The jarring forces of high-impact aerobics can cause damage to the delicate structures of the inner ear, new research suggests.
Those afflicted suffer from symptoms including imbalance, vertigo, ringing in the ears and even hearing loss. These complaints can persist long after the victim has left the gym and may be permanent.
High-impact aerobics classes have extended periods of arduous jumping and bobbing. In low-impact aerobics classes, one foot always remains on the floor.
Scientists theorize that excess jarring may disrupt tiny granules called otoliths that transmit information about orientation to the brain. The small spiral called the cochlea, involved in hearing, may also be affected, they suggest.
A letter published in last week's New England Journal of Medicine reported on five previously healthy women with clear symptoms of inner-ear damage who were examined by Dr. Michael A. Weintraub, a professor of neurology at New York Medical College.
All were devotees of high-impact aerobic classes; three of the five were instructors. Extensive tests ruled out more serious causes for their complaints, like multiple sclerosis or a brain tumor.
"People are bouncing up and down continuously and the vibrations are transmitted to the skull and tiny bones of the inner ear," said Dr. Weintraub.
"If you do this to a significant degree, you may disturb the fine-tuning mechanism for balance. I believe high-impact aerobics can do that."