For functional strength training I prefer to focus primarily on teaching the core to hold tight and prevent unwanted movement of the spine, ribs, and pelvis. (weckmethod.com)
The best way of preventing unwanted movement is to strap your baby in the swing. (babygearspecialist.com)
The bezel and metal body have very little unwanted movement, and it doesn't feel too tight against the wrist. (techradar.com)