title: Skeletal muscle blood flow and flow heterogeneity during dynamic and isometric exercise in humans.
abstract: 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 [(15)O]H(2)O 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.
authors.affiliation: Turku Positron Emission Tomography Centre, University of Turku, FIN-20521 Turku, Finland. marko.laaksonen@tyks.fi
authors.forename: Marko S
authors.initials: MS
authors.lastname: Laaksonen
authors.forename: Kari K
authors.initials: KK
authors.lastname: Kalliokoski
authors.forename: Heikki
authors.initials: H
authors.lastname: Kyröläinen
authors.forename: Jukka
authors.initials: J
authors.lastname: Kemppainen
authors.forename: Mika
authors.initials: M
authors.lastname: Teräs
authors.forename: Hannu
authors.initials: H
authors.lastname: Sipilä
authors.forename: Pirjo
authors.initials: P
authors.lastname: Nuutila
authors.forename: Juhani
authors.initials: J
authors.lastname: Knuuti
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000000981:diagnostic imaging / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D012016:Reference Values; D012039:Regional Blood Flow / Q000502:physiology; D013314:Stress, Mechanical; D014055:Tomography, Emission-Computed