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Published on: June 1, 2015
Early changes in muscle activation patterns of toddlers during walking
Chia-Lin Chang1, Masayoshi Kubo, Ugo Buzzi
1Motor Development Laboratory, Division of Kinesiology, The University of Michigan, 401 Washtenaw Avenue, Ann Arbor, MI 48109-2214, USA. changcl@umich.edu
Insights
Toddlers' early walking shows inconsistent muscle activity, with few repeating patterns. With experience, muscle variability decreases, but remains less stable than joint coordination, suggesting a learning process.
Area of Science:
- Developmental motor control
- Biomechanics
- Pediatric kinesiology
Background:
- Early locomotor behavior, specifically infant walking, is a key developmental milestone.
- Limited research exists on the underlying muscle activation patterns during this phase.
- Understanding muscle coordination is crucial for grasping motor development principles.
Purpose of the Study:
- To present an objective method for identifying muscle onset and offset during early walking.
- To investigate the developmental changes in activation patterns of core leg muscles.
- To analyze muscle variability and co-contraction in relation to walking experience.
Main Methods:
- Surface electromyography (EMG) recorded activity from gastrocnemius, tibialis anterior, quadriceps, and hamstrings in eight toddlers.
- Participants were tested at walking onset (3-6 independent steps) and after three months of practice.
- EMG data were analyzed for muscle on-off states, co-contraction, and probability distributions across gait cycles.
Main Results:
- At walking onset, muscle activity was highly variable with minimal recurring patterns within or between toddlers.
- With increased walking experience, muscle activity variability and co-contraction decreased but remained inconsistent.
- This muscle pattern inconsistency contrasted with improved stability in joint coordination and foot placement.
Conclusions:
- Toddlers initially focus on generating sufficient force for balance and progression, exploring numerous muscle activation combinations.
- Optimizing muscle recruitment for efficient locomotion is a gradual learning process.
- The findings highlight a developmental trajectory where motor control refines through experience, prioritizing stability in specific parameters over others.
Abstract:
Early locomotor behavior has been the focus of considerable attention by developmentalists over several decades. Few studies have addressed explicitly patterns of muscle activity that underlie this coordination pattern. Our purposes were to illustrate a method to determine objectively the onset and offset of muscle firings during early walking and to investigate the emergence of patterns of activation of the core locomotor muscles. We tested eight toddlers as they walked overground at walking onset (max. of 3-6 independent steps) and after three months of walking experience. Surface electrodes monitored activity of the gastrocnemius, tibialis anterior, quadriceps, and hamstrings. We reduced EMG signals to a frame-by-frame designation of "on-off," followed by muscle state and co-contraction analyses, and probability distributions for each muscle's activity across multiple cycles. Our results clearly show that at walking onset muscle activity was highly variable with few, if any, muscles showing recurring patterns of behavior, within or among toddlers. Variability and co-activation decreased with walking experience but remained inconsistent, in contrast to the significant increase in stability shown for joint coordination and endpoint (foot placement) parameters. We propose this trend emerges because of the high number of options (muscle combinations) available. Toddlers learn first to marshal sufficient force to balance and make forward progress but slowly discover how to optimize these resources.
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