In this study, the influence of acupuncture at SP3 on the quadriceps femoris muscle during extension movement of the knee joint using the meridian concept was investigated in patients with musculoskeletal diseases. Sixty healthy individuals (mean age, 23.7 years) provided their informed consent to participation during extension movement of the knee joint. The subjects received different types of acupuncture stimulation at SP3: (1) the retaining needle method, (2) the single needle method, and (3) no stimulation. The subjects performed isometric contraction with 40% of the maximum voluntary contraction and 60° knee flexion while receiving the different acupuncture stimulations. Surface electromyography (EMG) of the vastus medialis obliquus, vastus medialis longus, rectus femoris, and four sites within the vastus lateralis was performed before, during, and 15 min after the start of the acupuncture stimulations during extension movement of the knee joint. The relative integrated EMG (IEMG) recorded during and 15 min after acupuncture stimulation was compared with the value recorded before acupuncture which was used as the reference value. The Tukey method was used for statistical analyses (significance, p<0.05). The relative IEMG of the vastus medialis obliquus after 15 min of the retaining needle method was significantly more than that observed without stimulation. After 15 min of the retaining needle method, the relative IEMG of the vastus medialis obliquus exhibited suppressed muscle function.
