When you look at an anatomical chart of the human body you will notice that hardly any muscles run straight up and down or across the body. Our muscles spiral around bones and joints and wind across the trunk. Natural movement occurs in spirals for that reason, and that is how I address the strengthening of muscle. When I am not using closed chain exercises, which includes weight bearing for strong bones as well as muscles, I use diagonal and spiral movement pattern against elastic bands or manual resistance, which keeps me in shape as well as you.
The only mechanical contraption I use in treatment is called the "Flight Plan". It consists of a set of padded bolsters attached to a cast iron frame to provide a stable surface for anti-gravity decompression of the spine and anti-gravity trunk strengthening. I use a mat table and large exercise balls for stretching, core strengthening, joint stabilization, balance- and coordination training. I do not use mechanical forms of repetitive motion such as exercise bicycles or stair steppers, for example. When your muscle balance and joint motion are functional enough to tolerate such machines without doing damage to the joints I can refer you on to a gym. I also refer people on to Yoga classes for maintenance and prevention.