Blood flow during muscle contraction and relaxation in rhythmic exercise at different intensities

Effect of contraction force on blood flow during the contraction and relaxation phase of rhythmic handgrip exercise was studied on 6 healthy women. Velocity of blood flow in the brachial artery and the diameter of the artery were studied by Doppler-ultrasound method. Both the peak and mean velocity of the blood flow were significantly higher during the relaxation period than during contraction, and the velocity during the relaxation period was significantly higher in 30% MVC exercise than in 10% MVC exercise. However, no significant differences were found in the diameter of the artery between resting and exercise conditions, nor between exercises at different intensities. Thus blood flow during the relaxation phase was significantly increased from 135.7 +/- 18.2 ml.min-1 (10% MVC) to 182.5 +/- 19.6 ml.min-1 (30% MVC) by an increased contraction force, whereas blood flow during the contraction phase was hardly affected by increased contraction force.