Zero Impact Conditioning

Hello to all you on the board!
i have a question to any of the strenght and conditioning coaches out there: is there any method of conditioning of zero impact in the legs?
explaining,a woman ex-weightlifter,asked me if there is any activity she can do to reduce body fat,but with minimun if any impact,since she cannot stand impacts after she had an accident while squating and broke the two femurs (ouch!)
Thanx in advance for any imput!

Ergometer rowing.

This obviously isn’t a muscle builder, but it’s a great replacement for running.

Of course, if even the impact of the erg is too great, swimming is obviously always an option.