A steady, firm pressure from both should keep the arm about even. Now, the one being tested should simply think of something hateful or disgusting. The same pressure should then be applied to the wrist. If all is right with this person, their arm will fall as if someone were standing on it. This is because the test is not truly of the muscle itself but of the frequency of the energy to work the muscle.
Negative thoughts create energy short-circuits which weaken the body and the mind.
One more thing, the one being tested should now think of someone or something loved. The arm should now be strong and solid. There are several excellent therapies currently in use such as Acupuncture and Touch for Health, used by Chiropractors, which depend on these meridians. This research suggests that the whole energy system is much more complex than originally understood by the Chinese. As with anything new, the first possibility is something magical or otherworldly.