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Updated: Sep 22, 2025
Quantified Assessment of Infant's Gross Motor Abilities Using a Multisensor Wearable
Published on: May 17, 2024
Unweighting infants reveals hidden motor skills
Tracy Kornafel1, Athylia C Paremski2, Laura A Prosser2,3
1Department of Physical Therapy, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA.
Insights
Infants can stand and walk earlier than expected when their body weight is reduced. This suggests that motor control develops before muscles and balance are ready for walking.
Area of Science:
- Developmental science
- Motor development
- Infant locomotion
Background:
- Bipedal posture and locomotion are key infant developmental milestones.
- Poor balance and weak muscles are traditionally considered rate-limiting factors for walking.
- Investigating these factors can reveal underlying motor skills.
Purpose of the Study:
- To investigate the role of rate-limiting factors in infant development using walking as a model.
- To determine if reducing body weight (unweighting) reveals emergent upright motor skills.
- To assess the relationship between unweighting effects and infants' prior locomotor experience.
Main Methods:
- Unweighted prewalking infants using a specialized system.
- Measured standing and walking behaviors under different unweighting conditions (20% and 40%).
- Compared performance to baseline and analyzed the influence of locomotor experience.
Main Results:
- Infants stood unsupported for longer durations with 20% or 40% unweighting.
- 40% unweighting increased independent steps and steps with one hand held.
- No significant differences were observed in transitions to/from standing.
- Locomotor experience influenced unweighting effects during cruising and push-toy walking.
Conclusions:
- Unweighting revealed more advanced motor skills, including longer unsupported standing and independent walking.
- Motor control refinement for bipedalism appears to precede functional emergence of these skills.
- Musculoskeletal development may be a rate-limiter compared to neurological factors.
- Unweighting interventions could be beneficial for infants with motor delays.
Abstract:
We investigated the role of rate limiting factors in development using walking as a model system. The achievement of bipedal posture and locomotion are among the most significant achievements in an infant's first year, with poor balance and weak muscles long proposed as the rate limiting factors. Compensating for either may reveal upright motor skill that has not yet emerged in the infant's natural repertoire. To probe this question, we unweighted prewalking infants and measured their performance in various standing and walking behaviors while unweighted compared to baseline. Our secondary objective was to determine if the influence of unweighting was related to infants' locomotor experience. Infants stood unsupported for longer durations with 20% or 40% unweighting. Infants took more independent steps and more steps with one hand held with 40% unweighting. No differences in transition to/from standing were observed. Locomotor experience was related to the influence of unweighting during cruising and walking with a push toy. This is the first report of more advanced motor skills-longer periods of unsupported standing and the emergence of independent walking-revealed by unweighting infants. We interpret our observations to suggest that the refinement of motor control needed to support bipedal posture and locomotion precedes the functional emergence of these skills in infants. In other words, the musculoskeletal components required for walking are slower to develop than the neurological factors - and consequently may be the rate limiters. We further suggest that training regimens including unweighting should be explored in infants with motor delays.
