The midline is an imaginary vertical line that moves down the middle of the body from head to toes. Crossing this line is when one reaches their left arm/leg to the right side of the body or the right arm/leg to the left side of the body. It is important that the child avoids rotating their trunk when performing this reach, in order to truly cross the midline.
Infants learn to grasp objects with one or both hands around 3-6 months after birth. Infants learn to reach across the midline to grasp objects at about 5-7 months after birth. This is an important milestone for infants as it expands their environments for tactile exploration and manipulation of objects. Crossing the midline can increase independence in self-care skills. It increases bilateral coordination and fine motor skills; it also improves the communication between the two hemispheres of the brain.
Ways to promote your child’s ability to cross the midline can include a variety of activities:
Clapping hands or touching two objects together at the midline.
Catching, throwing, or kicking a ball.
Asking the child to reach for items on opposite side of the arm they use.
Art activities in which they draw/color on opposite side of paper than the arm they use.
These are just some of the many ways you can get creative and have fun teaching your child how to engage in crossing the midline.
Van Hof, P., Van Der Kamp, J., Savelsbergh, G. J. P., Van Hof, R., & Savelsbergh, G. J. R. (2002). The relation of unimanual and bimanual reaching to cross the midline. Child Development, 73(5), 1353-1362. https://doi.org/10.1111/1467-8624.00476
“What Is Crossing the Midline and Why Is It Important?” Child Development Centre, 24 Jan. 2018, https://www.cdchk.org/parent-tips/what-is-crossing-the-midline/.