Small vibrations can improve bone, increase muscle mass

Content provided by the Faculty of the Harvard Medical School

Small vibrations can improve bone, increase muscle mass

Physical exercise is one of the principal recommendations for preventing and treating osteoporosis, but its effects are hard to assess. No one knows exactly how much of what type of exercise is needed to stimulate bone growth or counteract age-related bone loss, and not everyone responds the same way to the same physical activities. Most exercise programs result in modest bone density gains, about 1%–2%, in premenopausal women; in postmenopausal women, bone benefits are generally measured in bone mass preserved, not gained.

Moderate- to high-intensity regimens can work, but few adults can comply with them long-term, and women who have osteoporosis or are frail or disabled simply cannot participate in them. Most patients must rely on long-term drug therapy, but with the exception of parathyroid hormone, these medications don't actually stimulate new bone formation.

A new way to preserve and possibly build new bone involves simply standing for a few minutes a day on a gently oscillating platform the size and shape of a bathroom scale. Research thus far suggests that it can do at least as much for bone density as longer bouts of vigorous exercise, and it appears to strengthen bone literally from the inside out.

Encouraging research

The strategy, which has produced good results in mice, rats, and sheep, is undergoing human trials in the United States and around the world. Such trials are showing that exposure to small, barely perceptible vibrations can prevent bone loss, increase bone mass, and build muscle.

Potential applications include not only osteoporosis treatment and prevention but also therapy for people with muscle- or bone-wasting conditions such as cerebral palsy, muscular dystrophy, and digestive disorders that rob the body of calcium and other nutrients. The National Aeronautics and Space Administration is also interested in vibration therapy as a way to counter the bone loss and muscle atrophy that result from lengthy space flight.

Most of the research on oscillating plate therapy has been led by investigators at the State University of New York (SUNY) at Stony Brook. They collaborated on a randomized trial carried out at Children's Hospital in Los Angeles involving 48 young women ages 16–21 who had low bone density and were at risk for developing low peak bone mass (and osteoporosis later in life). Half the women were assigned to stand on the oscillating plate for 10 minutes every day for a year; there was no placebo or intervention for the other half.

Photo courtesy of Juvent, Inc.

After one year, CT scans showed improvements in the treated women in trabecular (interior) bone at the spine and cortical (outer) bone at the hip — changes that are consistent with stronger bone. Overall, bone density increased by 3% (there was no change in the control group) and adjacent muscle mass improved by 4%. This is the first study to measure and show changes in muscle following low-magnitude vibration stimulation. The results were presented at the September 2005 meeting of the American Society for Bone and Mineral Research.

In 2004, the SUNY-Stony Brook group reported results of a trial they helped conduct involving 70 postmenopausal women treated at Creighton University's Osteoporosis Research Center who were randomly assigned to two 10-minute sessions per day on either the oscillating plate or a placebo device. After a year, the group of women using the real oscillating plate experienced a 2%–3% advantage over the placebo group in preserving bone at the spine and hip (Journal of Bone and Mineral Research, March 2004). A related study involving children with cerebral palsy, who are prone to inactivity-related bone fragility, found that using the oscillating plate — even at half the prescribed duration — resulted in a 17% net improvement in trabecular bone density measured in the tibia, the large leg bone between the knee and the foot (Journal of Bone and Mineral Research, published online, January 27, 2004).

How does it work?

Small vibrations mimic what muscle cells do during common activities such as standing, maintaining balance, and walking. They twitch in sequence, making lots of tiny contractions that exert many small stresses on the bone. This can result in bone-building activity. According to Clinton T. Rubin, Ph.D., principal investigator of the SUNY–Stony Brook research, such low-magnitude strains can influence bone strength at least as much as bursts of larger-strain activities like vigorous exercise. He cautions, however, that not all vibrations are good vibrations. Vibration machines that are promoted to enhance athletic training often operate at amplitudes and frequencies that exceed official tolerance limits and could damage not only bone and connective tissue but also cardiovascular and neurological systems.

Rubin's group has determined that small accelerations — 0.3 g, meaning gravitational force — at a frequency of 30 Hz (or cycles per second) are safe and effective when delivered for 10 minutes a day, 5 days a week. This level of vibration is programmed into an investigational oscillating plate developed by a company that the researchers helped start, called Juvent, Inc. A large clinical trial is being planned to gather the data required for FDA approval of the device in the United States, although the machine will be marketed in other countries by the end of 2005.

No data are available yet on whether oscillating plate therapy reduces fracture rates. Nor has the device been tested directly against specific exercise regimens or osteoporosis drugs. Even if the oscillating plate proves itself in larger studies, that doesn't mean we should abandon our sneakers and Pilates classes — our bones aren't the only beneficiaries of phys­ical activity. But it does suggest that women who are vulnerable to fractures or can't engage in vigorous workouts may be able to reap some of the same benefits vigorous exercisers do.

Last updated:	September 05, 2008