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Upper limb function is a high priority for people with cervical spinal cord injury (SCI). This case report describes an application of technology to activate spared neural pathways and improve wrist motor control. A 73-year-old man with chronic incomplete C5 SCI completed 24 training sessions over 92 days. Each session included 2 maximal contractions, 6 test trials, and 10 training trials of a visuomotor force tracking task. The participant attempted to match a sinusoidal target force curve, using isometric wrist flexor and extensor contractions. Electromyography (EMG) and force signals were recorded. Errors were elevated initially and improved with training, similarly during extension and flexion phases of the force tracking task. Improvement in both phases was associated with greater flexor activation in flexion phases and greater extensor relaxation in flexion phases. Errors were not related to EMG modulation during the extensor phases. Small improvements in active range of motion, grip force, spasticity, touch sensation, and corticospinal excitability were also observed. Motor skill training improved motor control after incomplete SCI, within the range of residual force production capacity. Performance gains were associated with specific adjustments in muscle activation and relaxation, and increased corticospinal excitability. [ABSTRACT FROM AUTHOR]

Abstract Background By quantifying the information entropy of postural sway data, the complexity of the postural movement of different populations can be assessed, giving insight into pathologic motor control functioning. Methods In this study, developmental delay of motor control function in infants was assessed by analysis of sitting postural sway data acquired from force plate center of pressure measurements. Two types of entropy measures were used: symbolic entropy, including a new asymmetric symbolic entropy measure, and approximate entropy, a more widely used entropy measure. For each method of analysis, parameters were adjusted to optimize the separation of the results from the infants with delayed development from infants with typical development. Results The method that gave the widest separation between the populations was the asymmetric symbolic entropy method, which we developed by modification of the symbolic entropy algorithm. The approximate entropy algorithm also performed well, using parameters optimized for the infant sitting data. The infants with delayed development were found to have less complex patterns of postural sway in the medial-lateral direction, and were found to have different left-right symmetry in their postural sway, as compared to typically developing infants. Conclusion The results of this study indicate that optimization of the entropy algorithm for infant sitting postural sway data can greatly improve the ability to separate the infants with developmental delay from typically developing infants.

In animal models, hundreds of repetitions of upper extremity (UE) task practice promote neural adaptation and functional gain. Recently, we demonstrated improved UE function following a similar intervention for people after stroke. In this secondary analysis, computerized measures of UE task performance were used to identify movement parameters that changed as function improved. Ten people with chronic poststroke hemiparesis participated in high-repetition UE task-specific training 3 times per week for 6 weeks. Before and after training, we assessed UE function with the Action Research Arm Test (ARAT), and evaluated motor performance using computerized motion capture during a reach-grasp-transport-release task. Movement parameters included the duration of each movement phase, trunk excursion, peak aperture, aperture path ratio, and peak grip force. Group results showed an improvement in ARAT scores (p = .003). Although each individual changed significantly on at least one movement parameter, across the group there were no changes in any movement parameter that reached or approached significance. Changes on the ARAT were not closely related to changes in movement parameters. Since aspects of motor performance that contribute to functional change vary across individuals, an individualized approach to upper extremity motion analysis appears warranted. [ABSTRACT FROM AUTHOR]

This study investigated whether grip type and/or task goal influenced reaching and grasping performance in poststroke hemiparesis. Sixteen adults with poststroke hemiparesis and twelve healthy adults reached to and grasped a cylindrical object using one of two grip types (3-finger or palmar) to achieve one of two task goals (hold or lift). Performance of the stroke group was characteristic of hemiparetic limb movement during reach-to-grasp, with more curved handpaths and slower velocities compared with the control group. These effects were present regardless of grip type or task goal. Other measures of reaching (reach time and reach velocity at object contact) and grasping (peak thumb-index finger aperture during the reach and peak grip force during the grasp) were differentially affected by grip type, task goal, or both, despite the presence of hemiparesis, providing new evidence that changes in motor patterns after stroke may occur to compensate for stroke-related motor impairment. [ABSTRACT FROM AUTHOR]

Background. Although slow and insufficient muscle activation is a hallmark of hemiparesis poststroke, movement speed is rarely emphasized during upper-extremity rehabilitation. Moving faster may increase the intensity of task-specific training, but positive and/or negative effects on paretic-limb movement quality are unknown. Objective. To determine whether moving quickly instead of at a preferred speed either enhances or impairs paretic-limb task performance after stroke. Methods. A total of 16 people with poststroke hemiparesis and 11 healthy controls performed reach–grasp–lift movements at their preferred speed and as fast as possible, using palmar and 3-finger grip types. The authors measured durations of the reach and grasp phases, straightness of the reach path, thumb–index finger separation (aperture), efficiency of finger movement, and grip force. Results. Reach and grasp phase durations decreased in the fast condition in both groups, showing that participants were able to move more quickly when asked. When moving fast, the hemiparetic group had reach durations equal to those of healthy controls moving at their preferred speed. Movement quality also improved. Reach paths were straighter, and peak apertures were greater in both groups in the fast condition. The group with hemiparesis also showed improved efficiency of finger movement. Differences in peak grip force across speed conditions did not reach significance. Conclusions. People with hemiparesis who can perform reach–grasp–lift movements with a 3-finger grip can move faster than they choose to, and when they do, movement quality improves. Simple instructions to move faster could be a cost-free and effective means of increasing rehabilitation intensity after stroke. [ABSTRACT FROM PUBLISHER]

The purpose of the present study was to compare the development of sitting postural control of typically developing infants with the sitting posture of healthy adults in terms of the center of pressure (COP) sway. Eight healthy adults and eight typically developing infants, at the point of developing the ability to sit upright, were recruited for this study. In order to mimic infant sitting, we had the adult subjects sit in a yoga style position directly on the force platform with their hands resting comfortably in their lap and head facing forward. The adult data collection lasted for 5 min and repeated three times. Each infant came to the lab twice per month for a period of 5 months, and three trials of sitting were recorded at each session. A physical therapist evaluated the infant's sitting behavior and ranked the stage of sitting at each session. The stages were 1) prop sitting; 2) variable, about 10 s of sitting; and 3) sits upright all the time--doesn't need hands. Each trial consisted of recording COP data for 8.3 s of unsupported sitting on a force plate. The COP data were analyzed using the root mean square (RMS) measure, which is a linear method of quantifying amount of sway for both the sagittal and frontal planes of motion. The statistical analysis consisted of independent t test between each stage of infant sitting and adult sitting. The results showed that Stages 2 and 3 of infant sitting had significantly higher RMS values than the adult sitting behavior in the sagittal plane of motion. Regarding the frontal plane of motion, all stages of infant sitting behavior had significantly smaller RMS values than adult sitting. These results suggest that during the development of sitting infants tend to freeze the degrees of freedom of motion to be more stable in the frontal plane of motion while they are more explorative in the sagittal plane of motion. As development continues frontal plane stability may be of higher importance as other skills (i.e., standing, walking) come into play. [ABSTRACT FROM AUTHOR]

Early identification of infants with developmental delay will allow access to therapeutic intervention earlier in development, possibly resulting in better outcomes. Sitting is one of the first developmental motor milestones an infant achieves, and thus sitting postural control provides an early window into the developing motor control system. Infants (n = 17) were recruited when they were just developing the ability to sit upright. Each came to the laboratory twice per month for a period of 4 months, and typically three trials were recorded at each session. Each trial consisted of recording COP data at 240 Hz for 8.3 s of unsupported sitting on an AMTI force plate. A total number of 116 trials were included in this study for each of three groups, typically developing (n = 5), mild delay (n = 6), and severe delay (n = 6). Severity scores were determined by a trained physical therapist, and then the data were grouped based on the score. Variability present in the COP data was analyzed using sway path, a linear measure, and the largest Lyapunov exponent (LyE), a nonlinear measure. The groups were compared using independent t tests with a Bonferroni correction for multiple comparisons. The analysis showed that sway path decreased with severity. Lyapunov exponent decreased with severity, but only in the mediolateral direction. The sway path is a measure of the length of the line that is transversed by the COP during data acquisition, and the more severely affected infants were found to have less movement of the COP during sitting. A larger positive LyE is often taken as indicative of a more chaotic system. Thus the lower LyE associated with more severely affected infants indicates less complexity in their movement. Infants with developmental delay not only have less postural sway, but also the quality of their movement is found to be less complex. This is consistent with the theory of optimal movement variability in human motor control. This work was supported by the NIH (K25HD047194), the NIDRR (H133G040118), and the Nebraska Research Initiative. [ABSTRACT FROM AUTHOR]