well many times i've heard that push-ups,sit-ups,crunches and such exercices are better(healthier too) and much more useful than lifting weights and doing exercices on gym machines.well i was just interested if that is true and why.i would also like to know how much more is gym workout effective than home workout(push-ups,sit-ups,etc).for example if i lift 50 kilos about 8 times,is it much more effective than doing 25-30 push-ups,if you know what i mean.thanks.