Abstract 18596: Regional Assessment of Lower Extremity Tissue Oxygenation in Athletes Using Blood Oxygen Level-Dependent Magnetic Resonance Imaging

Abstract

Background: Blood oxygen level-dependent (BOLD) MRI allows for evaluation of hemoglobin oxygenation within skeletal muscle, providing a non-invasive index of microvascular function. This study evaluated differences in relative signal intensity of BOLD MRI among lower extremity muscle groups during transient ischemia and reactive hyperemia in college football athletes, while also comparing strength and functional exercise results. Methods: BOLD MRI was performed on the lower leg of 19 males (19.8 ± 1.0 yrs) with a 3T magnet to evaluate regional changes in signal intensity among individual muscle groups during ischemia and reactive hyperemia induced by proximal cuff occlusion. Athletes were separated by position (larger linemen vs. smaller position players) for comparison purposes. The peak hyperemic value (PHV), or the maximum percent change in BOLD signal intensity from baseline, was assessed for each muscle group. Athletes’ lower body strength and jumping ability were evaluated and compared to BOLD responses. Results: Linemen presented with higher body fat and systolic blood pressure (p<0.05). Athletes did not differ in maximal lower body strength; however, position players had greater vertical and broad jump performance (p<0.0001). In analysis of all athletes, the soleus muscle, a slow twitch muscle generally with high capillary density, exhibited the largest PHV. The PHVs of gastrocnemius muscles for position players were significantly higher than linemen (p=0.03) and were associated with greater jumping performance. No differences were observed in other muscle groups when comparing position players and linemen. Conclusions: BOLD MRI offers a non-invasive technique for quantifying regional differences in lower extremity tissue oxygenation in the evaluation of microvascular function in relation to functional performance. Evaluation of changes in BOLD responses may help to evaluate and optimize exercise training for improved function.