If you're talking about cleaning gym eqpt, I agree I would not use
bleach. Alcohol is OK

But would it be strong enough?
Im talking about equipment that has been sweated on and kept in a
basement when not used. In other words, a germ and mold breeding
ground.

or you could use on of the kitchen/bath cleaners
that come in anti-bacterial version. Also, lysol would work.

Might be expensive, I would use it a couple of times a week, alcohol
should be cheap.