Lifting 5lb weights -- unless you're starting out not strong at all -- won't do much to increase strength. You know how, say, a crane can lift a 20,000-pound rock 10,000 times before it breaks, but lifting a 20-pound rock doesn't stress the crane one thousandth as much? Your muscles work the same way: lifting a 5-pound weight is not going to make you stronger at all. If you want to get stronger, you need to lift something your body thinks is heavy.