(英) Oxygen supply system at contracting muscle may be controlled by the anatomical features such as vasoconstriction or vasodilation as well as muscle functional and anatomical features. Using both near infrared spectroscopy (NIRS) and a B-mode ultrasound imaging (USI) devices, we tried to identify the characteristic features of muscle oxygen status and arterial diameter response during muscle contraction. Ten healthy subjects performed the sustained isometric handgrip of 30% maximal voluntary contraction for 1 min. The NIRS and USI devices were positioned around the flexor carpi ulnaris muscle. The total-Hb (sum of oxygenated and deoxygenated Hb signal) and the diameter of ulnaris artery were measured during trial. The total-Hb (optical density) decreased (0.0 to 0.12±0.04) during the contraction and then increased (to 0.15±0.05) over the resting level during the recovery. The vessel diameter, however, decreased (3.3±0.5 to 2.6±0.5mm) and recovered (to 3.4±0.5mm) after the contraction. These results suggest that the sustained muscle contraction produced the larger vasocontraction and decrement of total-Hb due to the larger intramuscular pressure. (日)