Babies with typical development show asymmetrical behavior in their lower limb activity during the pulling-to-stand (PTS) stage. This finding emerges from a new study undertaken at the University of Haifa. “From a developmental perspective it is very important to examine and understand the typical normative range of motor development in order to identify individual differences or atypical behavior", notes Dr. Osnat Atun-Einy of the Department of Physical Therapy. Dr. Atun-Einy undertook the study under the supervision of Prof. Anat Scher of the Department of Education and Human Development.
The phenomenon of side preference has fascinated many researchers from different fields as one of the prominent manifestations of brain side dominance. In the past, it was assumed that babies’ brains are symmetrical in structure and function until the age of two years, while functional asymmetries develop at a later stage. Accordingly, leg preference was only studied from three years and above. In the present study, the researchers have for the first time documented evidence of the early development of leg preference in babies during the crawling and PTS stage as part of the normal developmental process.
In their study, the researchers focused on the stage when babies begin to stand up, with support, from a half-kneeling or asymmetric four-point kneeling. The study included 27 healthy babies with normal development aged from seven to 12 months.
The study findings show that 78 percent of the babies showed a clear leg preference when standing from a half-crawl position or from asymmetric four-point kneeling. Moreover, a group of babies was identified that preferred to use the same lead leg in all PTS movements within a few months of acquiring PTS capabilities. The researcher noted that the preferred leg at this stage may not necessarily be the dominant leg at a later stage.
Dr. Atun-Einy explains that the main significance of these findings is that functional asymmetry, with a division of functions between a stabilizing side and a leading side in lower limb functions, is a reflection of anatomical and brain asymmetry. Accordingly, no effort should be made to influence or intervene in this preference. “Clinicians who are unaware of the existence of this phenomenon among the population with typical development may direct their interventions to increase symmetry
in leg function. A better understanding of this process in the normal population will enable us to develop clinical applications for populations with atypical development, and to distinguish between leg preference and abnormal asymmetry,” Dr. Atun-Einy concludes.