Background/Study Context: The study was a longitudinal assessment of age-related changes in standing balance and response strategy usage in healthy adults.
Methods: Balance of 17 individuals with a ...mean age of 44.5 years was assessed and then reassessed 19.5 years later. Participants stood on computer-controlled dual-force platforms enclosed by a visual surround and completed six tests in which visual and/or somatosensory information was systematically degraded or eliminated.
Results: Results for each test and a weighted composite balance score revealed no significant change in postural control over the time period studied. However, response strategy scores indicated some significant change with age. Specifically, compensatory movement corrections about the ankle complex increased when standing on a stable support surface with and without vision, and hip-centered corrections were prominent when standing on an unstable surface with eyes open or closed.
Conclusion: Increased reliance on response strategy usage with time is interpreted as a compensatory adjustment to age-related increases in postural instability and accounts for the absence of any change in standing balance under different conditions of sensory input.
Background
Impaired motor function in children with histories of prenatal exposure to alcohol has been previously reported but, to date, no studies using quantitatively based analyses have been ...performed to assess gait in these children.
Methods
Gait of children with (n = 18) or without (n = 26) prenatal alcohol exposure was assessed using an electronically instrumented walkway. Children completed blocks of trials traversing the walkway with different combinations of walking condition (increased, self‐paced, and decreased cadence) and direction (forward and backward). Gait velocity, cadence, stride length, step width, foot angle, and double support time, as well as the variability of these temporal–spatial markers, were used to assess gait.
Results
Results indicated that, in comparison with typically developing children, alcohol‐exposed children produced exaggerated foot angle and increased step width. Additionally, alcohol‐exposed children produced greater intrasubject variability of gait velocity and walking cadence while walking forward and backward, and greater variability in step width when walking backward and for all 3 walking conditions.
Conclusions
The results indicate that selected gait markers are adversely affected by prenatal exposure to alcohol. Clinicians and front‐line personnel (e.g., teachers) should provide movement enriched experiences to help ameliorate these alcohol‐related deficits.
The current profile of gait control in children with ADHD is incomplete and predominately based on children walking forward at a self-selected pace. There are no studies of potential gait deficits in ...this clinical population when walking in different directions in combination with varying rates of stepping that are freely selected and entrained to an external stimulus. The purpose of the current study was to address this lack of information by assessing gait of children aged 7–17 years with (n = 17) and without (n = 26) ADHD. Participants walked forward and backward along an electronically instrumented carpet at a self-selected stepping rate and in synchrony to a metronome that dictated an increased and decreased stepping rate. Using repeated measures analysis of covariance (ANCOVA) to assess spatiotemporal gait parameters, results showed that children with ADHD exhibited a significantly exaggerated, toes ‘turned out,’ foot position for all walking conditions compared to typically developing children. When walking backward, children with ADHD produced an increased step width, higher stepping cadence, and increased velocity. Additionally, coefficient of variation ratios indicated that children with ADHD produced greater variability of velocity, cadence, and step time for all walking conditions, and greater variability for stride length when walking at an increased stepping rate. Results were interpreted in terms of clinical significance and practical ramifications that inform rehabilitation specialists in designing therapies that ameliorate the reported gait deficits.
Segmental kinematics were investigated in horses during overground locomotion and compared with published reports on humans and other primates to determine the impact of a large neck on rotational ...mobility (> 20 deg.) and stability (< or = 20 deg.) of the head and trunk. Three adult horses (Equus caballus) performing walks, trots and canters were videotaped in lateral view. Data analysis included locomotor velocity, segmental positions, pitch and linear displacements and velocities, and head displacement frequencies. Equine, human and monkey skulls and cervical spines were measured to estimate eye and vestibular arc length during head pitch displacements. Horses stabilized all three segments in all planes during all three gaits, unlike monkeys and humans who make large head pitch and yaw rotations during walks, and monkeys that make large trunk pitch rotations during gallops. Equine head angular displacements and velocities, with some exceptions during walks, were smaller than in humans and other primates. Nevertheless, owing to greater off-axis distances, orbital and vestibular arc lengths remained larger in horses, with the exception of head-neck axial pitch during trots, in which equine arc lengths were smaller than in running humans. Unlike monkeys and humans, equine head peak-frequency ranges fell within the estimated range in which inertia has a compensatory stabilizing effect. This inertial effect was typically over-ridden, however, by muscular or ligamentous intervention. Thus, equine head pitch was not consistently compensatory, as reported in humans. The equine neck isolated the head from the trunk enabling both segments to provide a spatial reference frame.
Evidence from small-scale studies indicates that impairments in postural stability are an early and disabling feature of Huntington's disease (HD) and may be a useful clinical endpoint for disease ...modifying trials. Larger studies are needed to confirm these preliminary findings and the suitability of postural stability outcomes as clinical endpoints. Static and dynamic postural stability were evaluated in 54 premanifest HD, 36 manifest HD and 45 healthy individuals using the Sensory Organization Test (SOT) and Limits of Stability (LOS) test. Manifest HD displayed significantly lower scores on all SOT conditions and on the SOT composite score and had more falls than healthy and premanifest HD (p < 0.05). Premanifest and manifest HD demonstrated significantly lower endpoint excursion (p < 0.001), maximum excursion (p ≤ 0.001), and directional control (p ≤ 0.004) values than healthy individuals on the LOS test. Deficits in LOS were found to manifest on the left side of premanifest HD. Significant but low associations were observed between UHDRS-TMS, disease burden score, diagnostic confidence level, SOT conditions and SOT composite score. We confirm here that individuals with premanifest and manifest HD display significant impairments in static and dynamic postural stability. Dynamic posturography assessments should be considered as clinical endpoints for future disease modifying trials.
Aims
Empirical investigations reveal that, in comparison to their typically developing peers, children with histories of prenatal alcohol exposure experience deficits in writing but not drawing ...skills, both of which require fine motor control. This study examines drawing skills in this clinical group by assessing simple free‐form spiral drawings with indices of spectral features and structural organization.
Methods
Children with (n = 15) and without (n = 24) prenatal alcohol exposure used their dominant and nondominant hands to draw a series of spirals using a wireless pen stylus that either provided concurrent visual feedback in the form of a black ink trace or left no visible ink trace of each drawing. Spirals were drawn on a sheet of paper placed on a digitizing table, which facilitated online data acquisition. The data were assessed by power spectral density function analysis and sample entropy analysis.
Results
In comparison to their typically developing peers, children with prenatal alcohol exposure produced spirals with a lower mean frequency and less spectral variability. Spirals in the prenatally exposed group were also lower in complexity and structural organization than in the control group. These results occurred independently of hand dominance or the availability of visual feedback.
Conclusions
The drawing skills of children with prenatal alcohol exposure have inherent signal characteristics that differ significantly from those produced by typically developing peers. Simple tasks requiring fine motor control may be useful in identifying individuals with fetal alcohol spectrum disorders.
Children with prenatal alcohol exposure and typically developing children were required to draw a series of free‐form Archimedes spirals with and without visual feedback using the dominant and non‐dominant hands. Power spectral density analysis and estimates of sample entropy revealed that children with histories of gestational alcohol exposure produced atypical spirals characterized by different frequency characteristics and low structural regularity. The observed deficits in spiral drawing performance align with previous reports of impaired motor control in this clinical group.
Background
Many daily functional activities involve goal‐directed responses based on open‐loop and closed‐loop motor control, yet little is known about how children with heavy prenatal alcohol ...exposure organize and regulate these 2 types of control systems when completing a goal‐directed force response.
Methods
Children with (n = 19) or without (n = 23) heavy prenatal alcohol exposure were required to match a target force (25 and 50% of maximum voluntary force) in a specified target time (200, 800, and 2,000 ms). Target force and produced force were visually displayed on a computer monitor. The analog force–time record was parsed into 2 segments: the period beginning from force initiation to the first reversal in force was designated the open‐loop phase, and the remainder of the response was the closed‐loop phase.
Results
Compared to controls, alcohol‐exposed children produced a significantly shorter duration of open‐loop control, a higher open‐loop phase rate of force development, a shorter time to reach maximum force during the closed‐loop phase, and greater absolute target force error. Increasing target force magnitude did not differentially alter the performance of the clinical group.
Conclusions
The results indicate that alcohol‐exposed children experience deficits in completing goal‐directed force responses that likely stem from an alcohol‐related insult to the central nervous system. Therapeutic exercises should be designed to recalibrate internal timing systems and improve visuomotor integration.
Trained ballet dancers and nondancer controls completed six balance tests using computerized dynamic posturography. The tests facilitated assessment of the type of sensory organization used to ...maintain postural control under conditions ranging from quiet standing to a situation in which visual and/or somatosensory information was systematically removed or made unreliable. Results indicated that ballet dancers and controls have comparable balance ability during eyes open and eyes closed conditions. However, when somatosensory information alone or in combination with visual information was made unreliable, dancers were significantly less stable than controls and utilized a hip strategy to maintain postural control.
Background: Production of isometric (i.e., constant) force is an essential component of performing everyday functional tasks, yet no studies have investigated how this type of force is regulated in ...children with confirmed histories of heavy prenatal alcohol exposure.
Methods: Children 7 to 17 years old with heavy prenatal alcohol exposure (n = 25) and without exposure (n = 18) applied force to a load cell to generate an isometric force that matched a criterion target force displayed on a computer monitor. Two levels of target force were investigated in combination with 3 levels of visual feedback frequency that appeared on the computer monitor as a series of yellow dots. Force was maintained for 20 seconds and participants completed 6 trials per test condition.
Results: Root‐mean‐square error, signal‐to‐noise ratio, and sample entropy indexed response accuracy, response variability, and signal complexity, respectively. The analyses revealed that in comparison with controls, children with gestational ethanol exposure were significantly less accurate and more variable in regulating their force output and generated a response signal with greater regularity and less complexity in the time domain.
Conclusions: Children with prenatal alcohol exposure experience significant deficits in isometric force production that may impede their ability to perform basic motor skills and activities in everyday tasks.
The balance of trained ballet dancers and non-dancer controls was mechanically perturbed in order to evaluate the time of onset of muscle activation and the consistency of muscle activation. Results ...supported the prediction that ballet dancers have significantly faster long-latency (LL) neuromuscular responses than controls and are significantly more consistent in muscle activation. These findings indicate a superior postural control mechanism in trained dancers and may explain the ability of dancers to maintain static balances over a small base of support.
PDF
