Editorial Effects of Vascular Occlusion on Surface Electromyography and Muscle Oxygenation During Isometric Contraction

Objective: To investigate changes in motor-unit activity and muscle oxygenation (MO) during isometric contraction with and without vascular occlusion using surface electromyography (EMG) and near-infrared spectroscopy. Design and Setting: MO and EMG of the right vastus medialis muscle were measured during isometric contraction at 30%, 50%, and 70% maximal voluntary contraction (MVC), with and without vascular occlusion. Participants: 6 healthy men. Results: Integrated EMG (IEMG) and mean power frequency were significantly higher with vascular occlusion at 30% and 50% MVC. MO reduction at each load was significantly lower with vascular occlusion. A significant positive correlation was found between IEMG and changes in MO level under both conditions. Conclusions: These results suggest that oxygen supply to active muscles was impaired by occlusion and that type II fibers were then preferentially recruited, which suggests that hypertrophy occurs in low-intensity exercise in patients with limitations resulting from advanced age, pain, or postsurgery limitation.