What is “crossing the midline?”
You might hear your child’s therapist tell you that they worked on crossing their midline during a session, but what does that mean and why is it important? Crossing the midline is the ability to move one body part (ex: hand, foot, eye, or tongue) across the center of the body to the other half of the body. Reaching with your right hand to scratch your left elbow as an example of crossing your midline. This is also the skill used when we read and write from left to right, draw a rainbow from one side of the paper to the other, and reach down to tie our shoes with both hands. The ability to fluidly cross the midline develops between the ages of 3 and 4 years old, as the child experiences and engages in more activities that require coordination of the two sides of the body (bilateral coordination). Movements that cross the midline help to build neural pathways and connections in the brain to support the development of motor and cognitive skills that are foundational to reading, writing, self-care, and play.
Why do some children have difficulty with crossing the midline?
Crossing the midline requires a combination of motor and perceptual skills that may be affected by underlying sensory difficulties. This skill relies on accurate body awareness, or the perceptual ability to understand where the body is in space. Crossing the midline is dependent on receiving adequate vestibular and proprioceptive from our sensory systems to understand where our body parts are in space and in relation to each other. The ability to cross the midline may also be affected by a retained Asymmetrical Tonic Neck Reflex (ATNR). This primitive reflex, also known as the “fencer’s pose,” is seen when a baby’s head is turned to one side. The arm and leg on the side of the body the head is turned toward extend, while the arm and leg on the opposite side of the body flex. This reflex is important for babies to develop muscle tone, visual attention and hand-eye coordination. However, it is expected to be integrated into the nervous system by the time an infant is 5 to 7 months old. A retained ATNR may have several functional implications, including:
- Difficulty with hand-eye coordination
- Difficulty with handwriting
- Difficulty with visual tracking
- Difficulty crossing the midline
- Delayed hand dominance
- Difficulty with balance
What activities can help with crossing the midline?
Activities that support crossing the midline help to create new neural pathways to integrate a retained ATNR, and support skills required for handwriting, visual tracking, and catching and throwing games. Here are a few simple ideas to incorporate practicing crossing the midline into play and everyday activities with your child:
- Set up a favorite puzzle or game with the pieces split into piles on each side of your child as they sit or lay on the floor, or sit on a yoga ball. Encourage them to use their opposite arm to grab the pieces on either side of them (i.e. cue “reach with your right arm” to get the pieces on their left side).
- Blow bubbles and encourage your child to pop them using their fingers. Bubbles promote visual tracking, bilateral coordination and crossing the midline with natural, fluid movements.
- Blow up a balloon and hit it back and forth to play balloon volleyball. For older children, ask them to hit it with the opposing hands to facilitate crossing the midline. If your child doesn’t know the difference between their right and left hands, put stickers on their hands and cue for the different sticker colors.
- Draw rainbows, figure-8s, and infinity signs on paper taped to a wall for a vertical surface. Make the activity even more exciting by drawing these figures extra large with sidewalk chalk outside. You can mix up the sensory feedback by trying this activity with shaving cream, sand, etc.
- Set up a “drum set” made of pots, pans, and other objects around the house. Encourage your child to cross their midline by hitting the drums on the opposite side of their body.
- Have your child do “cross crawls” in an obstacle course or during activities at home. Instruct them to touch their right elbow or hand to their left knee and vice versa while walking forward or while on all fours on the ground.