Using Musculoskeletal Models to Assess FES Rowing for Skeletal Health After SCI

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DESCRIPTION (provided by applicant): The Veterans Health Administration is believed to be the largest single provider of health care to individuals with spinal cord injury (SCI) in the United States. In 2004 alone, the direct medical costs associated with the care of VA patients with SCI exceeded $700 million. The estimated lifetime healthcare cost for a single 25- year-old individual with high tetraplegia is $4.5 million and increasing yearly. A common condition that contributes to that high cost is disuse-related osteoporosis and pathologic fracture requiring prolonged hospitalization. Maintaining skeletal health in the lower limbs of individuals with SCI is universally recognized as a highly desirable clinical goal, however, that goal has proven difficult to achieve. Neither pharmacologic nor non-pharmacologic treatments have produced particularly encouraging results in clinical trials to date. A recent comprehensive review of non-pharmacological treatments for modulating bone loss after SCI found that high-intensity exercises using functional electrical stimulation (FES) of the lower limbs can have a beneficial effect on bone. A key conclusion from that review is that the duration of training and the intensity of the mechanical stimulus within the bone appear to be key factors in reducing bone loss. In the only study on the effect of bone density from FES-rowing that has appeared in the literature to date, researchers in England in 2011 reported increased bone density at the femoral neck in one individual who is 12-years post SCI and who is an avid FES-rower. Recently those same researchers shared preliminary results that demonstrate remarkable bone preservation in the trabecular bone at the proximal tibia of the same individual. However, it remains unknown if the same benefits to skeletal health can be widely achieved in other individuals participating in a clinically practicable, rowing intervention program. Furthermore, the dissimilar outcomes that have been reported for other non-pharmacological interventions suggest that differences among patients in muscle conditioning and fatigue during electrical stimulation must be taken into consideration when designing a specific intervention protocol, i.e., number of exercise sessions per week, rowing intensity, for a given patient. Given the paucity of data on the effect of FES-rowing on bone density, we are proposing an FES-rowing study that specifically focuses on bone health. The long-term goal of this area of research is to reduce the incidence of fracture from disuse-osteoporosis in the lower limbs of individuals with spinal cord injuries. The objective of the pilot phase of this long-term endeavor is to determine if FES-rowing can prevent or significantly attenuate bone loss in the lower limbs in individuals with acute and sub-acute SCI. In this pilot phase we will address two questions: 1) can the positive benefits from FES-rowing previously found in one individual with SCI be repeated in a larger group of individuals with a clinically reasonable intervention duration; and 2) can the inter-individual differences in osteogenic response following a rowing intervention be explained by the differences in skeletal force histories from the rowing intervention? Our pilot study has four specific aims: 1) to acquire a state-of-the-art FES-assisted rowing system; 2) to collect kinematic and kinetic data for a pilot group of individuals with spinal cord injury performing FES-assisted rowing; 3) to use musculoskeletal simulation tools to estimate subject-specific skeletal forces during rowing; and 4) to use bone adaptation theory to evaluate the potential of FES-rowing to moderate bone loss based on the subject-specific musculoskeletal models and subject-specific FES-rowing histories. At the conclusion of this pilot study we expect to have evidence to show that an FES-rowing exercise regimen that generates a sufficient skeletal loading history can have a significant effect on reducing bone loss following SCI. If successful, this will represent a key demonstration that FES-rowing has a skeletal benefit not yet matched by other exercise modalities. Equally as important, we expect our results will make a fundamental contribution to the understanding of the loading history that is required to alter that natural history of bone loss following SCI.