If you are unfit and can't do a push up and a friend said to hold the up position for 30 seconds to build up strength to actually do a pushup so how many reps and sets should i hold it for?
I'd do as many as I could the first time. After that point, try to do one more each day, taking a day off every three or four days. After a couple of weeks, add a few push-ups to the mix.
