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Updated: May 23, 2026
Quantifying Learning in Young Infants: Tracking Leg Actions During a Discovery-learning Task
Published on: June 1, 2015
Longitudinal changes in muscle activity during infants' treadmill stepping
Caroline Teulier1, Jennifer K Sansom, Karin Muraszko
1Laboratoire Psychologie de la Perception, Centre National de la Recherche Scientifique, Université Paris Descartes, Paris, France.
Insights
Infant treadmill stepping shows improved movement control with age, but muscle activation patterns remain highly variable. Stable neural control for this novel task develops with functional practice, not just innate maturation.
Area of Science:
- Developmental motor control
- Infant biomechanics
- Neuromuscular development
Background:
- Previous studies on treadmill stepping kinetics used cross-sectional designs.
- Infant motor development involves refining kinematic and kinetic strategies.
- Understanding muscle activation patterns is key to infant motor learning.
Purpose of the Study:
- To longitudinally examine muscle activation patterns during unpracticed treadmill stepping in healthy infants.
- To correlate kinematic changes with underlying muscle activity over the first year of life.
- To investigate the development of neural control strategies for infant stepping.
Main Methods:
- Longitudinal study of 12 healthy infants at 1, 6, and 12 months of age.
- Assessment of muscle activation (electromyography) of lateral gastrocnemius, tibialis anterior, rectus femoris, and biceps femoris during treadmill stepping.
- Analysis of kinematic variables including step frequency and foot contact patterns.
Main Results:
- Infants demonstrated improved kinematics, including increased step frequency and altered foot contact.
- High variability in muscle activation patterns was observed, decreasing with age.
- Agonist-antagonist muscle coactivation reduced with age, while lateral gastrocnemius showed adult-like probability patterns.
Conclusions:
- Infant kinematic stability during treadmill stepping improves more than underlying kinetic strategies.
- While innate motor control improves, stable neural activation for novel tasks like treadmill stepping requires functional practice.
- Motor learning and practice are crucial for developing robust neuromuscular control in infancy.
Abstract:
Previous research has described kinetic characteristics of treadmill steps in very stable steppers, in cross-sectional designs. In this study we examined, longitudinally, muscle activation patterns during treadmill stepping, without practice, in 12 healthy infants at 1, 6, and 12 mo of age. We assessed lateral gastrocnemius, tibialis anterior, rectus femoris, and biceps femoris as infants stepped on a treadmill during twelve 20-s trials. Infants showed clear changes in kinematics, such as increased step frequency, increased heel contact at touch down, and more flat-footed contact at midstance. Electromyographic data showed high variability in muscle states (combinations), with high prevalence of all muscles active initially, reducing with age. Agonist-antagonist muscle coactivation also decreased as age increased. Probability analyses showed that across step cycles, the likelihood a muscle was on at any point tended to be <50%; lateral gastrocnemius was the exception, showing an adultlike pattern of probability across ages. In summary, over time, healthy infants produce a wide variety of muscle activation combinations and timings when generating stepping patterns on a treadmill, even if some levels of muscle control arose with time. However, the kinematic stability improved much more clearly than the underlying kinetic strategies. We conclude that although innate control of limb movement improves as infants grow, explore, and acquire functional movement, stepping on a treadmill is a novel and unpracticed one. Hence, developing stable underlying neural activations will only arise as functional practice ensues, similarly to that observed for other functional movements in infancy.
