This is the third in a series of articles about the kinds of skills addressed by occupational therapists working with children. This article will focus on bilateral integration which refers to the ability to use the two sides of the body (and the brain) together effectively to execute skilled and precise actions. A child who has poor bilateral integration will likely have trouble with self-care tasks such as buttoning, zipping, putting toothpaste on a toothbrush, tying shoes, using scissors, or writing. Sports skills such as throwing and catching or hitting a ball with a tennis racket or golf clubs, may also be difficult for the child with poor bilateral integration skills.
When thinking of the concept of “sides” in relation to movement, most people are familiar with the fact that humans have a dominant hand. This is the more skilled hand which usually will do the harder job when a task requires both hands working together. In order to open a jar, one hand is used to stabilize the jar (the non-dominant hand) and the other hand removes the lid (the dominant, more skilled and more powerful hand). The dominant hand will usually be the hand with which a person writes, throws a ball, holds tools, and threads a needle. However, it is not uncommon, and not necessarily pathological, for a person to do some things with the right leading and others with the left.
In the developmental sequence of motor skills, a child begins using both hands by engaging in symmetrical acts (using both hands to do the same action), such as when a 3- or 4-month old infant reaches up into the air with both hands at the same time. As the child develops, the movements will begin to be more asymmetrical. The child first gains the ability to control one hand at a time and then to have one hand do one task while the other hand is doing something different. An example of this is when a child learns to zip. One hand must hold the bottom of the zipper down, while the other hand pulls the zipper up. Many self-care skills require this type of asymmetrical coordination. Another important step is mastery of rhythmic reciprocal movements such as the movement used to pedal a bike, where the legs are doing the same movement at different times, maintaining a consistent rhythm.
Before the age of 4 or 5, we would not expect to see a child have a strong dominant hand although some do show an early preference for one hand over the other. Most children will learn tasks first on one side, then on the other. For example, a baby will begin creeping up steps, with the same knee leading every time. It may be the left or the right, but initially, every time the child wants to go up to the next step, she will place the same knee up and pull the other side up second, in a pattern that repeats. Eventually, the child will be comfortable with this action and she will then begin using the other knee as the lead knee every time. Finally, after she is quite comfortable with this, she may begin alternating knees as she creeps up the steps on her knees. This sequence of learning a task on one side and then on the other before moving on to learn the next more complicated task is very important for children. So, for a period of time, it is typical that the child seems to switch dominant sides quite frequently.
Looking at how babies learn to crawl is a great way to understand the broader implications of these issues of “sidedness”, which is also called laterality. The baby begins by lifting the head when placed on his stomach. Eventually, he will push up onto his elbows and hands, then back onto his knees. He may spend several weeks, going back and forth from lying on his stomach to getting up onto his hands and knees. This is a very symmetrical movement, with little rotation in the trunk. Then he may spend another period of time a few weeks perhaps, rocking back onto his knees and forward onto his hands. These activities are building muscles in the baby’s trunk, hips, shoulders, arms, and hands. Yet, up to this point, everything is symmetrical, and the parts of the body are moving together. The baby will be focusing on either the upper body lifting off the floor, the lower body lifting off the floor, or getting the whole trunk up off the floor into an all-fours position.
The next part is where things get interesting, because the baby must shift his weight sideways in order to be able to pick up one knee and move it forward to actually crawl forward. So now it’s become a 3-dimensional movement, not just forward/back and up/down that the baby is dealing with, but also side to side. Furthermore, while one knee moves forward, it is the opposite hand that will reach forward, requiring bilateral integration.
Using the two sides of the body together in a coordinated fashion requires the two sides of the brain to work together as well. The left side of the brain controls the right side of the body and the right side of the brain controls the left side of the body. So, to carry out an alternating pattern, like crawling, there is continuous communication back and forth between the two sides (hemispheres) of the brain as the two-sided movement is organized and sequenced. As the baby practices this motor task, his brain is developing new motor pathways and making more connections. This is one of many reasons why crawling is such an important developmental milestone which should not be skipped.
Transitional movements are also extremely important in the development of good bilateral integration. These are the movements a child uses to get from one position to another. For example, getting from a seated position to hands and knees, or from hands and knees to seated position. Transitional movements involve asymmetrical weight bearing through the body and rotation in the trunk. This means more weight on one hip than the other, or there may be no weight on one hip and all the child’s weight is on the other hip. This requires the brain to integrate its two sides-requiring enhanced communication between the two hemispheres. In addition, as the child engages in these transitional movements, the core (or central) trunk muscles which are used to carry out the movement, are developing and the child is building a stronger center.
Some signs that your child may be having difficulty with bilateral integration are described below:
- A child with strong hand dominance before the age of 4 or 5, who uses one side to the exclusion of the other.
- A child with no strong hand dominance after the age of 5.
- Difficulty learning tasks that require the coordinated use of the two hands together, such as tying shoes, buttoning buttons, or cutting with scissors.
- A child who avoids crossing his or her midline. This can be seen when a child shifts her weight or turns her trunk in the chair, so she will not have to reach across her center to get something on the other side of the table. She may always use the hand that is closest to the object she wants and avoid reaching across her body to get things.
- An older child (6 years old or more) who does not start on the left and work towards the right side of the paper (use a left to right progression) when doing math problems or writing. For example, the child may work from the right side to the left or have a very haphazard approach to doing a page full of math problems.
If you see any of these signs in your child, or if you suspect that your child is having difficulty with bilateral coordination, an OT can help. By doing an evaluation, the OT will be able to clarify what the problem is and make recommendations for how it should be addressed.