Blood Flow and Oxygen Extraction and Rest and Maximal Exercise In Forearm Flexors

Abstract

Aerobic endurance is found to be important for health, quality of life and performance. The main factor determining ones aerobic endurance is maximal oxygen uptake (VO2max). What limits our VO2max has long been a debated subject. Some studies propose it is central factors while others propose peripheral or both. When studying peripheral aspect most studies use small active muscle mass such as legs. This will not stress the cardiac output (Q), hence oxygen  delivery can exceed its normal boundaries and there will not be any central limitations. This study investigated blood flow and oxygen extraction at rest and  maximal exercise in forearm flexor muscles in moderately trained individuals. Eight subjects participated and performed a maximal test using a handgrip dynamometer. Blood flow was measured in both brachial artery and basilica vein using Doppler ultrasound. Oxygen extraction was measured using a venous catheter inserted into the basilica vein. This is to our knowledge the first study conducted measuring blood flow and oxygen extraction at rest and during maximal exercise using this method. Blood flow increased significantly both in brachial artery and basilica vein by 80% and 63%, respectively from rest to maximal work. Oxygen extraction also increased significantly with 55% from rest to maximal work. Basilica vein represented flow from flexor forearm muscles. A pilot study using skin heating excluded draining from the skin. Thus, the method used in this study was found to be precise in detecting oxygen extraction.  This study suggests that blood flow and oxygen extraction increased from rest to maximal exercise and maximal work indicate limitations in oxygen extraction and not blood flow.