Its simple really. Just get your lazy bum out of the bed and start moving. Only then you will see improvements. If you can get up out of bed then you can do a sit up. If you can sit on a chair then the next step will be situps. Life is all about working out. Wether you have a 6 pack or a one pack(like me). You can always improve by doing things you normally do with 100% of effort.
