title: Muscle acidosis during static exercise is associated with calf vasoconstriction.
abstract: In this study we measured (n = 6) the phosphocreatine-to-inorganic phosphate ratio (PCr/Pi), Pi, and pH with 31P-nuclear magnetic resonance (31P-NMR) in the human forearm during static work at 30% of maximal voluntary contraction (MVC) for 2 min followed immediately by 3 min of circulatory arrest (forearm arterial occlusion). Static exercise, with its central volitional and skeletal muscle metabolic and mechanical afferent components, caused a rise in heart rate (HR, 32%), blood pressure (BP, 29%), and calf vascular resistance (calf R, 30%). During forearm occlusion after static exercise, HR returned to base line, the increase in BP was attenuated by 30%, and calf R remained elevated and unchanged. The percent change in calf R was correlated with forearm cellular pH (R = 0.56, P less than 0.001) but only weakly associated with PCr/Pi (R = 0.33, P less than 0.042). 30% MVC for 1 min followed by arterial occlusion (3 min) reduced PCr/Pi by 65% and pH by 0.16 U (P less than 0.05). Calf R was unchanged. Circulatory arrest alone (20 min) caused no change in either pH or calf R but large changes in PCr/Pi (50% reduction). We conclude that 1) there is an association between forearm cellular acidosis and calf vasconstriction during static forearm exercise and 2) large changes in PCr/Pi without concomitant changes in pH are not associated with changes in calf R.
authors.affiliation: Department of Medicine and Radiology, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033.
authors.forename: L
authors.initials: L
authors.lastname: Sinoway
authors.forename: S
authors.initials: S
authors.lastname: Prophet
authors.forename: I
authors.initials: I
authors.lastname: Gorman
authors.forename: T
authors.initials: T
authors.lastname: Mosher
authors.forename: J
authors.initials: J
authors.lastname: Shenberger
authors.forename: M
authors.initials: M
authors.lastname: Dolecki
authors.forename: R
authors.initials: R
authors.lastname: Briggs
authors.forename: R
authors.initials: R
authors.lastname: Zelis
mesh_terms: D000138:Acidosis / Q000209:etiology*; D000328:Adult; D001158:Arteries; D015444:Exercise; D005542:Forearm / Q000098:blood supply; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007866:Leg; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009119:Muscle Contraction; D009132:Muscles / Q000098:blood supply*; D009135:Muscular Diseases / Q000209:etiology*; D010758:Phosphorus; D014655:Vascular Resistance; D014661:Vasoconstriction
chemical_list: D010758:Phosphorus