ABSTRACT
OBJECTIVES: This study investigated differences in reactive balance abilities of typically developing children and those with spastic diplegia. Recovery from balance threats was compared by: (i) Platform velocity and amplitude thresholds: Speed and size of platform movement at which children required assistance to remain upright, (ii) percentage of trials with feet-in-place vs. loss of balance, and (iii) center of pressure measures. Participants included 8 children with spastic diplegic cerebral palsy, 15 developmentally matched children (similar walking stages) and 21 age-matched control children. METHODS: Backward platform movements graded as easy, moderate and difficult were unexpectedly imposed on children standing on a moveable platform. RESULTS: Children with cerebral palsy (CP) had lower platform velocity thresholds, greater percentages of loss of balance trials, increased distances and increased frequency of directional changes in center-of-pressure (COP) trajectories than control children. Older children with CP fell more often than those under 5 years. Greatest differences between children with and without CP were found in comparisons based on age rather than developmental levels. CONCLUSIONS: Using balance perturbations that challenged children with CP to the limits of their balance abilities effectively identified age performance differences and differences compared to typically developing children. Implications for rehabilitation programs are presented.
Subject(s)
Adaptation, Physiological/physiology , Cerebral Palsy/physiopathology , Child Development/physiology , Postural Balance/physiology , Age Factors , Case-Control Studies , Child , Child Behavior , Child, Preschool , Female , Humans , Male , Motor Skills/physiology , Movement/physiology , Posture/physiology , Pressure , Walking/physiologyABSTRACT
This study aimed to test mechanisms underlying impairments in balance control in children with cerebral palsy. We hypothesized that balance loss during large/fast perturbations could be due to reduced contraction of agonist muscles, delay in muscle contraction or simultaneous contraction of antagonist muscles, reducing the efficiency of the agonist burst. Electromyograms were recorded as children recovered from balance threats of varying magnitudes/velocities. In typically developing children muscle response magnitudes increased with larger/faster perturbations, while in children with cerebral palsy they did not. There was no difference in muscle onset latency or antagonist co-contraction between groups. Thus the primary constraint on balance recovery in these children is insufficient levels of contraction of agonist postural muscles.
Subject(s)
Adaptation, Physiological/physiology , Cerebral Palsy/physiopathology , Muscle Contraction/physiology , Posture/physiology , Child , Child, Preschool , Electromyography , Humans , Mechanoreceptors/physiology , Muscle Spasticity/physiopathology , Muscle, Skeletal/innervation , Muscle, Skeletal/physiology , Postural Balance/physiologyABSTRACT
Developmental changes in the kinematics and kinetics underlying balance control were studied in 61 children, 9 months to 10 years of age. The children were classified according to developmental milestones as standers; new, intermediate, and advanced walkers; runners-jumpers; hoppers; gallopers; and skippers. The children experienced support-surface translations of varying size and speed. Children with greater locomotor experience withstood larger balance threats without collapsing or stepping. Analyses of scaled trials (perturbations normalized in size to foot length and center of gravity height) revealed that improvement in balance was not related to initial configuration parameters surrounding the task (degree of crouch or lean). Children with advanced locomotor skills had faster recovery times and relatively larger muscle torques than children with less experience. Relative torque-time histories of the more experienced children began to match the adult response to similar perturbations. With increased experience and changing muscle torque regulatory abilities, balance skills became more robust.
Subject(s)
Leg/physiology , Postural Balance , Child , Child Development/physiology , Child, Preschool , Female , Humans , Infant , Kinetics , Male , Motor Skills/physiology , Spatial Behavior/physiology , TorqueABSTRACT
The development of the ability to use the step for balance recovery was studied among twenty-five 9- to 19-month-old children. The children were grouped according to walking experience (4 levels) and exposed to backward support surface translations, 8 cm in amplitude, under 3 velocity conditions: 15, 20, and 25 cm/s. New walkers (up to 2 weeks' walking experience) used the step infrequently and ineffectively in response to threats to balance. Intermediate walkers (1-3 months' walking experience) showed an increasing use of the step and significant improvement in step execution compared with new walkers. Advanced walkers (>3; months' walking experience) experienced no falls throughout the protocol, capturing balance with feet-in-place or step responses under all perturbation conditions. A significant developmental transition in the emergence of the compensatory step occurred between the new walker and the intermediate walker experience levels, that is, within the first 3 months of walking experience. Three to 6 months' experience was required for the development of an effective stepping response. A concomitant change in mediolateral stability paralleled the emergence of compensatory stepping.
