Immediate exercise hyperemia in humans is contraction intensity dependent: evidence for rapid vasodilation

• Published in: Journal of applied physiology (1985) Vol. 96; no. 2; pp. 639 - 644
• Main Authors: Tschakovsky, M. E, Rogers, A. M, Pyke, K. E, Saunders, N. R, Glenn, N, Lee, S. J, Weissgerber, T, Dwyer, E. M
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.02.2004; American Physiological Society
• Subjects: Adult; Arms; Biological and medical sciences; Blood Pressure - physiology; Blood vessels; Exercise; Exercise - physiology; Female; Forearm - blood supply; Forearm - physiology; Fundamental and applied biological sciences. Psychology; Heart Rate - physiology; Humans; Hyperemia - physiopathology; Male; Muscle Contraction - physiology; Muscle, Skeletal - blood supply; Muscle, Skeletal - physiology; Vasodilation - physiology; Veins - physiology; Physical exercise; Human; muscle pump; Intensity; Striated muscle; Muscle contraction; Vasodilation; Blood flow; Vasomotricity; Vertebrata; Mammalia; muscle blood flow; Hemodynamics
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00769.2003

School of Physical and Health Education,and Department of Physiology, Human Vascular Control Laboratory, Queen's University, Kingston, Ontario, Canada K7L 3N6 Submitted 24 July 2003 ; accepted in final form 13 October 2003 We tested the hypothesis that rapid vasodilation proportional to contraction intensity contributes to the immediate (first cardiac cycle after initial contraction) exercise hyperemia. Ten healthy subjects performed single 1-s isometric forearm contractions at 5, 10, 15, 20, 30, 50, and 70% maximal voluntary contraction intensity (MVC) in arm above heart (AH) and below heart (BH) positions. Forearm blood flow (FBF; brachial artery mean blood velocity, Doppler ultrasound), mean arterial pressure (arterial tonometry), and heart rate (electrocardiogram) were measured beat by beat. Venous emptying (measured with a forearm strain gauge) was already maximized at 5% MVC, indicating that increases in contraction intensity did not further empty the forearm veins. Immediate increases in FBF were linearly proportional to contraction intensity from 5 to 70% MVC in AH (slope = 4.4 ± 0.5% FBF/%MVC). In BH, the immediate increase in FBF demonstrated a curvilinear relationship with increasing contraction intensity and was greater than AH at 15, 20, 30, and 50% MVC ( P < 0.05). Peak changes in FBF were greater in BH vs. AH from 10 to 50% MVC, even when venous refilling was complete ( P < 0.05). These data support the existence of a rapid-acting vasodilatory mechanism(s) at the onset of human forearm exercise. muscle blood flow; muscle pump Address for reprint requests and other correspondence: M. E. Tschakovsky, Human Vascular Control Laboratory, School of Physical and Health Education, Queen's Univ., Kingston, ON, Canada K7L 3N6 (E-mail: mt29{at}post.queensu.ca ).