Actually, there are many machines which would be helpful to an amputee - in fact, they would represent that person's only option, in many instances. Someone with only one arm could never use a barbell ... but there are certain exercises they could perform with a dumb-bell.
It's a question of balance. This is where some of the exercise machines would benefit them. For example, any pressing machine - say, bench press or shoulder press - on which the two sides are joined and cannot move independantly and upon which the person can sit (yielding three points of contact/support) would be practical. When I was a trainer, I often had people use such machines to strengthen a 'weak side' - they would simply 'ease off' the strong side, a little.
With dumb-bells, basically, the closer 'bell stays to the body's centre line, the easier the exercise would be for an amputee. For example, pressing directly overhead, while seated on a bench, would be easy enough - doing a lateral raise, in which the 'bell is swung out to the side, to shoulder height, would be far more difficult, if not impossible. This exercise could be performed, though, using a low pulley.
There are so many options for even an amputee - far too many to present here. If you have any more specific questions (like what exercises for a particular bodypart, etc.), feel free to drop me a line.
(Hmm ... just give me time to change my options, here, so that I can be contacted. I just registered, today. *grin*)
Cheers -
Al
