Cardio work without using legs?

[Brahms]

There are days in my workout schedule that really hamper my running because my legs or lower back is too tired from previous workouts. Does anyone know of a way to get good cardio in without much use of the legs?

[ryuage]

these use ur legs but try a bike or swimming

[body]

swimming, with a front/back crawl kick, do not use the elgs that much.