Endless-path Machines
You may not have heard of this term but if you have been to a gym then you most certainly would instantly recognise one of these machines. An endless-path machine is designed to give you workout that can continue on as long as the person wants i.e. not limited by distance. They are really based around an aerobic workout and probably the most common ones that everyone will know are the running machine and the cycling machine (http://en.wikipedia.org/wiki/Exercise_bicycle).
These machines stay in one place but can chart the distance that you have covered as if you were running or cycling outside. They can be adjusted to difficulty levels, for example the running machine can increase its speed as well as the gradient that the person is running along.
These machines give a whole body workout and are great for the heart, lungs and blood flow around the body. Some other endless-path machines available on the market include rowing machines, elliptical machines, stair machines, ski machines and many more.