oxygen, what we call venous blood, is pumped
 
 through the leg muscle pump from the legs to the
 
 heart.
 
 "The veins of the legs have valves which are
 
 similar to those of the heart. They allow blood to pass
 
 through towards the heart while they prevent the
 
 blood flowing backwards towards the foot. In this way
 
 they only allow blood flow in one direction: toward
 
 the heart.
 
 "During the pumping phase or muscle
 
 contraction, the pressure within the veins is increased,
 
 pumping the venous blood towards the heart. "During the filling phase or muscle relaxation,
 
 the pressure within the veins is reduced and the veins
 
 fill themselves with blood in preparation for the next
 
 pumping phase. This prevents thrombosis, blood
 
 clotting, and increases peripheral circulation which is
 
 necessary for tissue nutrition, oxygenation and
 
 removal of metabolic waste. And yes, muscle
 
 strength, prevention of atrophy.
 
 "Well?" he said standing back with his hands
 
 on his hips.
 
 "Well what?"
 
 "Aren't you impressed yet?"
 
 "Overwhelmed," I said and he laughed. "Okay. Let's just start and see where we go,
 
 okay?"
 
 He went over to the equipment and brought out
 
 a rolled thick mat that he undid and spread on the
 
 floor. Then he looked at me.
 
 "We'll go through a very basic evaluation. You
 
 know what I want you to do first?"