I seem to enjoy incorporating a backwards step into the reactions of my characters, as again in this task where our characters had to react in shock to something on their phone, I made my character do exactly this. I wanted them to first move in towards the phone, instead of bringing the phone to their face, where perhaps the phone has become an object of weight in the metaphorical weight in light of what the character is reacting to. I wanted this motion to be contained and inquisitive, displayed both in their facial expression and their initial small movement. The character then leaps out, stepping backwards, their face wide and shocked in the face of whatever horror has appeared on their phone. I think to improve upon this I could add more frames to smooth out the movement, and perhaps exaggerate the shocked motion more, bring the arms out further, perhaps moving the character backwards more, and bending their knees in an attempt to steady their self in this motion.
I wanted for this double take, to have the character first glimpse the camera with a small side eye and head movement, then for the whole body to react in shock at whatever might be in that direction. I think the initial glimpse could be a little more nonchalant, with a smaller less obvious movement, perhaps with just a movement of the eyes, and the later reaction could happen quicker, perhaps even so much that the character follows through, overturning, and having to bring the body round again slightly.