The effect of Functional Electrical Stimulation-assisted posture-shifting in bone mineral density: case series-pilot study.

STUDY DESIGN: A training intervention study using standing dynamic load-shifting Functional Electrical Stimulation (FES) in a group of individuals with complete spinal cord injury (SCI) T2 to T10. OBJECTIVES: Investigate the effect of FES-assisted dynamic load-shifting exercises on bone mineral density (BMD). SETTING: University Lab within the Biomedical Engineering METHODS: Twelve participants with ASIA A SCI were recruited for this study. Three participants completed side-to-side load-shifting FES-assisted exercises for 29 ± 5 weeks, 2× per week for 1 h, and FES knee extension exercises on alternate days 3× per week for 1 h. Volumetric Bone Mineral density (vBMD) at the distal femur and tibia were assessed using peripheral quantitative computed tomography (pQCT) before and after the intervention study. RESULTS: Participants with acute and subacute SCI showed an absolute increase of f trabecular vBMD (vBMDTRAB) in the proximal (mean of 26.9%) and distal tibia (mean of 22.35%). Loss of vBMDTRAB in the distal femur was observed. CONCLUSION: Improvements in vBMDTRAB in the distal tibia were found in acute and subacute SCI participants, and in the proximal tibia of acute participants, when subjected to anti-gravity FES-assisted load-bearing exercises for 29 ± 5 weeks. No vBMD improvement in distal femur or tibial shaft were observed in any of the participants as was expected. However, improvements of vBMD in the proximal and distal tibia were observed in two participants. This study provides evidence of an improvement of vBMDTRAB, when combining high-intensity exercises with lower intensity exercises 5× per week for 1 h.

Tibiofemoral forces during FES rowing in individuals with spinal cord injury.

The purpose of this study is to determine the tibiofemoral forces during functional electrical stimulation (FES) rowing in individuals with spinal cord injury (SCI). We analysed the motion of five participants with SCI during FES rowing, with simultaneous measurements of (i) three-dimensional marker trajectories, (ii) foot reaction forces (FRFs), (iii) ergometer handle forces, and (iv) timestamps for electrical stimulation of the quadriceps and hamstrings muscles. We created full-body musculoskeletal models in OpenSim to determine subject-specific tibiofemoral forces during FES rowing. The peak magnitudes of tibiofemoral forces averaged over five participants with SCI were 2.43 ± 0.39 BW and 2.25 ± 0.71 BW for the left and right legs, respectively. The peak magnitudes of FRFs were 0.19 ± 0.04 BW in each leg. The peak magnitude of handle forces was 0.47 ± 0.19 BW. Peak tibiofemoral force was associated with peak FRF (magnitudes, R2 = 0.56, p = 0.013) and peak handle force (magnitudes, R2 = 0.54, p = 0.016). The ratios of peak magnitude of tibiofemoral force to peak magnitude of FRF were 12.9 ± 1.9 (left) and 11.6 ± 2.4 (right), and to peak magnitude of handle force were 5.7 ± 2.3 (left) and 4.9 ± 0.9 (right). This work lays the foundation for developing a direct exercise intensity metric for bone mechanical stimulus at the knee during rehabilitation exercises. Clinical Significance: Knowledge of tibiofemoral forces from exercises such as FES rowing may provide clinicians the ability to personalize rehabilitation protocols to ensure that an SCI patient is receiving the minimum dose of mechanical stimulus necessary to maintain bone health.

Bone changes in the lower limbs from participation in an FES rowing exercise program implemented within two years after traumatic spinal cord injury.

Objective: To determine the effect of a functional electrical stimulation (FES) rowing program on bone mineral density (BMD) when implemented within two years after SCI.Design: Prospective.Setting: Health Care Facility.Participants: Convenience sample; four adults with recent (<2 years) traumatic, motor complete SCI (C7-T12 AIS A-B).Intervention: A 90-session FES rowing exercise program; participants attended 30-minute FES training sessions approximately three times each week for the duration of their participation.Outcome Measures: BMD in the distal femur and tibia were measured using peripheral Quantitative Computed Tomography (pQCT) at enrollment (T0) and after 30 (T1), 60 (T2), and 90 (T3) sessions. Bone stimulus was calculated for each rower at each time point using the average number of weekly loading cycles, peak foot reaction force, and bone mineral content from the previous time point. A regression analysis was used to determine the relationship between calculated bone stimulus and change in femoral trabecular BMD between time points.Results: Trabecular BMD in the femur and tibia decreased for all participants in T0-1, but the rate of loss slowed or reversed between T1-2, with little-to-no bone loss for most participants during T2-3. The calculated bone stimulus was significantly correlated with change in femoral trabecular BMD (P = 0.016; R2 = 0.458).Conclusion: Consistent participation in an FES rowing program provides sufficient forces and loading cycles to reduce or reverse expected bone loss at the distal femur and tibia, at least temporarily, in some individuals within two years after SCI.Trial Registration: NCT02008149.

Novel instrumented frame for standing exercising of users with complete spinal cord injuries.

This paper describes a Functional Electrical Stimulation (FES) standing system for rehabilitation of bone mineral density (BMD) in people with Spinal Cord Injury (SCI). BMD recovery offers an increased quality of life for people with SCI by reducing their risk of fractures. The standing system developed comprises an instrumented frame equipped with force plates and load cells, a motion capture system, and a purpose built 16-channel FES unit. This system can simultaneously record and process a wide range of biomechanical data to produce muscle stimulation which enables users with SCI to safely stand and exercise. An exergame provides visual feedback to the user to assist with upper-body posture control during exercising. To validate the system an alternate weight-shift exercise was used; 3 participants with complete SCI exercised in the system for 1 hour twice-weekly for 6 months. We observed ground reaction forces over 70% of the full body-weight distributed to the supporting leg at each exercising cycle. Exercise performance improved for each participant by an increase of 13.88 percentage points of body-weight in the loading of the supporting leg during the six-month period. Importantly, the observed ground reaction forces are of higher magnitude than other studies which reported positive effects on BMD. This novel instrumentation aims to investigate weight bearing standing therapies aimed at determining the biomechanics of lower limb joint force actions and postural kinematics.

Development of Functional Electrical Stimulation Rowing: The Rowstim Series.

Potentially, functional electrical stimulation (FES)-assisted exercise may have an important therapeutic role in reducing comorbidities associated with spinal cord injury (SCI). Here, we present an overview of these secondary life-threatening conditions, discuss the rationale behind the development of a hybrid exercise called FES rowing, and describe our experience in developing FES rowing technology. FES rowing and sculling are unique forms of adaptive rowing for those with SCI. The paralyzed leg musculature is activated by multiple channels of electrical pulses delivered via self-adhesive electrodes attached to the skin. The stimulated muscle contractions are synchronized with voluntary rowing movements of the upper limbs. A range of steady-state FES rowing exercise intensities have been demonstrated from 15.2 ± 1.8 mL/kg/min in tetraplegia to 22.9 ±7.1 mL/kg/min in paraplegia. We expect that such high levels may help some to achieve significant reductions in the risks to their health, particularly where a dose-response relationship exists as is the case for cardiovascular disease and Type II diabetes. Furthermore, preliminary results suggest that cyclical forces more than 1.5 times body weight are imposed on the leg long bones which may help to reduce the risk of fragility fractures. We have demonstrated the feasibility of FES rowing on land and water using adapted rowing technology that includes; a fixed stretcher indoor ergometer (adapted Concept 2, Model E), a floating stretcher indoor ergometer (adapted Concept 2 Dynamic), a turbine powered water rowing tank, a custom hydraulic sculling simulator and a single scull (adapted Alden 16). This has involved volunteers with paraplegia and tetraplegia with SCI ranging from C4 to T12 AIS A using at least 4-channels of surface electrical stimulation. FES rowers, with SCI, have competed alongside non-SCI rowers over the Olympic distance of 2000 m at the British Indoor Rowing Championships in 2004, 2005, and 2006 and the World Indoor Rowing Championships in 2006 (CRASH-B's) in Boston, MA, USA. The best 2000 m FES rowing performance to date has been achieved by a 23-year-old male, Tom Aggar T12 AIS A, in 10 min 28 s. Moreover, two of our FES rowers with complete paraplegia have gone on to successfully compete in the Adaptive Rowing arms-only category (AM1x) at the World Rowing Championships and Paralympic Games.

FES-rowing attenuates bone loss following spinal cord injury as assessed by HR-pQCT.

Neurologically motor complete spinal cord injury (SCI) presents a unique model of bone loss whereby specific regional sites are exposed to a complete loss of voluntary muscle-induced skeletal loading against gravity. This results in a high rate of bone loss, especially in the lower limbs where trabecular bone mass decreases by ~50-60% and cortical bone mass decreases by 25-34% before the rate of bone loss slows. These SCI-induced losses that are likely superimposed on continual age-related bone losses, increase the risk of low-impact fragility fracture. The fracture incidence 20 years post SCI is reported to be 4.6% per year. An intervention that effectively prevents, attenuates, or reverses bone loss is therefore highly desirable. We present a case study of an individual with chronic complete SCI, where bone loss has been attenuated following long-term functional electrical stimulation (FES)-rowing training. In this case study, we characterize the ultradistal tibia and ultradistal radius of the FES-rower with chronic complete SCI using high-resolution-peripheral quantitative computed tomography. These data are compared with a group of FES-untrained individuals with chronic complete SCI and to a normative non-SCI cohort. The evidence suggests, albeit from a single individual, that long-term FES-rowing training can attenuate bone loss secondary to chronic complete SCI. Indeed, key FES-rower's bone metrics for the ultradistal tibia more closely resemble normative age-matched values, which may have clinical significance since the majority of fragility fractures in chronic SCI occur in the lower extremities.

A Design Method for FES Bone Health Therapy in SCI.

FES assisted activities such as standing, walking, cycling and rowing induce forces within the leg bones and have been proposed to reduce osteoporosis in spinal cord injury (SCI). However, details of the applied mechanical stimulus for osteogenesis is often not reported. Typically, comparisons of bone density results are made after costly and time consuming clinical trials. These studies have produced inconsistent results and are subject to sample size variations. Here we propose a design process that may be used to predict the clinical outcome based on biomechanical simulation and mechano-biology. This method may allow candidate therapies to be optimized and quantitatively compared. To illustrate the approach we have used data obtained from a rower with complete paraplegia using the RowStim (III) system.

Consistency among musculoskeletal models: caveat utilitor.

Musculoskeletal simulation software and model repositories have broadened the user base able to perform musculoskeletal analysis and have facilitated in the sharing of models. As the recognition of musculoskeletal modeling continues to grow as an engineering discipline, the consistency in results derived from different models and software is becoming more critical. The purpose of this study was to compare eight models from three software packages and evaluate differences in quadriceps moment arms, predicted muscle forces, and predicted tibiofemoral contact forces for an idealized knee-extension task spanning -125 to +10° of knee extension. Substantial variation among models was observed for the majority of aspects evaluated. Differences among models were influenced by knee angle, with better agreement of moment arms and tibiofemoral joint contact force occurring at low to moderate knee flexion angles. The results suggest a lack of consistency among models and that output differences are not simply an artifact of naturally occurring inter-individual differences. Although generic musculoskeletal models can easily be scaled to consistent limb lengths and use the same muscle recruitment algorithm, the results suggest those are not sufficient conditions to produce consistent muscle or joint contact forces, even for simplified models with no potential of co-contraction.