A Practical Application of Blood Flow Restriction Exercise

Exercise with blood flow restriction (BFR) is emerging as an effective training option to increase muscle size and strength, in healthy, clinical, and athletic populations. However, the need for specialized equipment and associated costs present a major barrier to its accessibility. The purpose of this study was to develop a practical method to implement BFR in the lower body using a thigh sphygmomanometer. Specifically, we aimed to 1) explore what factors should be accounted for when setting pressures with this type of restrictive cuff and 2) generate both a lab-based and field-based prediction equation to estimate arterial occlusion pressure (AOP). We hypothesized that measures of limb size and blood pressure would constitute significant predictors of lower body AOP. We also hypothesized that a multiple linear regression model including significant predictors would explain approximately 50% of the variance in AOP. Thirty-eight normotensive healthy adults (age: 24±5 yrs, BMI: 25±4) visited the laboratory for one testing session. Brachial and femoral systolic (SBP) and diastolic (DBP) blood pressures were taken in the seated position. Next, thigh circumference, muscle thickness of the anterior thigh, and maximal isometric knee extension strength was assessed. Lean thigh volume was estimated using anthropometric measures. Lastly, lower body AOP was assessed in the seated position using an 18cm wide thigh sphygmomanometer and Doppler ultrasound (156±12 mmHg). A multiple linear regression analysis including brachial and femoral SBP and DBP, thigh circumference, muscle thickness, lean thigh volume, and maximal isometric knee extension strength was performed to assess which variables constituted significant predictors of AOP. Regression analysis was then repeated with only significant variables to generate both a lab-based and field-based prediction equation for AOP. Thigh circumference (β = 0.322, part = 0.876), brachial SBP (β = 0.362, part = 0.463) and isometric knee extension strength (β = 0.421, part = 0.076) constituted significant predictors of AOP. A lab-based model including thigh circumference (β=0.278, part = 0.754), brachial SBP (β=0.492, part = 0.549), and isometric knee extension strength (β=0.306, part = 0.055) explained 56% of the variance in AOP. A field-based model including only thigh circumference (β=0.316, part = 0.857) and brachial SBP (β=0.515, part = 0.658) explained 47% of the variance in AOP. Our results indicate that thigh circumference, brachial SBP, and isometric knee extension strength serve as predictors of AOP in the lower body when utilizing an 18cm wide sphygmomanometer as a restrictive cuff. Further, a field-based prediction equation including thigh circumference and brachial SBP offers a practical way to estimate AOP. Future work will build upon this prediction equation by utilizing subjective measures of cuff tightness, effort, and muscle pain to further adjust exercising cuff pressures to an appropriate level. Results will help to provide researchers and practitioners with a practical way to implement BFR without the need for specialized equipment.