I just ran across an old quote of mine that Reflexology Association of Canada liked.
"Kevin Kunz, one of the pioneers of reflexology, puts it best -- 'Imagine stepping on a tack. Your whole body reacts because of something perceived by the foot. Reflexology with a full range of pressure sensors, utilizes the same body system of fight or flight to relax the body.' Indeed,the feet and hands are more sensitive than most people realize. Similar to how we use our eyes to detect light, the hands and feet detect pressure, stretch, movement and weight distribution."
As we age our feet and hands lose communication with our brains. So stimulating the feet and hands as a sensory organs with different signals like pressure, stretch and movement can reconnect that trunk line between our extremities and our brain.
Even heat/cold, vibration and the scratchy surface of a loofah sponge or hairbrush can reestablish those lost connections. So when you think of the whole body reacting to stepping on a tack that same communication system can keep all our body parts connected to each other.
So you don't have to step on a tack to get the same effect.