They have literally been putting out rowing machines or other arm related machines for years.  There’s one at my gym that allows you to cycle with your arms instead of your legs, which makes more sense for those that use it, because they are generally in wheelchairs, but they still of course prefer to stay in shape, which is awesome especially considering half of those with functioning legs are not that dedicated, especially if we lost the use of our legs.

Now rowing machines generally require that you also use your legs to push out.  But if you were to lock the seat in place, you could change it.  Now the logic behind it is partly that if you see the rowers in competitions who do it quite regularly, they are in excellent shape, having both little fat and greater muscle mass and strength.  So if you use this, you too could have this effect, if of course you do it right.  It was more of a fad earlier on, but it has been used lately too. 

It gives you actually a pretty descent cardiovascular workout, depending partly on the resistance and how fast you go at the same time.  I’m a wimp, so I like lower resistance.  But it also allows me to go faster when I should use greater resistance and go slower.  But I like the faster pace that gets my heart rate up to some degree.  But some would actually tell you that it’s better than running or biking, who knew.