Learning to Roll
Authors: Siegel Danielle N. 
Published: January 2025

Motor skills, like rolling, are an important part of an infant’s cognitive and
motor development by facilitating interactions with others and their surrounding
environment. Additionally, an infant’s musculoskeletal and motor development is
largely affected by their environment and in the U.S., infants spend a majority
of their time in commercial infant products, including those at an incline. The
biomechanical impacts of infants spending time at an incline is an understudied
area, and almost 12,000 emergency room visits occur each year due to injuries
involving commercial infant products. Therefore, the overall objective of this
study was to understand how an infant’s muscle utilization and coordinated
movements are affected by varying mechanical environments.

We first created methodology that allowed for the accurate identification of
infant rolling coordinated movements through video alone. This validated
video-based methodology allows both researchers and clinicians to identify
infant rolling movements quickly and effectively without the use of motion
capture technology. Second, the muscle utilization of the different coordinated
movements was quantified on a firm flat surface, providing a baseline for
comparison when looking at rolling in different mechanical environments.
Finally, how rolling is affected by different mechanical environments,
specifically seatback incline, was determined. We identified how rolling
techniques and muscle utilization change at varying seatback inclines and for
the various coordinated movements of rolling.

Our results indicate that each coordinated movement of rolling can be identified
between different reviewers with substantial agreement, expanding the
accessibility of infant rolling identification for research and clinical
diagnoses. We also determined that each coordinated movement has a unique muscle
utilization pattern, and these muscle utilization patterns can change based on
the mechanical environment in which an infant is placed. In the mechanical
environments we tested, we also discovered a new coordinated movement that was
not exhibited on the flat surface alone. Furthermore, we found that at inclines
of just 10° infants exhibited significantly higher erector spinae muscle
activation and significantly lower abdominal muscle activation when compared to
the flat surface. With these increasing inclines, an infant’s choice in rolling
maneuver also significantly changed. When testing with a seatback angle of 0°,
comparable to the flat surface, an infant’s hamstring and quadricep muscle
activation was significantly higher than that of the flat surface, indicating
that infants are interacting with products independent of the incline.

This body of work is the first that we know of that (1) identifies the
coordinated movements of rolling with video-based methodology, (2) defines the
muscle utilization patterns of infant rolling on a flat surface, and (3)
determines how rolling is affected by different mechanical environments. Results
from this study can provide more insight into motor development and may inform
the juvenile products industry to mitigate unexpected rolling and potential
injuries within commercial infant products.