Skeletal Muscle Blood Flow in the Brachial Artery and its Regulation During Increasing Intensities
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The aim of this study was to identify the blood flow pattern during a handgrip exercise test, and hence when blood flow results in the highest shear rate on the vessel walls. It was hypothesized that shear rate increased linearly with increased workload in forearm muscle work and up to 80% of maximal work and that it plateaued from there onwards. It was also hypothesized that peak measurements of shear rate and blood velocity would provide more valid results compared to average measurements of the same parameters. Peak and average shear rate, blood velocity and diameter was measured with ultrasound Doppler in the brachial artery of the non-dominant arm during incremental handgrip exercise to exhaustion in 21 healthy sedentary men. Peak shear rate and blood velocity was found to increase significantly (p<0.05) up to 80% of maximal effort, and plateau from there onwards. Peak diameter, average shear rate and average blood velocity was not found to increase significantly. It was concluded that the plateau in shear rate and blood velocity at 80% of maximal effort might be a consequence of a limitation in the forearm muscles ability to accept the amount of blood flow needed to maintain peak exercise intensities.