = 0.55), but not seated AOP; height was the only significant predictor of seated AOP (p = 0.017, r2 = 0.277). CONCLUSION: In conclusion, AOP was significantly greater when seated with height accounting for 27% of the variance. This suggests that gravity induced-hydrostatic pressure and the height of the hydrostatic column significantly alter the AOP. In future, postural position should be considered when utilising BFR training. Using thigh circumference and diastolic blood pressure, we are able to estimate supine AOP with a 14.5cm cuff, but not seated AOP. Based on our findings, we conclude that postural position significantly effects arterial occlusion pressure.