Is it normal to hear your implant when you move your arm up and down?

At this point you are
early in the healing process. This is not uncommon at this point. Your implants will continue to settle and soften
with time. Follow up with your surgeon as directed.
Regards,

Hearing it move around inside at 4 days may be related to fluid in the pocket.  But at 4 days you are very early in the healing process and need to give it time.

Thanks for your question.No worries.  It is totally normal.  Caused by fluid around the implant's shell (not the air) making the swishing noise.  Dissipates a week to two weeks after the procedure.  You may find when at higher altitudes (skiing in Colorado etc), the sound returns a few days after you get there.  It disappears after you return to a lower altitude, or if you stay at the higher altitude for a week.Enjoy

Swishing of the implant can be from residual air in the pocket or possibly some fluid.It should disappear over the next week or so.

At 4 days post op it is not uncommon to hear sounds.  This is caused from air in the breast pocket.  This will resolve itself over time. 

It s common this early to hear unusual sounds after breast implants. This can be crepitus from air inside the pocket which will dissappear soon.