satcong, sounds like a good investment. $250 is a lot cheaper than what most of us spend on equipment. [:)] My car quit running in September, and it isn't worth fixing. I'm walking when I can't find a ride. Also, my chainsaw quit, and I use mostly wood to heat my house in the winter. Between those two things, I'm on my way to losing my love handles.
Back to the topic: according to a doctor I talked to while my wife was having a machine work on her calf muscles after breaking her heel, he said that if it is powered by a battery, it simply can't be strong enough to work the muscle enough to build it up. The machine seemed to help my wife for a short while. She hadn't put weight on her right leg for just over six months, and her calf was about the size of her wrist! Twice a week with the machine really helped, again, for a short while. It got her back up to about (wild-guess) 30% strength, but then it didn't seem to help any past that point.z