B-29 Free Communication/Poster - Concussion

Abstract

Hyperoxia can cause substantial reductions in the peripheral and coronary blood flow at rest and during exercise. This has been attributed to an increase in reactive oxygen species (ROS) generation during hyperoxia. Indeed, vitamin C has been shown to restore coronary flow during administration of 100% O2. However, this model has not been studied in local exercising skeletal muscle. PURPOSE: The primary aim of this study was to investigate the role of ROS in hyperoxia induced reductions in skeletal muscle blood flow during forearm exercise. METHODS: 12 young healthy adults (28±2 years) performed forearm handgrip exercise under normoxia and hyperoxia with saline or Vitamin C infusions. Forearm blood flow (FBF) was measured using Doppler ultrasound while forearm vascular conductance (FVC) was calculated from FBF and mean arterial pressure (brachial artery catheter). RESULTS: Under the control (saline) condition, the percent change of FBF and FVC during hyperoxic exercise (86.3±5.1% and 86.8±5.2%, respectively) was reduced as compared to normoxia (mean=100%) (P 20%, 10-20%, and 20%), infusion of Vitamin C substantially increased the FBF and FVC responses to hyperoxic exercise (102.0±5.2% and 100.8±6.1% respectively) compared to control (saline) conditions (67.1±4.0% and 66.8±3.6% respectively) (P<0.05). However, this was not observed with individuals in the other 2 sub-groups. CONCLUSIONS: Our data suggests that in participants with the greatest hyperoxia induced vasoconstriction during forearm exercise, ROS generation may be a contributing factor. Hence, when Vitamin C is administered during hyperoxic exercise, the FBF seems to be restored only in the individuals who have a 20% or greater decrease in FBF.