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.
6 healthy men.
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.
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.
Yamada and Tanaka are with the Dept of Rehabilitation; Kusaka, the Maternal and Perinatal Center; Mori and Norimatsu, the Dept of Orthopedic Surgery; and Itoh, the Dept of Pediatrics, Faculty of Medicine, Kagawa University, Kagawa, Japan 761-0793.