The effect of Tai Chi lower extremity exercise on the balance control of older adults in assistant living communities.

BACKGROUND: Although Tai Chi (TC) is an evidence-based fall prevention training for older adults, its effective movements remain unclear, which may limit the practice of TC. The purpose of this study was to compare the effectiveness of TC lower extremity exercise (TC LEE), the 8-form Tai Chi (8-form TC), and a stretching control intervention for improving balance and functional mobility among older adults. METHODS: This was a randomized controlled trial. A total of 102 participants (79 ± 6 years old) were recruited from assisted living facilities. All participants were randomly assigned to the TC LEE (n = 40), 8-form TC (n = 31), and stretching (n = 31) groups in which they received the respective interventions for 16 weeks. The Berg Balance Scale (BBS), Timed Up and Go (TUG) test, and center of pressure (COP) measurements during quiet stance were collected prior to and following the 16-week interventions. Comparisons on all measurements were conducted among all groups. RESULTS: Significant improvements were found in BBS (P = 0.002), TUG test (P = 0.001), root mean square amplitude of COP displacement in the anterior-posterior (P = 0.001) and medial-lateral (P = 0.001) directions, and average COP speed in the anterior-posterior (P = 0.001) and medial-lateral (P = 0.001) directions after training in the TC intervention groups compared with the stretching group. The upper limit of the 95% confidence interval (CI) of differences in change scores on the BBS (-0.8 - 1.3 points) between the TC LEE group and the 8-form TC group was within equivalence margins (1.8 points), while the upper limit of the 95% CI of differences in change scores on the TUG test (0.1 - 2.1 s) exceeded the equivalence margin (0.7 s) with the TC LEE group having the larger change scores. CONCLUSION: TC LEE can improve balance and functional mobility in older adults, and may have greater effect than the 8-form TC on improving functional mobility as measured by the TUG test. TRIAL REGISTRATION: ChiCTR2300070600 retrospectively registered.

Does the effect of walking balance perturbations generalize across contexts?

Balance perturbations are used to study locomotor instability. However, these perturbations are designed to provoke a specific context of instability that may or may not generalize to a broader understanding of falls risk. The purpose of this study was to determine if the effect of balance perturbations on instability generalizes across contexts. 29 younger adults and 28 older adults completed four experimental trials, including unperturbed walking and walking while responding to three perturbation contexts: mediolateral optical flow, treadmill-induced slips, and lateral waist-pulls. We quantified the effect of perturbations as an absolute change in margin of stability from unperturbed walking. We found significant changes in mediolateral and anteroposterior margin of stability for all perturbations compared to unperturbed walking in both cohorts (p-values ≤ 0.042). In older adults, the mediolateral effects of lateral waist-pulls significantly correlated with those of optical flow perturbations and treadmill-induced slips (r ≥ 0.398, p-values ≤ 0.036). In younger adults but not in older adults, we found positive and significant correlations between the anteroposterior effect of waist-pull perturbations and optical flow perturbations, and the anteroposterior and mediolateral effect of treadmill-induced slips (r ≥ 0.428, p-values ≤ 0.021). We found no "goldilocks" perturbation paradigm to endorse that would support universal interpretations about locomotor instability. Building the most accurate patient profiles of instability likely requires a series of perturbation paradigms designed to emulate the variety of environmental contexts in which falls may occur.

Susceptibility to walking balance perturbations in young adults is largely unaffected by anticipation.

Despite progress in understanding the mechanisms governing walking balance control, the number of falls in our older adult population is projected to increase. Falls prevention systems and strategies may benefit from understanding how anticipation of a balance perturbation affects the planning and execution of biomechanical responses to mitigate instability. However, the extent to which anticipation affects the proactive and reactive adjustments to perturbations has yet to be fully investigated, even in young adults. Our purpose was to investigate the effects of anticipation on susceptibility to two different mechanical balance perturbations - namely, treadmill-induced perturbations and impulsive waist-pull perturbations. Twenty young adults (mean ± standard deviation age: 22.8 ± 3.3 years) walked on a treadmill without perturbations and while responding to treadmill belt (200 ms, 6 m/s2) and waist-pull (100 ms, 6% body weight) perturbations delivered in the anterior and posterior directions. We used 3D motion capture to calculate susceptibility to perturbations during the perturbed and preceding strides via whole-body angular momentum (WBAM) and anterior-posterior margin of stability (MoSAP). Contrary to our hypotheses, anticipation did not affect young adults' susceptibility to walking balance challenges. Conversely, perturbation direction significantly affected walking instability. We also found that susceptibility to different perturbation contexts is dependent on the outcome measure chosen. We suggest that the absence of an effect of anticipation on susceptibility to walking balance perturbations in healthy young adults is a consequence of their having high confidence in their reactive balance integrity. These data provide a pivotal benchmark for the future identification of how anticipation of a balance challenge affects proactive and reactive balance control in populations at risk of falls.

Brief composite mobility index predicts post-stroke fallers after hospital discharge.

Introduction: Community-dwelling, ambulatory stroke survivors fall at very high rates in the first 3-6 months. Current inpatient clinical assessments for fall risk have inadequate predictive accuracy. We found that a pre-discharge obstacle-crossing test has excellent specificity (83%) but lacks acceptable sensitivity (67%) for identifying would-be fallers and non-fallers post discharge. Hypothesis: We assessed the hypothesis that combining the obstacle-crossing test with other highly discriminatory fall risk factors would compensate for the obstacle test's fair sensitivity and yield an instrument with superior prediction accuracy. Methods: 45 ambulatory stroke survivors (60 ± 11 years old, 15 ± 11 days post stroke) being discharged home completed a battery of physical performance-based and self-reported measures 1-5 days prior to discharge. After discharge, participants were prospectively followed and classified as fallers (≥1 fall) or non-fallers at 3 months. Pre-discharge measures with the largest effect sizes for differentiating fallers and non-fallers were combined into a composite index. Several variations of the composite index were examined to optimize accuracy. Results: A 4-item discharge composite index significantly predicted fall status at 3-months. The goodness of fit of the regression model was significantly better than the obstacle-crossing test alone, χ 2(1) = 6.036, p = 0.014. Furthermore, whereas the obstacle-crossing test had acceptable overall accuracy (AUC 0.78, 95% CI, 0.60-0.90), the composite index had excellent accuracy (AUC 0.85, 95% CI, 0.74-0.96). Combining the obstacle-crossing test with only the step test produced a model of equivalent accuracy (AUC 0.85, 95% CI, 0.73-0.96) and with better symmetry between sensitivity and specificity (0.71, 0.83) than the 4-item composite index (0.86, 0.67). This 2-item index was validated in an independent sample of n = 30 and with bootstrapping 1,000 samples from the pooled cohorts. The 4-item index was internally validated with bootstrapping 1,000 samples from the derivation cohort plus n = 9 additional participants. Conclusion: This study provides convincing proof-of-concept that strategic aggregation of performance-based and self-reported mobility measures, including a novel and demanding obstacle-crossing test, can predict post-discharge fallers with excellent accuracy. Further instrument development is warranted to construct a brief aggregate tool that will be pragmatic for inpatient use and improve identification of future post-stroke fallers before the first fall.

Slowing down to preserve balance in the presence of optical flow perturbations.

BACKGROUND: The use of sensory and mechanical perturbations applied during walking has grown in popularity due to their ability to elicit instability relevant to falls. However, the vast majority of perturbation studies on walking balance are performed on a treadmill at a fixed speed. RESEARCH QUESTION: The aim of this study was to quantify the effects of mediolateral optical flow perturbations on walking speed and balance outcomes in young adults walking with fixed-speed and self-paced treadmill controllers. METHODS: Fifteen healthy young adults (8 female, age: 23.1 ± 4.6 yrs) completed four five-minute randomized walking trials in a speed-matched virtual reality hallway. In two of the trials, we added continuous mediolateral optical flow perturbations to the virtual hallway. Trials with and without optical flow perturbations were performed with either a fixed-speed or self-paced treadmill controller. We measured walking speed, balance outcomes (step width, margin of stability, local dynamic instability) and gait variability (step width variability and margin of stability variability). RESULTS: We found significant increases in step width (+20%, p = 0.004) and local dynamic instability (+11%, p = 0.008) of participants while responding to optical flow perturbations at a fixed treadmill speed. We found no significant differences in these outcome measures when perturbations were applied on a self-paced treadmill. Instead, participants walked 5.7% slower between the self-paced treadmill controller conditions when responding to optical flow perturbations (1.48 ± 0.13 m/s vs. 1.57 ± 0.16 m/s, p = 0.005). SIGNIFICANCE: Our findings suggest that during walking, when presented with a balance challenge, an individual will instinctively reduce their walking speed in order to better preserve stability. However, comparisons to prior literature suggest that this response may depend on environmental and/or perturbation context. Cumulatively, our results point to opportunities for leveraging self-paced treadmill controllers as a more ecologically-relevant option in balance research with potential clinical applications in diagnostics and rehabilitation.

Utility of an obstacle-crossing test to classify future fallers and non-fallers at hospital discharge after stroke: A pilot study.

BACKGROUND: Existing clinical assessments of balance and functional mobility have poor predictive accuracy for prospectively identifying post-stroke fallers, which may be due to a lack of ecological complexity that is typical of community-based fall incidents. RESEARCH QUESTION: Does an obstacle-crossing test at hospital discharge predict fall status of ambulatory stroke survivors 3 months after discharge? METHODS: Ambulatory stroke survivors being discharged home completed an obstacle-crossing test at hospital discharge. Falls were tracked prospectively for 3 months after discharge. Logistic regression examined the relationship between obstacle-crossing at discharge (pass/fail) and fall status (faller/non-faller) at 3 months post discharge. RESULTS: 45 participants had discharge obstacle test and 3-month fall data. 21 (47 %) participants experienced at least one fall during follow-up, with 52 % of the falls occurring within the first month after discharge. Of the 21 fallers, 14 failed the obstacle-crossing test (67 % sensitivity). Among the 24 non-fallers, 20 passed the obstacle-crossing test (83 % specificity). The area under the receiver operating characteristic curve was 0.75 (95 % CI 0.60-0.90). Individuals who failed the obstacle-crossing test were 10.00 (95 % CI: 2.45-40.78) times more likely to fall in the first 3 months after discharge. The unadjusted logistic regression model correctly classified 76 % of the subjects. After adjusting for age, sex, days post stroke, and post-stroke disability, the odds ratio remained significant at 6.93 (95 % CI: 1.01-47.52) and correctly classified 79.5% of the participants. SIGNIFICANCE: The obstacle-crossing test may be a useful discharge assessment to identify ambulatory stroke survivors being discharged home who are likely to fall in the first 3 months post discharge. Modifications to improve the obstacle-crossing test sensitivity should be explored further.

Effects of the Matter of Balance Program on Self-Reported Physical Activity in Community-Dwelling Older Adults.

Objective: To (a) evaluate effects of the Matter of Balance (MOB) program on self-reported physical activity (PA) in older adults as measured by the program's activity (MOB-PA) measure and the Rapid Assessment of Physical Activity, Part 1 (RAPA1) and (b) for a separate Community cohort, explore correlations between MOB-PA and RAPA1 scores and step counts obtained using accelerometry. Methods: Community-dwelling older adults recruited from upcoming MOB classes and from in-person contacts comprised MOB (N = 56) and Community (N = 23) cohorts, respectively. For the MOB cohort, paired t tests were computed for baseline and follow-up MOB-PA and RAPA1 scores. For the Community cohort, Pearson's correlations between self-reported PA and step counter measures were calculated. Results: Self-reported PA did not change following MOB participation. The MOB-PA had substantial ceiling effects, which weakened relationships with step counter data. Discussion: No evidence was found that MOB participation increased PA. The MOB-PA may not be appropriate for measuring activity levels.

Lower-extremity osteoarthritis and the risk of falls in a community-based longitudinal study of adults with and without osteoarthritis.

OBJECTIVE: Knee and hip osteoarthritis (OA) are known risk factors for falls, but whether they together additionally contribute to falls risk is unknown. This study utilizes a biracial cohort of men and women to examine the influence of lower-extremity OA burden on the risk for future falls. METHODS: A longitudinal analysis was performed using data from 2 time points of a large cohort. The outcome of interest was falls at followup. Covariates included age, sex, race, body mass index, a history of prior falls, symptomatic OA of the hip and/or knee, a history of neurologic or pulmonary diseases, and current use of narcotic medications. Symptomatic OA was defined as patient-reported symptoms and radiographic evidence of OA in the same joint. Logistic regression analyses were used to determine associations between covariates and falls at followup. RESULTS: The odds of falling increased with an increasing number of lower-extremity symptomatic OA joints: those with 1 joint had 53% higher odds, those with 2 joints had 74% higher odds, and those with 3-4 OA joints had 85% higher odds. When controlling for covariates, patients who had symptomatic knee or hip OA had an increased likelihood of falling (adjusted odds ratio [aOR] 1.39, 95% confidence interval [95% CI] 1.02-1.88 and aOR 1.60, 95% CI 1.14-2.24, respectively). CONCLUSION: This study reveals the risk for falls increases with additional symptomatic OA lower-extremity joints and confirms that symptomatic hip and knee OA are important risk factors for falls.

Association of self-efficacy and outcome expectations with physical activity in adults with arthritis.

Background and Purpose. The purpose of this study is to determine whether higher baseline levels of (a) self-efficacy for physical activity, (b) self-efficacy for arthritis self-management, and (c) outcome expectations for exercise are associated with higher physical activity levels following an exercise intervention for adults with arthritis. Methods. A secondary analysis of the intervention cohort (n = 130) within a randomized controlled trial of the People with Arthritis Can Exercise program was performed. Multiple linear regression evaluated the relationship between physical activity at a time point three months after the completion of an exercise intervention and three main explanatory variables. Results. After controlling for baseline physical activity, neither self-efficacy for arthritis self-management nor outcome expectations for exercise related to three-month physical activity levels. There was a relationship between three-month physical activity and self-efficacy for physical activity. Conclusions. Future research is needed to evaluate the ability of self-efficacy-enhancing programs to increase physical activity in adults with arthritis.

Influence of lower extremity sensory function on locomotor adaptation following stroke: a review.

Following stroke, people commonly demonstrate locomotor impairments including reduced walking speed and spatiotemporal asymmetry. Rehabilitation programs have been effective in increasing gait speed, but spatiotemporal asymmetry has been more resistant to change. The inability to modify gait patterns for improved symmetry may be related, in part, to impairments in lower extremity sensation. Assessment of lower extremity sensory impairments in people post stroke, including cutaneous and proprioceptive sensation, has been insufficiently studied. Conventional rehabilitation programs, including body weight-supported walking or robotic assistance, that modify sensory feedback intended to alter lower extremity movement patterns have shown limited success in improving gait symmetry. Rehabilitation programs that amplify specific gait asymmetries have demonstrated the potential to ultimately produce more symmetric gait, presumably by allowing individuals post stroke to more readily perceive their gait asymmetry. The effectiveness of such error augmentation paradigms, however, may be influenced by lower extremity sensation and the ability of the central nervous system to be aware of altered lower extremity movement. The purpose of this review is to critically examine the literature on lower extremity sensory function and its influence on gait adaptation in people post stroke.

The relationships between technique variability and performance in discus throwing.

Discus throwing performance is associated with technique variables. However, the relationships between technique variability and performance in discus throwing are unknown. Video clips of three throws each by 18 male and 15 female discus throwers were collected during a competition. Two-dimensional coordinate data were manually digitised and transferred into three-dimensional coordinates of body landmarks. Eight joint angles were calculated and their values were time-normalised to 101 frames from the initiation to the end of a throw. The mean standard deviations of 101 frames for eight joint angles among the three throws were calculated as the variability measurement. The best official distance of three throws was used as the performance measurement. For male throwers, the canonical correlations between technique variability and performance were significant (P < 0.1). Pearson correlations showed that the performance was significantly negatively correlated with the mean standard deviations of arm-shoulder separation angle (r = -0.57, P = 0.02), hip-shoulder separation angle (r = -0.63, P < 0.01), left hip flexion angle (r = -0.5, P = 0.03), and trunk forward-backward tilt angle (r = -0.57, P = 0.02). For female throwers, the canonical correlations between technique variability and performance were not significant (P > 0.1). Male discus throwers with a longer throwing distance had smaller variability in reproducing techniques. Reducing motion variability may be an important goal for discus training in males.

Effects of foot orthoses on balance in older adults.

STUDY DESIGN: Controlled laboratory study using a single-cohort design. OBJECTIVES: To determine if balance in older adults could be significantly improved with foot-orthotic intervention. BACKGROUND: Poor balance has been associated with risk for falls. Limited evidence exists indicating that foot orthoses influence balance. METHODS: Thirteen individuals older than 65 years, who reported at least 1 unexplained fall during the past year and demonstrated poor balance, participated in the study. Subjects were tested for 1-leg stance, tandem stance, tandem gait, and alternating step tests during the first (SCREEN) and second (PRE) sessions prior to foot-orthotic intervention. Tests were repeated during the second testing session immediately after custom foot-orthotic intervention (POST) and 2 weeks following foot-orthotic use (FU). SCREEN and PRE measures were compared for stability using absolute difference computations and the Friedman rank test. PRE, POST, and FU data were analyzed using the Friedman rank test (α = .05), with Bonferroni correction for multiple post hoc comparisons. RESULTS: Each balance measure was statistically equivalent between the SCREEN and PRE measurements. One-leg stance times for PRE were significantly less than POST (P = .002) and FU (P = .013) measurements. Tandem stance times for PRE were significantly less than POST (P = .013) and FU (P = .013) measurements. Steps taken for the tandem gait test during the PRE measurements were significantly fewer than steps taken for the FU test (P = .007). Steps taken during the alternating step test for the PRE test were significantly fewer than steps taken during the POST (P = .002) and FU (P =.001) tests. POST and FU measurements were not significantly different for any of the 4 outcome measures. CONCLUSIONS: The results provide preliminary evidence that foot orthoses can effect improvement in balance measures for older adults.

The necessity for effective interaction between basic scientists and rehabilitation clinicians.

Important basic science research is being conducted that has direct implications for the rehabilitation of patients, but the translation of this research to change clinical practice does not occur automatically. Advisory panels to the National Center for Medical Rehabilitation Research acknowledge a need for basic and applied research related to the factors underlying coordinated movements, such as the interactions of the neuromuscular and musculoskeletal systems. In this paper, we briefly describe recent studies that have examined the preceding interaction and discuss some basic issues related to the translation of these experiments to the clinic. More importantly, the main purpose of this paper is to discuss models/ways to translate basic science to clinical practice in a two-way and informed interaction between basic scientists and clinicians.

Responses to a modified visual cliff by pre-walking infants born preterm and at term.

The purpose of this study was to examine, using a modified visual cliff apparatus, possible perceptual differences at crawling age between infants born preterm and infants born at term without documented visual or motor impairments. Sixteen infants born at term and 16 born preterm were encouraged to crawl to their caregivers on a modified visual cliff. Successful trials, crossing time, duration of visual attention, duration of tactile exploration, motor strategies, and avoidance behaviors were analyzed. A significant surface effect was found, with longer crossing times and longer durations of visual attention and tactile exploration in the condition with the visual appearance of a deep cliff. Although the two groups of infants did not differ on any of the timed measures, infants born at term demonstrated a larger number of motor strategies and avoidance behaviors by simple tally. This study indicates that infants born at term and those born preterm can perceive a visual cliff and adapt their responses accordingly.

Effects of an exercise program to increase hip abductor muscle strength and improve lateral stability following stroke: a single subject design.

BACKGROUND AND PURPOSE: Persons with lower extremity weakness following stroke often demonstrate difficulty with weight transfer and paretic lower extremity loading. These deficits, in turn, can lead to problems with lateral stability, or the ability to control movement of the center of mass in the frontal plane. The primary aim of this study was to examine the efficacy of an individualized home exercise program in improving hip abductor muscle strength and lateral stability in a subject with chronic stroke. METHODS: An A-B-A treatment-withdrawal single-subject design was used. The subject was a 70-year-old male who had experienced a left hemispheric stroke 36 months prior to initiation of the study. Bilateral hip abductor muscle strength, single limb stance (SLS), timed 360 degrees turn, Step Test, and 10-m walk at self-selected and fast speeds were recorded at regular intervals during the baseline (A-I), treatment (B), and treatment-withdrawal (A-2) phases. The home exercise program in the B phase consisted of lower extremity weight bearing and weight transfer activities and exercise on a lateral training device 3 to 5 times a week for 6 weeks. The Berg Balance Scale (BBS) and Stroke Impact Scale (SIS) were administered at the completion of each phase and at 6-week follow-up. Data were analyzed using visual analysis and the split-middle method of trend estimation. RESULTS: Mean levels of all measures improved from A-1 to B phases, with significant increases in trend for hip abductor muscle strength and SLS bilaterally. Most improvements were maintained during the treatment-withdrawal (A-2) phase and at follow-up. CONCLUSION: A home exercise program that includes exercise on a lateral training device shows promise for producing increases in hip abductor muscle strength and accompanying improvements in some measures of physical performance and disability in persons with chronic stroke.

Infants born preterm exhibit different patterns of center-of-pressure movement than infants born at full term.

BACKGROUND: Infants born preterm are at risk for developmental impairments related to postural control. OBJECTIVE: The purpose of this study was to determine whether infants born preterm and infants born at full term differed in postural control at 1 to 3 weeks after term age. DESIGN: This study included 17 infants born preterm (mean gestational age=31.9 weeks, range=25.0-34.6) and 15 infants born at full term (mean gestational age=38.9 weeks, range=37.3-40.6). All infants were without diagnosed neurological or genetic conditions. MEASUREMENT: Center-of-pressure (COP) data were recorded at 5 Hz while each infant was positioned supine on a pressure-sensitive mat in an alert behavioral state. Root mean square (RMS) displacement and approximate entropy (ApEn) were used to describe the COP movement variability in the time series. Differences between groups were identified using independent t tests. RESULTS: The COP time series were found to be deterministic, suggesting order in the time series. Infants born preterm exhibited significantly larger RMS values in the caudal-cephalic direction than infants born at full term (1.11 and 0.83 cm, respectively; t=-2.6, df=30, P=.01). However, infants born at full term had significantly larger ApEn values in the caudal-cephalic direction (1.19 and 1.11, respectively; t=2.4, df=30, P=.02). The 2 groups did not differ in RMS or ApEn values in the medial-lateral direction or the resultant. CONCLUSIONS: Infants born at full term exhibited COP displacements in the caudal-cephalic direction that were smaller in amplitude, but may be considered more complex or less predictable, than those of infants born preterm. One explanation is that infants born preterm exhibited more stereotypic patterns of movement, resulting in large, but repetitive, COP excursions. A combination of linear and nonlinear measures may provide insight into the control of posture of young infants.

A pilot study: coordination of precision grip in children and adolescents with high functioning autism.

PURPOSE: This pilot study compared temporal coordination during a precision grip task between 13 children and adolescents with autism spectrum disorders (ASD) who were high functioning and 13 peers with typical development. METHODS: Temporal coordination between grip and load forces was measured using latency between onset of grip and load forces, grip force at onset of load force, peak grip force (PGF), and time to PGF. RESULTS: Compared with peers with typical development, participants with ASD demonstrated prolonged latency between grip and load forces, elevated grip force at onset of load force, and increased movement variability. PGF and time to PGF were not significantly different between the 2 groups. CONCLUSIONS: These findings indicate temporal dyscoordination in participants with ASD. The findings also enhance our understanding of motor coordination deficits in persons with ASD and have theoretical as well as clinical implications.

Reliability and validity of a clinical test of reaction time in older adults.

PURPOSE: Reaction time is an important indicator of neuromuscular status in older adults. A simple, portable, and inexpensive method of measuring reaction time is needed for use in geriatric clinical settings. The purpose of this study was to examine the reliability and validity of the response speed subtest of the Bruininks-Oseretsky Test of Motor Proficiency (BOT) as an indicator of reaction time in older adults. METHODS: A volunteer sample of 30 community-dwelling men and women over the age of 65 years performed the response speed subtest of the BOT and an electronic reaction time test during a single test session. Statistical analyses included calculation of the intraclass correlation coefficient (ICC) for reliability testing and the Pearson product-moment correlation coefficient (r) for validity testing. RESULTS: Intertester reliability for the BOT response speed subtest using either mean or median scores for 7 test trials for each subject was ICC[2,1] = 0.99. Test-retest reliability for the BOT was ICC [2,1] = 0.53 using mean scores and ICC[2,1] = 0.65 using median scores. Mean scores from both the first and second administrations of the BOT subtest were correlated with electronic reaction time test scores (r = -0.41 and r = -0.45, respectively; P < .05). Scores improved significantly from the first to the second test administration. CONCLUSIONS: Although intertester reliability was excellent, test-retest reliability for the BOT response speed subtest was not in an acceptable range for this sample of community-dwelling older adults. Further study of optimal methods of administration is needed to develop this measure for use in screening and examination of older adults.

Approximate entropy detects the effect of a secondary cognitive task on postural control in healthy young adults: a methodological report.

BACKGROUND: Biomechanical measures of postural stability, while generally useful in neuroscience and physical rehabilitation research, may be limited in their ability to detect more subtle influences of attention on postural control. Approximate entropy (ApEn), a regularity statistic from nonlinear dynamics, recently has demonstrated relatively good measurement precision and shown promise for detecting subtle change in postural control after cerebral concussion. Our purpose was to further explore the responsiveness of ApEn by using it to evaluate the immediate, short-term effect of secondary cognitive task performance on postural control in healthy, young adults. METHODS: Thirty healthy, young adults performed a modified version of the Sensory Organization Test featuring single (posture only) and dual (posture plus cognitive) task trials. ApEn values, root mean square (RMS) displacement, and equilibrium scores (ES) were calculated from anterior-posterior (AP) and medial-lateral (ML) center of pressure (COP) component time series. For each sensory condition, we compared the ability of the postural control parameters to detect an effect of cognitive task performance. RESULTS: COP AP time series generally became more random (higher ApEn value) during dual task performance, resulting in a main effect of cognitive task (p = 0.004). In contrast, there was no significant effect of cognitive task for ApEn values of COP ML time series, RMS displacement (AP or ML) or ES. CONCLUSION: During dual task performance, ApEn revealed a change in the randomness of COP oscillations that occurred in a variety of sensory conditions, independent of changes in the amplitude of COP oscillations. The finding expands current support for the potential of ApEn to detect subtle changes in postural control. Implications for future studies of attention in neuroscience and physical rehabilitation are discussed.

Gross motor development of children with hurler syndrome after umbilical cord blood transplantation.

BACKGROUND AND PURPOSE: Little is known about the gross motor development of children with Hurler syndrome who have undergone umbilical cord blood transplantation (UCBT). The purpose of this study was to provide a description of gross motor development in children with Hurler syndrome after UCBT. SUBJECTS AND METHOD: Longitudinal changes in gross motor abilities were documented on the gross motor subtests of the Peabody Developmental Motor Scales, second edition (PDMS-2) for 21 children with Hurler syndrome. Each child was assessed between 1 and 6 times after UCBT. The participants had a mean age (+/-SD) of 32.2+/-16.0 months at the time of the first assessment. The mean time (+/-SD) between UCBT and the first assessment was 16.2+/-16.5 months. RESULTS: The participants had marked gross motor delays, with a mean gross motor quotient 2 standard deviations below the mean for children who were developing typically. The rate of development differed between the subtests of the PDMS-2. The participants gained abilities at the slowest rate on the stationary subtest and at the fastest rate on the locomotor subtest. DISCUSSION AND CONCLUSION: The participants had varying degrees of delay in different gross motor domains. While gaining new gross motor abilities over time, these children continued to have delays up to 48 months after UCBT. Physical therapists treating children with Hurler syndrome after UCBT should use assessment tools that will capture these differences and should individualize treatment plans accordingly. Additional research is needed to document the efficacy of physical therapy intervention with this population.