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Published on: August 30, 2016
Emergence of neuromuscular patterns during walking in toddlers with typical development and with Down syndrome
Chia-Lin Chang1, Masayoshi Kubo, Beverly D Ulrich
1Department of Physical Medicine and Rehabilitation, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA. chc111@pitt.edu
Insights
Toddlers with Down syndrome (DS) and typical development (TD) develop walking by adjusting muscle activity. While both groups improve efficiency, DS toddlers use longer muscle bursts to stabilize joints, reflecting unique neurophysiological constraints.
Area of Science:
- Neuroscience
- Developmental Biology
- Biomechanics
Background:
- Toddlers with Down syndrome (DS) exhibit delayed walking onset, increased joint laxity, and decreased muscle tone compared to typically developing (TD) toddlers.
- The neuromotor system's adaptation during early walking in DS is not well understood.
- Understanding muscle activity emergence is crucial for addressing motor challenges in DS.
Purpose of the Study:
- To investigate the emergence and adaptation of muscle activity patterns during walking in toddlers with DS and TD.
- To compare the neuromotor strategies employed by DS and TD toddlers from walking onset through six months of practice.
- To explore how biomechanical and neurophysiological constraints influence motor control strategies in DS.
Main Methods:
- Monitored core gait muscle activity and leg segment motion in eight toddlers with DS and eight with TD.
- Recorded data during self-selected walking speeds at walking onset and after six months of practice.
- Analyzed muscle burst frequency, duration, and inter-burst intervals to assess neuromotor control strategies.
Main Results:
- Both DS and TD toddlers adopted energy-efficient strategies, decreasing muscle burst frequency and increasing burst duration over time.
- TD toddlers increased inter-burst intervals, indicating improved muscle synergy and relaxation.
- DS toddlers decreased inter-burst intervals but sustained longer muscle bursts, suggesting a strategy for joint stabilization.
Conclusions:
- Toddlers with DS develop unique, yet efficient, neuromotor strategies for walking, characterized by sustained muscle bursts to compensate for joint laxity.
- The findings highlight the interplay of biomechanical and neurophysiological factors in shaping motor development in DS.
- This study provides insights into adaptive motor control mechanisms in toddlers with developmental differences.
Abstract:
During the development of walking, toddlers with Down syndrome (DS) and typical development (TD) face challenges controlling muscles, joints, and body segments. Toddlers with DS have additional challenges including increased joint laxity and decreased muscle tone and show delayed walking onset; the underlying activity of the neuromotor system remains unclear. Here we investigated the emergence of muscle activity from walking onset through 6 months of practice in eight toddlers with DS and eight with TD. We monitored the activity of core gait muscles and motion of leg segments as toddlers walked at their self-selected speeds. At walking onset muscle bursts were frequent with inconsistent burst durations. Over time, both groups of toddlers began to activate their leg muscles by using energy-efficient strategies: decreased muscle burst frequency (Wilks' Lambda=0.364, F(12, 103.476)=4.009, p< .001) and increased muscle burst duration (Wilks' Lambda=0.346, F(12, 71.727)=2.946, p= .002). Toddlers with TD increased normalized inter-burst intervals over time but toddlers with DS decreased these interval durations. By 6 months of experience toddlers with TD showed an efficient synergy among muscles, allowing increased relaxation time between bursts. Toddlers with DS improved the rhythmicity of their muscle burst, sustaining longer bursts but timing remained inconsistent. We propose increased muscle burst duration in toddlers with DS may add control by stabilizing their lax joints. Thus, their similar yet different emergent strategy may reflect their unique biomechanical and neurophysiological constraints and represent an efficient control strategy.
