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January 18, 2011

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Daily vibration may help protect aging bones

Oct. 26, 2010
Courtesy of Medical College of Georgia 
and World Science staff

Dai­ly, whole-body vibra­t­ion may re­duce the bone dens­ity loss that usu­ally oc­curs with age, re­search­ers re­port based on a mouse stu­dy.

The sci­en­tists found that 12 weeks of dai­ly, 30-minute ses­sions in 18-month old male mice seemed to fore­stall the an­nu­al loss that can lead to frac­tures, dis­abil­ity and death. The ro­dents were equiv­a­lent in age to 55- to 65-year-old hu­mans, added the in­ves­ti­ga­tors, bi­o­med­i­cal en­gi­neer Karl H. Wenger of the Med­i­cal Col­lege of Geor­gia and col­leagues.

Re­port­ing the find­ings in the re­search jour­nal Bone, they added that vibra­t­ion im­proved dens­ity around the hip joint with a shift to­ward high­er dens­ity in the fe­mur, the long bone of the leg. The in­ves­ti­ga­tors al­so found a re­duc­tion in body lev­els of a sub­stance as­so­ci­at­ed with bone break­down and an in­crease in the sur­face ar­ea in­volved in bone forma­t­ion in the vi­brat­ed mice.

The find­ings pro­vide new ev­i­dence that the tech­nique, which dates back to the 1800s and is now show­ing up in homes, gyms and re­ha­bilita­t­ion clin­ics, has bone ben­e­fit, par­tic­u­larly as a low-risk op­tion for in­jured peo­ple with lim­it­ed mo­bil­ity, Wenger said.

The sci­en­tists the­o­rize that the rhyth­mic move­ment, which pro­duces a sensa­t­ion si­m­i­lar to that of a vi­brat­ing cell phone but on a larg­er scale, ex­er­cises cells so they work bet­ter. Vibra­t­ion prompts move­ment of the cell nu­cle­us, which is sus­pended by nu­mer­ous thread­like fibers called fil­a­ments. “The fil­a­ments get all de­formed like springs and then they spring back,” Wenger said.

All the move­ment re­leases sub­stances called tran­scrip­tion fac­tors that spur the forma­t­ion of new os­teo­blasts, the cells that make bone, Wenger and col­leagues ex­plained. With age, the bal­ance of bone pro­duc­tion and de­struc­tion – by os­teo­clasts – tips to the loss side.

In the case of an in­ju­ry, vibra­t­ion acts on stem cells, the mas­ter con­trollers of the heal­ing pro­cess, he added. “We think that in frac­ture heal­ing, you get a more dra­mat­ic re­sponse. We don’t know ex­actly why it af­fects the bi­ol­o­gy dif­fer­ently but it’s likely be­cause of the ex­tent to which stem cells in­vade the in­jured ar­ea,” Wenger said. His team al­so found that vibra­t­ion slows stem cell pro­lifera­t­ion, which may not make sense at first glance, they not­ed, but likely means more stem cells dif­fer­entiate in­to bone cells rath­er than con­tin­u­ing to just make more stem cells.

To see if their find­ings trans­late to the trau­ma clin­ic, the re­search­ers are eval­u­at­ing vibra­t­ion tol­er­ance in pa­tients with lower-limb frac­tures. The in­vesti­ga­tors said they’re find­ing, sur­pris­ing­ly, that even two weeks af­ter in­ju­ry the sub­tle vibra­t­ion is sooth­ing, rath­er than pain­ful, to most.

The sci­en­tif­ic team added that in pre­vi­ous re­search by Clin­ton T. Ru­bin at the State Uni­vers­ity of New York at Stony Brook, post-menopausal wom­en at the peak age of bone de­cline ex­pe­ri­enced re­sults si­m­i­lar to those of the ag­ing mice. Wenger’s stud­ies used only male mice so that ef­fects such as fluc­tu­at­ing hor­mones would­n’t af­fect the re­sults. 

While vibra­t­ion lacks the same car­di­o­vas­cu­lar ben­e­fit of ex­er­cise, an­i­mal and hu­man stud­ies al­so have shown it can im­prove mus­cle strength and weight loss, ac­cord­ing to Wenger and col­leagues.

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Daily, whole-body vibration may help reduce the usual bone density loss that occurs with age, researchers report based on a mouse study. The scientists found that 12 weeks of daily, 30-minute sessions in 18-month old male mice seemed to forestall the expected annual loss that can lead to fractures, disability and death. The mice were equivalent in age to 55- to 65-year-old humans, added the investigators, biomedical engineer Karl H. Wenger of the Medical College of Georgia and colleagues. Reporting the findings in the research journal Bone, they added that vibration improved density around the hip joint with a shift toward higher density in the femur, the long bone of the leg. The investigators also found a reduction in body levels of a substance associated with bone breakdown and an increase in the surface area involved in bone formation in the vibrated mice. The findings provide new evidence that the technique, which dates back to the 1800s and is now showing up in homes, gyms and rehabilitation clinics, has bone benefit, particularly as a low-risk option for injured people with limited mobility, Wenger said. The scientists theorize that the rhythmic movement, which produces a sensation similar to that of a vibrating cell phone but on a larger scale, exercises cells so they work better. Vibration prompts movement of the cell nucleus, which is suspended by numerous threadlike fibers called filaments. “The filaments get all deformed like springs and then they spring back,” Wenger said. All the movement releases substances called transcription factors that spur the formation of new osteoblasts, the cells that make bone, Wenger and colleagues explained. With age, the balance of bone production and destruction – by osteoclasts – tips to the loss side. In the case of an injury, vibration acts on stem cells, the master controllers of the healing process, he added. “We think that in fracture healing, you get a more dramatic response. We don’t know exactly why it affects the biology differently but it’s likely because of the extent to which stem cells invade the injured area,” Wenger said. They also found that vibration slows stem cell proliferation, which may not make sense at first glance, they noted, but likely means more stem cells differentiate into bone cells rather than continuing to just make more stem cells. To see if their findings translate to the trauma clinic, the researchers said they’re evaluating vibration tolerance in patients with lower-limb fractures and finding, surprisingly, that even two weeks after injury the subtle vibration is soothing, rather than painful, to most. The scientific team added that in previous research by Clinton T. Rubin at the State University of New York at Stony Brook, post-menopausal women at the peak age of bone decline experienced results similar to those of the aging mice. Wenger’s studies used only male mice so that effects such as fluctuating hormones wouldn’t affect the results. While vibration lacks the same cardiovascular benefit of exercise, animal and human studies also have shown it can improve muscle strength and weight loss, according to Wenger and colleagues.