Loss of bone density leads to brittle bones that fracture easily. It is a major complication of spinal cord injury (SCI), which affects about 250,000 Americans every year.
A new clinical trial conducted by University of Iowa researchers shows that delivering high doses of "load," or stress, to bone through programmed electrical stimulation of the muscle significantly slows the loss of bone density in patients with SCI.
The focus on quantifying the effective dose of load is one of the study's most important aspects, says Richard Shields, P.T., Ph.D., a professor and director of the UI Physical Therapy and Rehabilitation Science Graduate Programs. The study also is the first to carefully test the impact of different doses of load in humans with paralysis.
Previous research had suggested that stressing or loading bone through muscle contractions could slow the loss of bone density, but results from clinical trials have been mixed.
"Thirty years ago a clinical trial concluded that putting patients with SCI in an upright weight-bearing position with braces or standing frames did nothing to prevent loss of bone density," Shields says. "The novelty of our study is we have designed a method for individuals with paralysis to stand (bear weight) while superimposing a dose of muscle force using programmed electrical stimulation of the muscle."
The study findings, published in the journal Osteoporosis International in December 2011, reveal that only high "doses" of muscle force are effective for significantly reducing bone loss.
"The previous studies, without muscle activation, were like doing a drug trial where the dose of drug was too low, or below 'therapeutic threshold,' to cause an effect," Shields explains.
The UI researchers have also recently shown that the electrical stimulation strengthens muscle by activating genes that promote muscle growth and endurance, and improve glucose metabolism.
|Contact: Jennifer Brown|
University of Iowa Health Care