A recent 3-year study suggests 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 spinal cord injury (SCI) patients. Researchers of the Iowa City-based University of Iowa (UI) reportedly conducted the clinical trial, which focused on measuring the effective dose of load and testing the impact of different doses of load in patients with paralysis. A news release notes that Richard Shields, PT, PhD, professor and director of the UI physical therapy and rehabilitation science graduate programs, led the study.

According to researchers, the study analyzed the effects of load applied during assisted standing with electrical stimulation, assisted standing with no electrical stimulation, and the effect of sitting without applied load. The study compared the effect of “high dose” loads of 150% of body weight, which was induced by electrically stimulating the quadriceps muscle in one leg while the patient was supported in a standing position, with a "low dose,” load of 40% body weight, which involved assisted standing with no electrical stimulation, and a “no dose” load of 0% percent body weight, with the patient sitting.

Researchers say study participants were asked to perform their training five times per week for 3 years and had their bone mineral density and muscle strength tested several times over the study’s duration. Shields explains that in the study’s findings, “When we applied a load of 1.5 times their body weight using electrical stimulation of the quadriceps muscle we saw a significant impact on the bone density as well as the expected growth of the skeletal muscle.” 

The results suggest that after 3 years, the average bone density in the femur was almost 40% lower in patients who received a low dose or no dose load compared to patients who received a high dose. The results also specifically indicate that high dose load may slow the deterioration of the trabecular bone.

“Keeping 40% of the bone material in the bone should translate into improved overall health among along several dimensions, including reducing the risk of fracture, as well as reducing other common complications stemming from SCI, like kidney stones and diabetes,” Shields explains. He adds that the study’s results provide, “evidence that there is a mechanical dose of load through muscle force that the skeleton can respond to that has an effect.”

Source: University of Iowa