Purpose: The purpose of this study was to investigate the blood flow/pressure relationship (linear or nonlinear) in the superficial femoral artery when seated, as well as to investigate blood flow changes with exercise using varying cuff pressures and a preexercise (PE) condition. The presence of venous outflow with occlusion at rest and exercise was also investigated.Methods: Twenty-three subjects visited the lab on 3 occasions. First to determine linearity of blood flow using 0% to 90% arterial occlusion pressure (AOP), and venous outflow at rest and during exercise with cuff inflated to 40% AOP. Subsequent visits compared blood flow between rest and PE conditions to determine average blood flow, heart rate, systolic and diastolic blood pressure changes in response to a blood flow-restricted (BFR) exercise protocol. Results: Blood flow/pressure relationship is nonlinear at the superficial femoral artery (p < 0.01). No significant differences in average blood flow, conductance or mean arterial pressure (MAP) were found between 30% to 80% AOP (p = 1.0 to .08). Blood flow is not significantly different between rest and PE groups (p = 0.49) although initial 40% AOP and 40% exercise arterial occlusion pressure (EAOP) values were different between rest and PE groups. (p < 0.01). Conclusion: The nonlinear relationship at the superficial femoral artery demonstrates higher cuff pressures are not necessary to reduce blood flow in BFR exercise of the lower extremity. Furthermore, PE or warm-up is not necessary prior to determining EAOP as it does not alter blood flow responses during BFR exercise. We found evidence of venous outflow above the cuff both at rest and during exercise at 40% AOP.

PURPOSE: This study comparted arterial occlusion pressure (AOP) of the superficial femoral artery (SFA) between the dominant and nondominant legs and the relationship between blood flow and occlusion pressure at rest and during muscle contractions in males and females. METHODS: The AOP of the SFA was measured using Doppler ultrasound in the dominant and nondominant legs of 35 (16 males, 19 females) apparently healthy, normotensive young adults. Blood flow in the SFA was measured in the resting state (REST) and during plantar flexion exercise (EXC) at occlusion pressures ranging from 0% to 100% of AOP. ANOVA was used to compare AOP between the dominant and nondominant legs and between males and females. Regression analysis was used to evaluate the influence of relevant variables on AOP. A mixed model was used to evaluate the relationship between blood flow and occlusion pressure at REST and during EXC. RESULTS: There was a significant difference in the AOP between the dominant and nondominant legs in males (230 ± 41 vs 209 ± 37 mmHg) and females (191 ± 27 vs 178 ± 21 mmHg), respectively. There was also a significant sex difference in the AOP in the dominant (230 ± 41 vs 191 ± 27 mmHg; p = 0.002) and nondominant (209 ± 37 vs 178 ± 21 mmHg; p = 0.004) legs, respectively. Regression analysis revealed that after accounting for leg circumference, age, sex, blood pressure, and skinfold thickness were not independent predictors of AOP. At REST and during EXC, there was a linear relationship between relative blood flow and occlusion pressure. CONCLUSIONS: Differences in leg circumference contribute to a portion of the differences in AOP between the dominant and nondominant legs and between sexes. The linear relationship between relative blood flow and occlusion pressure suggests that occlusion pressures during blood flow restriction exercise should be chosen carefully. A large variance in blood flow measurements at different occlusion pressures suggests the need for evaluating the reliability of blood flow measurements and standardization of methods.