Immediate characteristics of acupuncture have been confirmed by relevant studies; however, the current study on the time effect of acupuncture in improving upper limb forearm muscle endurance is still limited. The aims of this study are to explore: (1) whether acupuncture can improve female forearm muscle endurance compared to sham acupuncture and (2) whether the changes in forearm muscle endurance after RA are time-dependent.
Thirty-six healthy female students were recruited to participate in isokinetic tests of elbow flexion/extension (Flex/Ext) from maximum flexion to maximum extension as much as possible using an isokinetic dynamometer at a speed rate of 60°/sec.
Participants in the acupuncture group were stimulated at Quchi (LI11), Shousanli (LI10), Hegu (LI4), Xiaohai (SI8), Tianjing (SJ10), and Waiguan (SJ5) acupoints for 20 min, while the sham acupuncture group needling was near at these acupoints. The values of the isokinetic parameters and surface electromyography (sEMG) signals were recorded before and after acupuncture.
After acupuncture, the isokinetic parameters values (average torque, work, power, and speed), the sEMG values at four major muscles, and the joint stiffness of elbow Flex/Ext were significantly increased (p < 0.05). The enhancement of forearm muscle endurance lasted approximately 7-21 min (from post1 to post3/post4), indicating that the effect of acupuncture to improve elbow Flex/Ext muscle endurance is time-dependent.
Therefore, this study found that acupuncture can immediately improve the forearm muscle endurance of healthy women compared with sham acupuncture, and this effect can last approximately 7-21 min until the acupuncture efficacy decreased or disappeared.