title: Factors influencing hydrogen ion concentration in muscle after intense exercise.
abstract: To assess the importance of factors influencing the resolution of exercise-associated acidosis, measurements of acid-base variables were made in nine healthy subjects after 30 s of maximal exercise on an isokinetic cycle ergometer. Quadriceps muscle biopsies (n = 6) were taken at rest, immediately after exercise, and at 3.5 and 9.5 min of recovery; arterial and femoral venous blood were sampled (n = 3) over the same time. Intracellular and plasma inorganic strong ions were measured by neutron activation and ion-selective electrodes, respectively; lactate concentration ([La-]) was measured enzymatically, and plasma PCO2 and pH were measured by electrodes. Immediately after exercise, intracellular [La-] increased to 47 meq/l, almost fully accounting for a reduction in intracellular strong ion difference ([SID]) from 154 to 106 meq/l. At the same time, femoral venous PCO2 increased to 100 Torr and plasma [La-] to 9.7 meq/l; however, plasma [SID] did not change because of a concomitant increase in inorganic [SID] secondary to increases in [K+], [Na+], and [Ca2+]. During recovery, muscle [La-] fell to 26 meq/l by 9.5 min; [SID] remained low (101 and 114 meq/l at 3.5 and 9.5 min, respectively) due almost equally to the elevated [La-] (30 and 26 meq/l) and reductions in [K+] (from 142 meq/l at rest to 123 and 128 meq/l). Femoral venous PCO2 rose to 106 Torr at 0.5 min postexercise and fell to resting values at 9.5 min.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, McMaster University Health Sciences Centre, Hamilton, Ontario, Canada.
authors.forename: J M
authors.initials: JM
authors.lastname: Kowalchuk
authors.forename: G J
authors.initials: GJ
authors.lastname: Heigenhauser
authors.forename: M I
authors.initials: MI
authors.lastname: Lindinger
authors.forename: J R
authors.initials: JR
authors.lastname: Sutton
authors.forename: N L
authors.initials: NL
authors.lastname: Jones
mesh_terms: D000136:Acid-Base Equilibrium; D000328:Adult; D001639:Bicarbonates / Q000378:metabolism; D001769:Blood / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000378:metabolism; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D008297:Male; D009132:Muscles / Q000378:metabolism*; D005082:Physical Exertion
chemical_list: D001639:Bicarbonates; D007773:Lactates; D002245:Carbon Dioxide; D019344:Lactic Acid