TEMPORAL INHOMOGENEITY IN BRACHIAL-ARTERY BLOOD-FLOW DURING FOREARM EXERCISE

The purpose of this study was to measure the influences of muscle cont raction and exercise intensity on brachial artery blood flow during in cremental forearm wrist flexion exercise to fatigue. Twelve subjects p erformed incremental forearm exercise (increments of 0.1 W every 5 min ) with their nondominant arms. Doppler waveforms and two-dimensional i mages of the brachial artery were recorded during the last 2 min of ea ch stage. Exercise intensities were expressed as a percent of the maxi mal workload achieved (%WLmax). Blood flow was calculated during each of the concentric (CP), eccentric (EP), and recovery phases (RP) of th e contraction cycle. Blood flow during the CP of the contraction did n ot increase above resting values (25.0 +/- 10.5 mL.min(-1)) at any int ensity (100%WLmax = 21.6 +/- 6.5 mL.min(-1)). Conversely, blood flow d uring the EP and RP increased from 25.6 +/- 3.0 to 169.1 +/- 12.8 (P < 0.05), and from 24.7 +/- 3.1 to 137.9 +/- 19.5 mL.min(-1) (P < 0.05), respectively from rest to maximal exercise. Time averaged blood flow increased linearly from rest to maximal exercise (75.3 +/- 26.3 to 334 .6 +/- 141.6 mL.min(-1), P < 0.05). Thus, a significant impairment in blood flow occurs with concentric contractions during forearm dynamic exercise. The implications of a temporal disparity in blood flow to ox ygen delivery and skeletal muscle metabolism during exercise are discu ssed.