Suh-Fang Jeng

Energetic Cost and Stability during Human Walking at the Preferred Stride Frequency

Abstract The possibility that preferred modes of locomotion emerge from dynamical and optimality constraints and the energetic and dynamical constraints on preferred and predicted walking frequency are explored in this article. Participants were required to walk on a treadmill at their preferred frequency, at a frequency predicted as the resonance of a hybrid pendulum-spring model of the legs, and at frequencies ±15%, ±25%, ±35% of the predicted frequency. Walking at the preferred and predicted frequencies resulted in minimal metabolic costs and maximal stability of the head and joint actions. Mechanical energy conservation was constant across conditions. The head was more stable than the joints. The joints appeared to be in service of the head in maintaining a stable trajectory. The major findings of this study suggest a complementary relationship between energetic (physiological) and stability constraints in the adoption of a preferred frequency of walking. Multiple subsystems may be involved in constra...

Use of Virtual Reality to Improve Upper-Extremity Control in Children With Cerebral Palsy: A Single-Subject Design

Background and Purpose: Virtual reality (VR) creates an exercise environment in which the intensity of practice and positive feedback can be systematically manipulated in various contexts. The purpose of this study was to investigate the training effects of a VR intervention on reaching behaviors in children with cerebral palsy (CP). Participants: Four children with spastic CP were recruited. Method: A single-subject design (A-B with follow-up) was used. All children were evaluated with 3 baseline, 4 intervention, and 2 follow-up measures. A 4-week individualized VR training program (2 hours per week) with 2 VR systems was applied to all children. The outcome measures included 4 kinematic parameters (movement time, path length, peak velocity, and number of movement units) for mail-delivery activities in 3 directions (neutral, outward, and inward) and the Fine Motor Domain of the Peabody Developmental Motor Scales–Second Edition (PDMS-2). Visual inspection and the 2-standard-deviation–band method were used to compare the outcome measures. Results: Three children who had normal cognition showed improvements in some aspects of reaching kinematics, and 2 children’s change scores on the PDMS-2 reached the minimal detectable change during the intervention. The improvements in kinematics were partially maintained during follow-up. Discussion and Conclusion: A 4-week individualized VR training program appeared to improve the quality of reaching in children with CP, especially in children with normal cognition and good cooperation. The training effects were retained in some children after the intervention.

International comparisons of behavioral and emotional problems in preschool children: Parents' reports from 24 societies

International comparisons were conducted of preschool childrens behavioral and emotional problems as reported on the Child Behavior Checklist for Ages 1½–5 by parents in 24 societies (N = 19,850). Item ratings were aggregated into scores on syndromes; Diagnostic and Statistical Manual of Mental Disorders–oriented scales; a Stress Problems scale; and Internalizing, Externalizing, and Total Problems scales. Effect sizes for scale score differences among the 24 societies ranged from small to medium (3–12%). Although societies differed greatly in language, culture, and other characteristics, Total Problems scores for 18 of the 24 societies were within 7.1 points of the omnicultural mean of 33.3 (on a scale of 0–198). Gender and age differences, as well as gender and age interactions with society, were all very small (effect sizes < 1%). Across all pairs of societies, correlations between mean item ratings averaged .78, and correlations between internal consistency alphas for the scales averaged .92, indicating that the rank orders of mean item ratings and internal consistencies of scales were very similar across diverse societies.

Prognostic factors for walking attainment in very low-birthweight preterm infants

The purpose of this study was to compare the age of walking attainment between very low-birthweight (VLBW) preterm infants and normal term infants, and to determine the variables that affect the walking attainment in VLBW infants. Ninety-six VLBW preterm infants and 82 normal term infants were prospectively followed to determine their age of walking attainment and to monitor gross motor development with sequential clinic visits at 6, 9, 12 and 18 months corrected age. Perinatal and sociodemographic data were collected through review of medical records. The VLBW infants were significantly older at attainment of walking (median 14 months) than the term infants (median 12 months) after correction for prematurity. By the age of 18 months, all term infants had attained walking ability; while 11% of VLBW infants were still unable to walk. Multivariate proportional hazards regression analysis revealed that low gestational age was significantly associated with late attainment of walking in VLBW infants. With the adjustment for gestational age, prolonged ventilation (or oxygen therapy) and severe retinopathy of prematurity were significant predictors of late walking attainment. Our findings indicate that VLBW preterm infants have an increased risk of delayed attainment of walking. Furthermore, the contribution of low gestational age to the delayed walking attainment in VLBW infants may occur via the plausible pathways of neonatal respiratory distress and severe retinopathy of prematurity.

In utero exposure to environmental lead and manganese and neurodevelopment at 2 years of age.

BACKGROUND AND OBJECTIVE Manganese, lead, arsenic and mercury are common neurotoxic metals in the environment. Nonetheless, the relationship between prenatal exposure to low doses of neurotoxic metals and neurodevelopment in children is not clear. The objective of this study was to explore the relationship between in utero exposure to environmental neurotoxic metals and neurodevelopment at 2 years of age. METHODS The population of this study came from the Taiwan Birth Panel Study. We included 230 pairs of non-smoking mothers without any occupational exposure and their singleton full-term children. The information about exposure during pregnancy was obtained using a structured questionnaire, and the manganese, lead, arsenic and mercury levels in umbilical cord blood samples were analyzed using inductively coupled plasma mass spectrometry. We used the Comprehensive Developmental Inventory for Infants and Toddlers (CDIIT) to evaluate the developmental status of each child at 2 years of age, and we examined the association of in utero exposure to environmental metals and neurodevelopment using linear regression models. RESULTS The median concentrations of manganese, lead, arsenic and mercury in the cord blood samples in this study were 47.90 µg/L (range, 17.88-106.85 µg/L), 11.41 µg/L (range 0.16-43.22 µg/L), 4.05 µg/L (range, 1.50-12.88 µg/L) and 12.17 µg/L (range, 1.53-64.87 µg/L), respectively. After adjusting for maternal age, infant gender, environmental tobacco smoke during pregnancy and after delivery, Home Observation for Measurement of the Environment Inventory results, and arsenic and mercury levels in cord blood, we found that manganese and lead levels above the 75th percentile had a significant adverse association with the overall (β=-7.03, SE=2.65, P=0.0085), cognitive (β=-8.19, SE=3.17, P=0.0105), and language quotients (β=-6.81, SE=2.73, P=0.0133) of the CDIIT. CONCLUSIONS In utero exposure to environmental manganese and lead may have an adverse association with neurodevelopment at 2 years of age, and there is an interaction effect between the manganese and lead levels in the cord blood that could aggravate the effect.

Nationwide singleton birth weight percentiles by gestational age in Taiwan, 1998-2002.

There are limited nationwide population-based data about birth weight percentiles by gestational age in Taiwan. The purpose of this study was to develop updated intrauterine growth charts that are population based and contain the information of birth weight percentiles by gestational age for singleton newborns in Taiwan. We abstracted and analyzed the birth registration database from the Ministry of the Interior in Taiwan during the period of 1998-2002 that consisted of over one million singleton births. Percentiles of birth weight for each increment of gestational week from 21 to 44 weeks were estimated using smoothed means and standard deviations. The analyses revealed that birth weight rose with advancing gestational age, with greater slopes during the third trimester and then leveled off beyond 40 weeks of gestational age. The male to female ratio ranged from 1.088 to 1.096. The mean birth weights during the period of 1998-2002 were higher than those previously reported for the period of 1945-1967; while the birth weight distribution and percentile during the period of 1998-2002 were similar to those reported for the period of 1979-1989. The 10th, 50th, and 90th percentiles of birth weigh at 40th gestational age among the male newborns were 2914, 3374, and 3890 g respectively; and for the female newborns 2816, 3250, and 3747 g. At the gestational age of 37 weeks, the 10th, 50th, and 90th percentiles of birth weigh among the male newborns were 2499, 2941, and 3433 g respectively; and for the female newborns 2391, 2832, and 3334 g. From 1998 to 2002, there was a gradual increase in the prevalence of low birth weight and preterm birth together with the percentage of infants born to foreign-born mothers. This study provides the first nationwide singleton intrauterine growth charts in Taiwan that are population-based and gender-specific. The normative data are particularly useful for the investigation of predictors and outcomes of altered fetal growth.

Kinematic Analysis of Kicking Movements in Preterm Infants With Very Low Birth Weight and Full-Term Infants

Background and Purpose. Study of kicking development provides important information to understand how early spontaneous movements change in infants as they acquire voluntary control. Researchers have investigated the kicking movements of preterm infants; however, the movement patterns that they have described were inconsistent. The purpose of this study, therefore, was to examine the development of kicking movements with kinematic analysis in preterm infants with very low birth weight (VLBW) and full-term infants. Subjects and Methods. Twenty-two infants with VLBW who were divided into low gestational age (gestational age of <30 weeks, n=9) and high gestational age (gestational age of ≥30 weeks, n=13) classes and 22 full-term infants were evaluated during kicking movements using 4 synchronized cameras and 3-dimensional kinematic analysis when the infants were 2 and 4 months of corrected age. Results. The infants with VLBW and a high gestational age showed similar kicking movements compared with the full-term infants. In contrast, the infants with VLBW and a low gestational age exhibited a higher kick frequency and a shorter flexion phase at 4 months of corrected age. They also exhibited a higher hip-knee correlation and lower variability in the interlimb coordination pattern at 2 and 4 months of corrected age. Discussion and Conclusion. The findings indicate that infants with VLBW, particularly those with a low gestational age, have age-related differences in movement organization and coordination of kicking compared with full-term infants.

Optimization of walking in children

Previous work demonstrated that adults naturally adopt a walking frequency to optimize physiological cost, symmetry, and stability. Furthermore, the optimal frequency is predictable using the force-driven harmonic oscillator (FDHO) model. However, no studies have established the developmental processes of optimization in children. Thus, the purposes of this study were to examine the predictability of the preferred stride frequency (PSF) and optimization features of 3- to 12-yr-old children using the FDHO model. Forty-five children and nine adults were measured for anthropometric data to calculate the predicted frequency. They later walked at three frequencies (PSF, PSF +25%, and PSF -25%) at a constant speed on a treadmill. The results indicated that the FDHO model was accurate in predicting the preferred frequency of children (prediction error < 0.07 s). We identified three stages of learning in the development of optimization: an early manifestation of sensitivity to resonant frequency, the subsequent development of ability to modulate walking frequency, and the final establishment of an adult optimization form at age seven. Our findings suggest that walking development may be determined by the dynamic cooperation of physiological, neural, and musculoskeletal systems with respect to the environmental context.

Perfluorinated compound levels in cord blood and neurodevelopment at 2 years of age.

Background: Epidemiologic data regarding the potential neurotoxicity of perfluorinated compounds (PFCs) are inconclusive. We investigated the associations between in utero exposure to perfluorooctanoic acid (PFOA) and perfluorooctyl sulfonate (PFOS) and early childhood neurodevelopment. Methods: We recruited 239 mother–infant pairs in northern Taiwan from the Taiwan Birth Panel Study, which was established in 2004. We examined the association between PFCs in cord blood and children’s neurodevelopment at 2 years of age, using the Comprehensive Developmental Inventory for Infants and Toddlers. This tool contains cognitive, language, motor, social, and self-help domains; test scores were further transformed into developmental quotients according to standardized norms. All multivariate regression models were adjusted for infant sex and gestational age, maternal education, family income, cord blood cotinine levels, postnatal environmental tobacco smoke exposure, and breastfeeding. Results: Prenatal PFOS concentrations in both untransformed and natural log (Ln)-transformed values were associated with adverse performance on the whole test and the domains related to development. A dose–response relationship was observed when PFOS levels were categorized into four groups. This association was most obvious in relation to the gross-motor subdomain. Across the PFOS interquartile range, the quotients of the gross-motor subdomain decreased by 3.7 points (95% confidence interval [CI] = −6.0 to −1.5), with an increasing odds ratio of poor performance (2.4; 95% CI = 1.3 to 4.2). In contrast, measures of association between PFOA concentrations and test scores were close to null. Conclusions: Prenatal exposure to PFOS, but not PFOA, may affect children’s development, especially gross-motor development at 2 years of age.

DEVELOPMENTAL FUNCTION OF VERY-LOW-BIRTH-WEIGHT INFANTS AND FULL-TERM INFANTS IN EARLY CHILDHOOD

BACKGROUND AND PURPOSE Despite general recognition that surviving very-low-birth-weight (VLBW) infants are at risk for neurodevelopmental impairments and educational achievement difficulties, there has been relatively little study on their functional status in areas such as locomotion, communication, cognition, self-care, and interpersonal relationships. This study assessed the functional status of VLBW infants and full-term infants in early childhood, and sought to identify risk factors for functional morbidity. METHODS A total of 238 VLBW infants and 91 full-term infants were included in this prospective follow-up study. The functional status of the infants was assessed using the Chinese Child Development Inventory (CCDI) and neurodevelopment was evaluated using the Bayley Scales of Infant Development, second version (BSID-II) at 3 years of corrected age. Perinatal and sociodemographic data were collected through review of medical records. RESULTS The VLBW infants had lower scores on all the CCDI measures compared with the full-term infants. Functional limitation (defined as more than 2 standard deviations below the means of the full-term infants) occurred more frequently in the VLBW infants than in the full-term infants: gross motor, 23% vs 3%; fine motor, 12% vs 1%; expressive language, 21% vs 2%; comprehension-conceptual, 23% vs 4%; situation comprehension, 17% vs 4%; self-help, 17% vs 1%; and personal-social, 19% vs 3% (all p < 0.01). Significant risk factors associated with functional morbidity included gestational age < 30 weeks, grade III-IV intraventricular hemorrhage, chronic lung disease, stage III-IV retinopathy of prematurity, male gender, and maternal education below high school. CONCLUSION VLBW infants have a higher risk of functional morbidity than their full-term counterparts in early childhood. Infants with functional limitations on CCDI screening might require comprehensive developmental assessment and continued follow-up.