Just Add Weight: The Relation between Upper-Extremity Weight-Bearing and the Development of Thumb Opposition in Infants

Overview

Objectives/Goals Human infants are not born with the ability to move their fingers independently or rotate the thumb so that the pad of the thumb is opposed to the pad of the index finger. From 6-12 months of age, infants' grasping patterns improve rapidly and become increasingly precise, primarily due to increased involvement of the thumb. This study investigated whether the specific experience of repeatedly weighting the hands when crawling on hands-and-knees facilitates the development of thumb opposition in infants 9.5 and 10.5 months of age. Methods/Materials The sample included 42 infants who had been crawling for different lengths of time. To determine the area of weight-bearing (pressure) on the hands, the undersides of infants# hands were videotaped as they crawled across an elevated Plexiglas surface. Weight-bearing was defined as the total area of pressure in mm^2 on the right and left hand/total area of the two hands during maximum weight-bearing. Thumb opposition was assessed individually for each hand by examining thumb involvement as the infants grasped and lifted an alphabet cube. Results As predicted, a one-way ANOVA revealed a significant positive association between total area of weight-bearing on the hands and finger/thumb opposition score. Further work is needed to determine if the link between weight-bearing and thumb opposition is causal. A Chi-square analysis revealed significant positive association between weeks crawling and finger/thumb opposition score. In contrast, an analysis of the relation between age and finger/thumb opposition score did not reach significance. Although it is possible that brain maturation could account for both crawling and thumb opposition in this sample, similar scores between 9.5- and 10.5-month-old infants suggest that this explanation is unlikely. Taken together, these findings suggest that the experience of weighting the hands repeatedly over many weeks may facilitate the development of finger/thumb opposition and infant hand development Conclusions/Discussion Finger/thumb opposition is essential to the precision with which we grasp. Although weight-bearing is currently used as a treatment technique by pediatric physical and occupational therapists to improve hand function in children, this study is one of the first to provide evidence that the technique may have value.

Awards (1)

• First Place

Competition history

• CSEF 2007 Mammalian Biology · Entry S1110

Resources

• CSEF project summary ↗

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