The purpose of this dissertation was to examine the effect of eccentric exercise-induced muscle injury on local vascular function and muscle blood flow in humans. Healthy, male subjects performed maximal eccentric contractions to induce muscle injury to the forearm flexor muscles, with subsequent changes in maximal isometric strength and vascular responses assessed at one, 24, 48, and 96 hours post-injury. Endothelial-dependent and-independent vasodilation was measured using brachial artery flow-mediated dilation (FMD) and sublingual nitroglycerin administration, respectively. Mean blood velocities were measured by Doppler ultrasound and later used for the calculation of blood flow and the shear stress area under the curve (SSAUC). Subjects performed sub-maximal handgrip exercise 48 hours following injury and muscle blood flow was assessed via Doppler ultrasound.
Eccentric exercise resulted in significant decreases in maximal isometric strength for up to 96 hours. Endothelial-dependent and –independent vasodilation was also significantly impaired for up to 96 hours following eccentric-induced injury. The shear stress stimulus (SSAUC) responsible for the FMD response was significantly reduced from one to 48 hours post-injury. However, resting blood pressure and blood flow remained the same throughout the duration of the study despite an increase in brachial artery diameter at one and 48 hours following eccentric exercise. Additionally, the muscle blood flow response to dynamic sub-maximal handgrip exercise was not significantly different 48 hours post-injury.
In summary, these results suggest that skeletal muscle injury results in prolonged impairment of local vascular function without influencing subsequent muscle blood flow at rest or during sub-maximal exercise.