title: Glycogen depletion-induced lactate reductions attenuate reflex responses in exercising humans.
abstract: Post leg exercise circulatory arrest (PLE-CA) raises blood pressure (BP) and reduces peak forearm vascular conductance (C). This reflex is evoked by activation of muscle afferents that are often sensitive to lactic acid. We tested the hypothesis that lactic acid reductions induced by muscle glycogen depletion would attenuate the lower-limb metaboreceptor-mediated pressor and forearm vasoconstrictor responses. Eleven subjects had C measured (plethysmography) during post leg exercise circulatory arrest (PLE-CA) (supine bicycle exercise for 9 min, 10 s at 75% VO2max before and after undergoing a glycogen-depletion paradigm (24-h fast followed by 10 min of supine leg exercise at 75% VO2max). In six subjects with lower lactate values, C during PLE-CA was higher after glycogen depletion (0.39 +/- 0.05 vs. 0.21 +/- 0.01 ml.min-1.100 ml-1 x mmHg-1; P < 0.01) and BP was lower (113 +/- 6 vs. 128 +/- 6 mmHg, P < 0.01). In five subjects without attenuated lactate responses, C and BP during PLE-CA were not different. Muscle biopsies (n = 5) demonstrated that the paradigm lowered muscle glycogen concentrations. Thus glycogen depletion-induced reductions in muscle lactate are associated with reduced muscle metaboreceptor-mediated responses.
authors.affiliation: Division of Cardiology, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033.
authors.forename: L I
authors.initials: LI
authors.lastname: Sinoway
authors.forename: K J
authors.initials: KJ
authors.lastname: Wroblewski
authors.forename: S A
authors.initials: SA
authors.lastname: Prophet
authors.forename: S M
authors.initials: SM
authors.lastname: Ettinger
authors.forename: K S
authors.initials: KS
authors.lastname: Gray
authors.forename: S K
authors.initials: SK
authors.lastname: Whisler
authors.forename: G
authors.initials: G
authors.lastname: Miller
authors.forename: R L
authors.initials: RL
authors.lastname: Moore
mesh_terms: D000328:Adult; D001706:Biopsy; D001794:Blood Pressure; D005542:Forearm / Q000098:blood supply; D006003:Glycogen / Q000172:deficiency*; D006339:Heart Rate; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology; D007773:Lactates / Q000378:metabolism*; D019344:Lactic Acid; D009132:Muscles / Q000473:pathology; D005082:Physical Exertion; D012018:Reflex / Q000502:physiology*; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D012867:Skin / Q000098:blood supply
chemical_list: D007773:Lactates; D019344:Lactic Acid; D006003:Glycogen