No need to worry about the fabric or cord getting dirty or sweaty, they are machine washable on your lowest heat cycle. Preferably 30° or lower. Just place them inside a sock!
Aluminium is a lightweight metal that will not tarnish or rust. But that doesn't mean aluminium doesn't require any care to stay shiny and bright. Take off your bracelet while cleaning or doing any tasks that involve chemicals.
Be aware that darkened stamped areas can fade in time if your jewellery is worn while swimming, showering, washing dishes etc, like most jewellery, it tends to not like water. Being mindful will help their longevity.