Bone loss from micro-gravity is a serious issue, especially for a 3 year Mars trip. NASA says “The proximal femoral bone loses 1.5% of its mass per month, or roughly 10% over a six-month stay in space.” So if the astronauts do not exercise daily they will lose a percentage of over 60% of their bone density. The Astronaut would not be able to be active. Now that the scientists have more data they now use tension. There is a feature on the grips where they have rubber, which allows the astronaut to work their fingers by pressing on them. The muscles the astronauts work when the they use both handles with their hands are their back and shoulder muscles. The muscles that the astronauts use when they use one handle on the foot and the other on the hand are their biceps. The materials are corresponding with the colors. Every orange part is rubber, every gray part is aluminum, and every black part is nylon. The astronauts will have to bring glue, to stick the rubber grip in place.