We have to remember what makes a muscle change tone. That would be the CNS ( central nervous system). Understanding the Nerves that innervate the muscle  where they form and the direction they travel helps us to understand how with just the simplest or softest touch can make a change. This is why we teach this to both Reflexology Students and Massage  students here at School of Holistic Massage and Reflexology this as well. Something to think about on the feet  there are over 8000 yes over 8000 nerve endings on  just the surface of the plantar side of the foot.