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What is crossing midline and why does it matter?

By Noémie von Kaenel, OTS and Bearfoot OT

Does your child...

  • Use either hand for tasks or switch hands when holding/playing with objects?

  • Have difficulty following items in their visual field (i.e. reading across the page)?

  • Shift their whole body to the side instead of reaching across their body for an object?

  • Rotate the paper 180 degrees to write?

  • Have difficulty drawing shapes without lifting their writing utensil (i.e. not bit by bit)?

These are signs that your kid might have difficulty crossing midline.

Want to know what it is, why it's important, and how you can help your kid improve this skill at home?

Keep reading!

What is crossing midline?

Imagine drawing an imaginary line from the top of your head down the middle of your body, separating your body into right and left sides.

That’s your midline!

Crossing midline means moving any part of your body (hand, arm, foot, leg) past that imaginary line to the other side of your body. This skill first starts to develop in your kid's first year as they learn to reach for a toy, grasp it, bring it to their chest and then play with it with two hands.

Crossing midline takes time to develop because when you do, both sides of your brain communicate with each other through the corpus callosum.

That’s the part of your brain that acts like a bridge of communication between the two hemispheres of the brain. This is necessary for crossing midline because the right side of the brain controls and moves the left side of your body, and the left side of your body controls and moves your right side⁵.

By using both brain hemispheres, more neurons in the brain fire, making more connections!

Crossing midline is important for many reasons, and one is to establish a dominant hand for writing.

Think about how you write (if you are writing English) - you start at the top left corner and write across the page from left to right. If you are right handed, it means you cross midline to start writing because you have to cross your body with your right hand to get to the left side of the page! If you are left handed, you start on your left side, but cross midline halfway through the page if you are writing all the way across.

If your child has difficulty with crossing midline, your child might switch hands when they get to the middle, turn their paper to avoid crossing midline, or shift their whole body to make it easier to write across a whole line with their preferred hand.

How does crossing midline develop?

Feel free to nerd out EVEN MORE about the development of crossing midline here and here.

Why is crossing midline important?

  • Prepares visual tracking across the visual field (tracking something across what you see) for reading⁵ ¹¹

  • Develops hand dominance for handwriting and cutting³ ⁵ ¹¹

  • It’s an important developmental step towards bilateral coordination, used functionally in play and ball skills for sports ³ ⁵ ¹¹ ¹³

  • You use this skill when getting dressed (putting a sock on your right foot with your left hand) or feeding yourself (reaching for food on the other side of your plate)⁷

What to look for...

Some children who have a hard time crossing midline may avoid it completely by turning their body or the materials they’re using. One goal is to support your kid’s core and hip position so they can be stable and reach to both sides of their body.

For example, in this first picture, the body is turning from the hips and core to avoid having to cross the midline.

In the second picture, the core and hips are stable so the body is squared to the table, which means if they were going to reach for the scissors with their right hand, they would cross midline to get there!

You can reinforce crossing midline throughout your kid’s day woven into activities you already do.

For example:

  • Encourage your kid to reach across their body for a glass of water.

  • During handwriting practice, place materials on the opposite side of their dominant hand, so they can reach over and grab what they need.

  • During clean up, place the box or trash can on the non-dominant side so that every time they put a block away, they are crossing midline to do it!

Here are some tips and activities to work on crossing midline

Name the dominant hand the “worker” hand and the non dominant hand the “helper hand.” This can help with kids that are confused about their rights and lefts!

If you are trying to have them use their dominant hand to reach across midline, you can have them hold something in their non-dominant hand to encourage their "helper hand" to stay out of the motion.

Incorporate crossing midline into everyday activities