do push ups man, they work like a charm. last summer i did 500 push up 3x a week to get my school body back in shape, and i was hella turnin heads. did them for about 3 weeks, had a good diet, took some good protein. push ups will have you on swole. but dont cheat yourself.
go out for a run. 10 or 20 minute run, you would be surprised how fresh you will feel afterwards.