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Am J Physiol Heart Circ Physiol 284: H979-H986, 2003. First published November 21, 2002; doi:10.1152/ajpheart.00714.2002
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Vol. 284, Issue 3, H979-H986, March 2003

Skeletal muscle blood flow and flow heterogeneity during dynamic and isometric exercise in humans

Marko S. Laaksonen1, Kari K. Kalliokoski1, Heikki Kyröläinen3, Jukka Kemppainen1, Mika Teräs1, Hannu Sipilä1, Pirjo Nuutila1,2, and Juhani Knuuti1

1 Turku Positron Emission Tomography Centre and 2 Department of Medicine, University of Turku, FIN-20521 Turku; and 3 Neuromuscular Research Centre, University of Jyväskylä, FIN-40351 Jyväskylä, Finland

The effects of dynamic and intermittent isometric knee extension exercises on skeletal muscle blood flow and flow heterogeneity were studied in seven healthy endurance-trained men. Regional muscle blood flow was measured using positron emission tomography (PET) and an [15O]H2O tracer, and electromyographic (EMG) activity was recorded in the quadriceps femoris (QF) muscle during submaximal intermittent isometric and dynamic exercises. QF blood flow was 61% (P = 0.002) higher during dynamic exercise. Interestingly, flow heterogeneity was 13% (P = 0.024) lower during dynamic compared with intermittent isometric exercise. EMG activity was significantly higher (P < 0.001) during dynamic exercise, and the change in EMG activity from isometric to dynamic exercise was tightly related to the change in blood flow in the vastus lateralis muscle (r = 0.98, P < 0.001) but not in the rectus femoris muscle (r = -0.09, P = 0.942). In conclusion, dynamic exercise causes higher and less heterogeneous blood flow than intermittent isometric exercise at the same exercise intensity. These responses are, at least partly, related to the increased EMG activity.

electromyography; positron emission tomography




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