Effects of Isolated Muscle Training on Vasomotor Response and Peripheral Blood Flow

The vasomotor response, a marker of cardiovascular health, refers to the adaptability of the inner lining of blood vessels to maintain the homeostasis of vascular tone. The two main control systems that underpin this response are: the systemic autonomic control, with the sympathetic branch mediated vasoconstriction, and the endothelial cells response to mechanical and chemical stimuli, that results in smooth muscles cell vasodilation. During exercise the peripheral circulation is mostly mediated by local control, and the peripheral blood flow (BF) increases in all body districts directly involved and not involved by physical exercise. The vasodilation response depends on the magnitude of the stimulus received. To date, vascular adaptations in the brachial artery not involved in an isolated leg muscle training, is still unclear/unknown. Repetitive changes in BF occurring during exercise training may act as vascular training for vessels supplying the active muscle bed and ones distal to the active muscle. Therefore, the study aim was to evaluate the effects of isolated quadriceps muscle training (IQT) on vasomotor response in the lower limb directly involved with exercise (femoral artery) and on the upper limb, not involved with IQT (brachial artery). Ten healthy participants (4 M and 6 F; 233 yrs) underwent eight weeks of IQT (3days/week; ̴ 40min; 50 - 90% WRM) at different intensities. Maximum work rate (MWR) was assessed before, during (every 2 weeks, to redefine the training work-load) and after IQT. Pre- and post-IQT measurements of vascular function and peripheral BF were performed by flow mediated dilatation (%FMD) in the brachial artery (non-trained limb), and by passive limb movement in femoral artery (trained limb). After 8 weeks of IQT, MWR and BF in femoral artery increased significantly by 43% and 153%, respectively. No difference in %FMD was found despite 21% increase in brachial artery blood flow during exercise was found. Eight weeks of IQT improved peripheral vasomotor response only in the lower limb directly involved in IQT without affecting vascular functionality in the uninvolved upper limb, suggesting that IQT did not provide a sufficient stimulus to induce adaptations also in other districts’ vasculature.