title: Characterizing rapid-onset vasodilation to single muscle contractions in the human leg.
abstract: Rapid-onset vasodilation (ROV) following single muscle contractions has been examined in the forearm of humans, but has not yet been characterized in the leg. Given known vascular differences between the arm and leg, we sought to characterize ROV following single muscle contractions in the leg. Sixteen healthy men performed random ordered single contractions at 5, 10, 20, 40, and 60% of their maximum voluntary contraction (MVC) using isometric knee extension made with the leg above and below heart level, and these were compared with single isometric contractions of the forearm (handgrip). Single thigh cuff compressions (300 mmHg) were utilized to estimate the mechanical contribution to leg ROV. Continuous blood flow was determined by duplex-Doppler ultrasound and blood pressure via finger photoplethysmography (Finometer). Single isometric knee extensor contractions produced intensity-dependent increases in peak leg vascular conductance that were significantly greater than the forearm in both the above- and below-heart level positions (e.g., above heart level: leg 20% MVC, +138 ± 28% vs. arm 20% MVC, +89 ± 17%; P < 0.05). Thigh cuff compressions also produced a significant hyperemic response, but these were brief and smaller in magnitude compared with single isometric contractions in the leg. Collectively, these data demonstrate the presence of a rapid and robust vasodilation to single muscle contractions in the leg that is largely independent of mechanical factors, thus establishing the leg as a viable model to study ROV in humans.
authors.affiliation: Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri;
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Credeur
authors.affiliation: Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri;
authors.forename: Seth W
authors.initials: SW
authors.lastname: Holwerda
authors.affiliation: Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri;
authors.forename: Robert M
authors.initials: RM
authors.lastname: Restaino
authors.affiliation: Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri;
authors.forename: Phillip M
authors.initials: PM
authors.lastname: King
authors.affiliation: Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri;
authors.forename: Kiera L
authors.initials: KL
authors.lastname: Crutcher
authors.affiliation: Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri; Department of Biomedical Sciences, University of Missouri, Columbia, Missouri; Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri;
authors.forename: M Harold
authors.initials: MH
authors.lastname: Laughlin
authors.affiliation: Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri; Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, Missouri; and Department of Child Health, University of Missouri, Columbia, Missouri.
authors.forename: Jaume
authors.initials: J
authors.lastname: Padilla
authors.affiliation: Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri; Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri; fadelp@health.missouri.edu.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Fadel
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D005542:Forearm / Q000502:physiology; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology; D007537:Isometric Contraction / Q000502:physiology*; D007717:Knee / Q000502:physiology; D007866:Leg / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D013848:Thigh / Q000502:physiology; D014664:Vasodilation / Q000502:physiology*
keywords: blood flow; exercise onset; hyperemia; vascular conductance