I was just wondering how much less effective is, say, a standard flat bench press on a Smith machine as opposed to 100% free weight barbell? the reason I ask is because this is my third week back in the gym after a small layoff, so I have been doing bench with the Smith Machine in order to built my core strength, stability and get that balance back before I jump into what I prefer doing; dumbell bench. I am afraid if I start lifting heavy dumbells this soon I might hurt my shoulders or something so I am playing it safe.

But anyway, is the Smith version a lot less effective than the [b]barbell[b] ?