Everyone produces some alpha activity prior to falling asleep. Difficulty producing alpha activity is associated with sleep onset insomnia. First, relaxed people are very still. If they move at all, they do so slowly and gently. Second, muscle tone is greatly diminished when people relax.
Muscle tone is the background level of muscle tightness in between overt muscle movements.
Many of us get sore, aching muscles in our lower backs and shoulders or develop muscle tension headaches when muscle tone is too high for too long. The third system that changes with relaxation is the autonomic nervous system. This is the part of the nervous system outside of our brain and spinal cord that controls digestion, blood circulation, and other our basic biological processes. This nervous system controls parts of our body that we do not normally have to attend to, like when our heart beats or the level of activity of our gastrointestinal system. This autonomic nervous system has two branches, the sympathetic nervous system and the parasympathetic nervous system.