Effects of cycling and/or electrical stimulation on bone mineral density in children with spinal cord injury.

STUDY DESIGN: Randomized clinical trial. OBJECTIVES: To determine the effect of cycling and/or electrical stimulation on hip and knee bone mineral density (BMD) in children with spinal cord injury (SCI). SETTING: Children's hospital specializing in pediatric SCI. METHODS: A total of 30 children, aged 5-13 years, with chronic SCI were randomized to one of three interventions: functional electrical stimulation cycling (FESC), passive cycling (PC), and non-cycling, electrically stimulated exercise (ES). Each group exercised for 1 h, three times per week for 6 months at home. The hip, distal femur and proximal tibia BMD were examined via dual-energy X-ray absorptiometry (DXA) pre- and post-intervention. RESULTS: In all, 28 children completed data collection. The FESC group exhibited increases in hip, distal femur and proximal tibia BMD of 32.4, 6.62 and 10.3%, respectively. The PC group exhibited increases at the hip (29.2%), but no change at the distal femur (1.5%) or proximal tibia (-1.0%). The ES group had no change at the hip (-0.24%) and distal femur (3.3%), but a loss at the proximal tibia (-7.06%). There were no differences between groups or within groups over time. Significant negative correlations were found between baseline BMD and the amount of BMD change. CONCLUSION: Although not achieving statistical significance, hip BMD changes observed were greater than the reported 0.9-10% gains after exercise for children with and without disability. Thus, cycling with and without electrical stimulation may be beneficial for skeletal health in pediatric SCI, but further research is needed with a larger sample size.

Cycling for children with neuromuscular impairments using electrical stimulation--development of tricycle-based systems.

AIM: Cycling using functional electrical stimulation (FES-cycling) is a well defined exercise method for adults with spinal cord injury (SCI). Although little studied thus far, FES-cycling also has the potential to offer a means of exercise to pediatric populations, such as SCI or cerebral palsy (CP), that presently have few alternative options. The primary aim of this study was to develop FES-cycling equipment and methods which can meet the differing needs of children with SCI and CP. METHODS: Design criteria were determined based on key considerations for pediatric FES-cycling. Two separate prototype systems for training/recreation and laboratory-based research were built to meet these specifications. To experimentally verify the equipment, FES-cycling tests involving one child with motor complete SCI and one child with diplegic spastic CP were performed using the laboratory system. RESULTS: Experimental verification indicated that FES-cycling experiments involving children with SCI and CP are feasible provided that accurate measurement of both propulsive and resistive torque is achieved. Specific seating and orthotic needs for each subject population were met by both systems. CONCLUSION: The FES-cycling systems described here may assist in future investigations of pediatric FES-cycling performance and novel exercise regimes designed specifically for children.

Applications of cortical signals to neuroprosthetic control: a critical review.

Cortical signals might provide a potential means of interfacing with a neuroprosthesis. Guidelines regarding the necessary control features in terms of both performance characteristics and user requirements are presented, and their implications for the design of a first generation cortical control interface for a neuroprosthesis are discussed.

EEG-based control of a hand grasp neuroprosthesis.

The feasibility of using the EEG signal to operate a hand grasp neuroprosthesis was investigated. Two able-bodied subjects and one neuroprosthesis user were trained to control the amplitude of the beta rhythm recorded over the frontal areas. After 6 months, all subjects exhibited a high level of control, being able to use this signal to move a cursor to targets on a computer screen with a high (>90%) accuracy rate. Control over the EEG signal was unaffected by upper extremity movement or electrical activation of the muscles, indicating that this signal would be adequate for neuroprosthetic use. To test this concept, the neuroprosthesis user operated his system with the cortical signal, and was able to effectively manipulate several objects.

The function of the finger intrinsic muscles in response to electrical stimulation.

The actions of the dorsal interosseous, volar interosseous, and lumbrical muscles were investigated using applied electrical stimulation and recording the moments that were generated across the metacarpophalangeal joint in flexion/extension and abduction/adduction, the proximal interphalangeal joint in flexion/extension, and the distal interphalangeal joint in flexion/extension. These measurements were made isometrically at various joint angles and levels of stimulation with both able bodied subjects and persons who had sustained tetraplegia. It was determined that the dorsal interossei, including the first, were strong abductors of the fingers and generated a significant moment in metacarpophalangeal (MP) joint flexion and interphalangeal (IP) joint extension. The volar interossei were the primary adductors of the fingers, as well as providing a significant moment in MP joint flexion and IP joint extension. The lumbrical muscles were found to be MP joint flexors and IP joint extensors, although the moments that were generated were on average 70% lower than the interossei. The role of the lumbricals as finger abductors or adductors could not be determined from the data. This information on the actions and moment generating capabilities of the intrinsic muscles led to the incorporation of the interossei into electrically induced hand grasp provided by an implanted neuroprosthesis. The evaluation of the intrinsic muscles in the neuroprosthesis was accomplished by recording the moment generating capabilities of these muscles across each of the joints of the finger. These muscles were capable of generating moments that were 80-90% of the average attained by the able bodied subjects, and have provided a substantial improvement to the electrically induced hand grasp.

A transducer for the measurement of finger joint moments.

A device capable of simultaneously measuring the isometric moments generated about the metacarpophalangeal (MP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints of all four fingers has been developed. The design utilizes a four-bar linkage to transmit moments, but not forces, to the device. This linkage allows the same device to fit a wide range of hand sizes without recalibration. The device was constructed out of aluminum bars which are strapped to each joint segment and to the back of the hand. Strain gauges mounted to the aluminum bars measure the bending moment on the device, which is directly related to the moment applied about the joint center of rotation. Because of the unique design of the device, it is not necessary to have accurate measurements of the joint center of rotation in order to get accurate moment information. A single device is capable of generating independent measurement of MP extension/flexion, PIP extension/flexion, and DIP extension/flexion. Four of these devices can be used to make simultaneous measurements of all the moments generated by all four fingers. The device also acts as a splint, allowing each joint to be positioned and locked at any angle through the range of motion of the joint. The device is accurate to within +/- 5.6% of each reading for moments from 10 N x cm to 100 N x cm and within +/- 2.0 N x cm for moments of 10 N x cm or less. If the device configuration is constrained, the accuracy can be improved to +/- 0.8% of full scale (100 N x cm) and +/- 0.21 N x cm for moments of 10 N x cm or less. The device can measure both flexion and extension moments up to 100 N x cm, and can allow the joints to be fixed at any angle from approximately 10 to 80 degrees.