I don't see the benefit of turning your palms inward at the finish. If you want to work your tricepts more extensively, perform the ENTIRE MOTION of the DB press with palms facing inward. Regular form will hit the chest more. This guy might be attempting to feel a better squeeze at the top - however, as other people may tell you, squeezing at the top with dumbbells doesn't do much because it releases tension from the contraction. Instead, go straight up and down (with a very slight squeeze if needed).
__________________ "Before I'd get in the ring, I'd have already won or lost it on the road. The real part is won or lost somewhere far away from witnesses - behind the lines, in the gym and out there on the road, long before I dance under those lights." -- Muhammad Ali |