A healthy vestibular system is one thing that declines with lack of use.  I would suggest that anyone who gets motion sickness start with small amounts of vestibular activity, just a couple of seconds, and build up.

One of the things you see in the frail elderly is that tendency to feel like they are falling and then actually falling easily.  They can become nervous, reduce overall activity and risk taking, and age even more quickly.

ON the other hand I had a 75 year old teacher in New York, Irmgard Bartenieff, who could spin, jump in the air, twist, land back down on the floor and spiral back up to standing.  She walked 40 New York blocks to work every day (and back home), took Tai Chi and other martial arts.  Because she never stopped moving she was vital her whole life.  She was not ill until the disease that killed her.  We should all be so healthy.  One way to stay that healthy is to constantly keep your vestibular system working by doing the assignment your kids do.  If you have vestibular issues you can heal them by doing vestibular activities.