B-25 Free Communication/Poster - Balance and Flexibility

Abstract

The transient increase in femoral artery blood flow (BF) during passive knee extension and flexion has been well established. With the absence of neural drive and metabolic byproducts the hyperemic response is believed to be due to cardio-acceleration via activation of type III fibers, mechanically induced vasodilation and muscle pump activity. However, the cardiovascular responses to passive limb movement (PLM) in the upper body and with smaller muscle mass have not been established. PURPOSE: To determine if the hyperemic response to PLM is consistent between limbs in the upper and lower body. METHODS: Sixteen participants underwent a PLM protocol in which the wrist, elbow, ankle and knee joints were passively extended and flexed at 1Hz for 60 seconds. HR, MAP and BF were measured and conductance (CON) calculated for a 30 second baseline period and throughout the 1 minute PLM bout. BF measurements for the wrist, forearm, ankle and knee were obtained by Doppler ultrasound measurements of the brachial, subclavian, popliteal and femoral arteries, respectively. Results were averaged into three second blocks for data analysis. Paired samples t-tests were used to determine if the relative changes in BF, HR and CON were different between limbs. RESULTS: Passive movement of all joints resulted in significant increases in BF, HR and CON from baseline (p<.05). Passive knee movement resulted in a blood flow increase of 296 ml/min (+211%) which was significantly greater than the response of the wrist (27.6 ml/min, +49.9%, p=0.03) and ankle (36.9 ml/min, +69.4%, p=0.01) but not for the elbow (52.4 ml/min, 75.7%, p=0.07). Similarly, no significant differences between changes in HR (p=0.8) and CON (p=0.08) were observed between the knee and elbow, but the knee showed greater changes in HR and CON compared to wrist (p=0.04 and p=0.04) and ankle (p=0.01 and p=0.01), respectively. CONCLUSIONS: PLM of the ankle and wrist resulted in similar increases in BF, HR and CON but not to the extent of the knee and elbow. The reduced response with PLM of wrist and ankle is likely due to reduced muscle mass about that joint. Although the upper arm has reduced muscle mass compared to the thigh the PLM of the elbow may have elicited a greater sympathetic response resulting in a similar cardiovascular response compared to passive knee movement.