title: Arterial H+ regulation during exercise in humans.
abstract: Resting arterial H+ concentration ([H+]a) is in the nanomolar range (40±2 nm/L) while its production is in the millimolar range/min, with little variation from subject to subject. To determine the precision with which [H(+)]a is regulated during exercise, [H+]a, PaCO2 and ventilation (V˙(E)) were measured during progressively increasing work rate exercise in 16 normal subjects. (V˙(E)) increased with [H+]a, the latter attributable to PaCO2 increase below the lactic acidosis threshold (LAT) (ΔV˙(E)/Δ[H+]a ≈ 15   L   min(-1)   nanomol(-1)). [H+]a and PaCO2 increased, simultaneously, as work rate was increased below LAT. PaCO2 reversed direction of change between LAT and ventilatory compensation point (VCP). Above LAT, [H+]a increase relative to (V˙(E)) increase was greater than below LAT. PaCO2 decreased above the LAT, while [H+]a continued to increase. Thus the exercise acidosis was converted from respiratory, below, to a metabolic, above the LAT. We conclude that [H+]a is increased and regulated over the full range of exercise, but with less sensitivity above the LAT.
authors.affiliation: Department of Medicine, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA 90502, USA. kwasserman@LABiomed.org
authors.forename: Karlman
authors.initials: K
authors.lastname: Wasserman
authors.forename: William L
authors.initials: WL
authors.lastname: Beaver
authors.forename: Xing-Guo
authors.initials: XG
authors.lastname: Sun
authors.forename: William W
authors.initials: WW
authors.lastname: Stringer
mesh_terms: D000140:Acidosis, Lactic / Q000097:blood* / Q000175:diagnosis; D000293:Adolescent; D001158:Arteries / Q000378:metabolism* / Q000502:physiology; D001784:Blood Gas Analysis / Q000379:methods; D015444:Exercise / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D012123:Pulmonary Ventilation / Q000502:physiology; D055815:Young Adult