Ann F. VanSant

Trunk and Hip Muscle Activation Patterns Are Different During Walking in Young Children With and Without Cerebral Palsy

Background Poor control of postural muscles is a primary impairment in people with cerebral palsy (CP). Objective The purpose of this study was to investigate differences in the timing characteristics of trunk and hip muscle activity during walking in young children with CP compared with children with typical development (TD). Methods Thirty-one children (16 with TD, 15 with CP) with an average of 28.5 months of walking experience participated in this observational study. Electromyographic data were collected from 16 trunk and hip muscles as participants walked at a self-selected pace. A custom-written computer program determined onset and offset of activity. Activation and coactivation data were analyzed for group differences. Results The children with CP had greater total activation and coactivation for all muscles except the external oblique muscle and differences in the timing of activation for all muscles compared with the TD group. The implications of the observed muscle activation patterns are discussed in reference to existing postural control literature. Limitations The potential influence of recording activity from adjacent deep trunk muscles is discussed, as well as the influence of the use of an assistive device by some children with CP. Conclusions Young children with CP demonstrate excessive, nonreciprocal trunk and hip muscle activation during walking compared with children with TD. Future studies should investigate the efficacy of treatments to reduce excessive muscle activity and improve coordination of postural muscles in CP.

Trunk and hip muscle activity in early walkers with and without cerebral palsy--a frequency analysis.

Poor control of postural muscles is a primary impairment in cerebral palsy (CP), yet core trunk and hip muscle activity has not been thoroughly investigated. Frequency analysis of electromyographic (EMG) signals provides insight about the intensity and pattern of muscle activation, correlates with functional measures in CP, and is sensitive to change after intervention. The objective of this study was to investigate differences in trunk and hip muscle activation frequency in children with CP compared to children with similar amounts of walking experience and typical development (TD). EMG data from 31 children (15 with CP, 16 with TD) were recorded from 16 trunk and hip muscles bilaterally. A time-frequency pattern was generated using the continuous wavelet transform and instantaneous mean frequency (IMNF) was calculated at each interval of the gait cycle. Functional principal component analysis (PCA) revealed that IMNF was significantly higher in the CP group throughout the gait cycle for all muscles. Additionally, stride-to-stride variability was higher in the CP group. This evidence demonstrated altered patterns of trunk and hip muscle activation in CP, including increased rates of motor unit firing, increased number of recruited motor units, and/or decreased synchrony of motor units. These altered muscle activation patterns likely contribute to muscle fatigue and decreased biomechanical efficiency in children with CP.

Variability and symmetry of gait in early walkers with and without bilateral cerebral palsy

PURPOSE Investigating gait characteristics during the early stages of walking in CP may contribute to the understanding of the development of impaired gait. The objective of this study was to investigate differences in the variability and symmetry of spatiotemporal gait characteristics during the early years of walking in children with bilateral spastic CP compared to children with similar amounts of walking experience and typical development (TD). METHODS The spatiotemporal gait parameters of 31 children (15 with spastic CP, 16 with TD) who had an average of 28.5 (18.1 SD) months of walking experience were collected using an instrumented walkway. RESULTS All primary spatiotemporal parameters were reduced in the CP group, who also demonstrated greater stride-to-stride variability, compared to the TD group. There were no statistically significant differences in side-to-side symmetry between groups. IMPLICATIONS Clinical trials investigating gait interventions during the early years of walking in children with CP should be conducted to determine if treatment can reduce the functional limitations that are present during the emergence of walking skills. Further investigation should examine variability and symmetry in the kinematics, kinetics, and muscle activity patterns of early walkers with CP, and the effect of treatment on the variability and symmetry of walking characteristics.

Changes in Throwing by Older Adults: A Longitudinal Investigation

This investigation examined change in a motor pattern requiring multisegmented coordination in older adults. The overarm throw was observed longitudinally in 8 elderly individuals over 7 years. Data were evaluated using Robertons (Roberton & Halverson, 1984) movement components. Contrasting the assumed pattern of aging, only small declines in movement form were observed. Individual cases revealed additional, noncategorizable declines within component categories, including slower movement speed and decreased range of motion. Increased trial-to-trial variability also was associated with change. These changes suggested that elderly participants coordinated their movements in a manner similar to younger participants but controlled them differently. The small changes observed in this investigation suggest that performance, at least for some skills, is more stable than traditionally assumed.

THROWING PATTERNS OF OLDER ADULTS: A FOLLOW -UP INVESTIGATION·

Previous investigations of the movement patterns of older adults have focused on functional movements. Performance declines have been reported with increasing age. Many investigations, however, do not require older adults to perform maximal, force producing actions. Smaller declines might be observed if older adults made a maximal effort. This investigation examined changes in a maximal skill—the overarm throw for force. Active, older adults were videotaped as they threw tennis balls. Thirteen people were filmed for two consecutive years. Gender and age differences were examined for movement patterns, ball velocity, and selected kinematic measures. Participants threw using patterns and velocities generally observed in children in middle elementary-school years. This result suggested there was a decline in this force production skill. Some older adults regressed in the movement patterns they used over the two years of testing. Older males threw faster, using more advanced movement patterns than older females.

A Life Span Concept of Motor Development

A concept of life span motor development is presented. Evolution of the authors concept of motor development is traced from its beginnings in classic developmental theory rooted in the biological sciences. Influenced by contemporary motor control theory and the writings of Milani-Comparetti, mechanistic models of nervous system function were abandoned in favor of active organism concepts. Application of classic developmental theory to the practice of physical therapy led to a specific focus on righting behaviors and eventual discovery of the limitation of classical neurodevelopmental theory for the explanation of adult motor behaviors. The authors current research focus is summarized; it was formulated from a perspective of lifelong development and is directed toward describing age related movement patterns in a series of righting tasks.