Comparison of intramuscular and venous blood pH, PCO2 and PO2 during rhythmic handgrip exercise

Abstract

Oxygen and acid-base status during exercise is well established for the lungs, large arteries and veins. However, values for these parameters in exercising muscle are less frequently reported. In this study we examined the relationship between intramuscular PO2, pH, PCO2 and the comparable venous values during rhythmic isometric handgrip exercise at target levels of 15%, 30% and 45% of maximum voluntary contraction (MVC). A small fiber optic sensor was inserted into the flexor digitorum profundus (FDP) muscle for continuous measurement of intramuscular (IM) PO2, pH and PCO 2. Venous blood samples were taken from the forearm every minute during each exercise bout. IM pH and PCO2 were similar to their venous counterparts at baseline, but the difference between IM and venous values increased when exercise exceeded 30% MVC. During exercise at 15% MVC and greater, venous PO2 declined from 40 to 21 Torr (≃5.3 to 2.8 kPa). IM PO2 declined from 24 to 8 Torr with 15% MVC, and approached 0 Torr at 30% MVC and 45% MVC. IM pH declined rapidly when IM PO2 reached 10 Torr and continued to decrease with increasing exertion, despite an IM PO2 near 0 Torr. © 2007 IOP Publishing Ltd.