My daughter was two weeks old and forcefully lifting her head to look around. I was told by a doctor that babies that young aren't supposed to be able to do that. Where there's a will, there's a way!
DD9 did this on day one (though in her case it looked less "forceful" than "casual", and she held it up for several seconds before lying back down), which I witnessed just a few hours after she popped her own shoulder and arm out of DW (injuring DW in the process), and attempted to use her liberated arm to push herself out the rest of the way. We still have the gasps of astonishment from the assembled medical professionals on tape.
DD would make an interesting case study for gauging the strength of infants, as she still has much more muscle mass than her age peers. Watching other kids try to push her off the ball in soccer is quite entertaining.
