Using just a needle to relax a muscle is as simple as putting it in the belly of the muscle. That triggers a electro-chemical reaction that causes structured water to form around the needle and in surrounding tissue. that causes the sarcomere to lengthen, thus relaxing the muscle. This process is driven by infrared energy (heat) which is represent in the body. This process takes 5-15 minutes to reach equilibrium. Electro-acupuncture can override this effect depending on the frequency used.Using a low frequency (below 40 Hz) will tonify the muscle and increase muscle tone. But you cannot use too strong a stimulus and cause a sympathetic (stress) reaction. And using microcurrent is better. To Relax a muscle with electro-acupuncture, you need to use a frequency above about 80 Hz. I typically use 100 Hz to release endorphins as well. Of course, there are certain points that are associated with certain muscle groups and needling them usually will relax them if that is what is needed. Using just a needle and getting Qi on these points will usually relax the muscle. Whereas, on motor points, just needling them will cause the muscke to relax. You need electrical stimulation at the right range of frequencies to tonify and improve muscle tone.