I think I recall a lot of muscle soreness when I first started pushups, do note, I think I was unable to get even one pushup back then. Soreness is going to be normal, get used to it, if you want pig pecs you need to do flat benching, and deadlifting, eat enough calories and protein to fuel it.
Diet is key, Diet is key, what you eat is what you be, Diet is key. Get all your calories from whole foods (un-modified foods), except your post workout shake.
If you don't have a bench then you can floor press by raising the bar up about 1.5 ft and do it that way.
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Even when you start benching, the pushups are beneficial to you and there are plenty of variations to keep you busy. Standard pushups aren't going to pack on a lot of muscle as far as I know. I'm not sure about the more advanced versions, they demand a lot of strength though, like the planc pushup, hand stand pushup, etc.
There are big threads around here packed with everything you need to know, forget where they are.. ah here is one of them.
http://www.discussbodybuilding.com/tm.aspx?high=&m=111173&mpage=1#111173 I think you get sore from using a muscle really hard or from an angle you don't/haven't really used it from before.
<message edited by thunderblood on Saturday, January 03, 2009 10:54 AM>