title: Physicochemical analysis of acid-base responses to prolonged moderate exercise in late gestation.
abstract: Stewart's physicochemical approach was employed to investigate the safety of an average recreational and occupational activity (prolonged moderate exercise) on maternal acid-base homeostasis. The responses of 10 healthy, physically active pregnant women (PG, gestational age 34-38 weeks) were compared with those of 10 non-pregnant female controls (CG). Subjects cycled for 40 min at 85% of their measured ventilatory threshold (VT). During the transition from rest to exercise, hydrogen ion concentration ([H+]) increased significantly and bicarbonate concentration ([HCO3-]) decreased significantly in both groups. Total weak acid ([Atot]) increased significantly with exercise in both groups, whereas the strong ion difference ([SID]) and CO2 tension (PaCO2) did not change significantly with exercise. Values for [H+], [HCO3-], PaCO2, [Atot] and [SID] were significantly lower in the PG vs. CG under all experimental conditions. Acid-base responses to prolonged moderate exercise are quantitatively similar in the pregnant vs. non-pregnant state. However, pregnant women maintain a lower plasma [H+] (approximately 3 neq/L (1 neq/L=1 nmol/L)) throughout rest, exercise, and recovery, as a result of lower values for PaCO2 and [Atot], which is partly offset by a lower [SID]. The results indicate that prolonged moderate exercise appears to be well tolerated by healthy recreationally and occupationally active pregnant women.
authors.affiliation: School of Physical and Health Education, Queen's University, Kingston, ON K7L 3N6, Canada. scharle@uwo.ca
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Charlesworth
authors.forename: Larry A
authors.initials: LA
authors.lastname: Wolfe
authors.forename: Gregory A L
authors.initials: GA
authors.lastname: Davies
mesh_terms: D000136:Acid-Base Equilibrium / Q000502:physiology*; D000328:Adult; D001642:Bicycling / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D011247:Pregnancy; D011263:Pregnancy Trimester, Third / Q000097:blood* / Q000502:physiology*; D012964:Sodium / Q000097:blood; D013997:Time Factors
chemical_list: D002245:Carbon Dioxide; D012964:Sodium