http://searchwarp.com/swa5933.htm
"The natural skating position of the Heelys forces the neck to push the head outwards to balance a body that is now poised to fall backwards. The neck and shoulder muscles are strained to push the head forward to counteract gravity. However, our neck muscles were not made to hold our head out on a horizontal plane. This is a stop gap measure by our body to prevent us from toppling. Sadly, the damage is not going to be stop gap nor temporary"
"The skating position of the Heelys compels the lumbar curve of our backs to flex AGAINST its natural curve, creating a flat lower back instead of a concave one."
"Constant walking on shoes that pivot on rollers (now that wheels have taken the place of the heels) conditions our gait muscles to walk in a manner contrary to natural stride patterns. This leads to knee, shin and foot injuries later in life."
http://www.cbsnews.com/stories/2006/03/03/earlyshow/living/parenting/main1365761.shtml
"Brzezinski spoke with Valerie Poston of San Diego, whose nine-year-old daughter, Katrina, suffered a concussion when she lost her balance wearing Heelys at a mall.
"It just didn't dawn on me that they were so dangerous," Valerie told Brzezinski, adding she never thought twice about letting her girls wear Heelys.
Katrina's sister says, "My sister took a few steps, and then her foot just slipped out from under her and she just fell back."
"We both heard the big thump, terrible, terrible thump," says Valerie, "and we came running and found her on the floor crying, holding the back of her head."