SENSORY INTEGRATION AND SWIMMING

by Lana Whitehead

Since most of us are not used to thinking of the brain as the director of all activity in the body and mind, we will introduce you to a new way of looking at learning and behavior. This will help the reader to understand important aspects of learning that most people never consider. Our nervous systems are constantly being bombarded by sensations (like light, smell, pain, cold etc.) from our environment. The brain has to organize this sensory information for it to have meaning. Sensory integration is the process of organizing sensory inputs so that the brain produces a useful body response.  It’s the “traffic cop”, directing traffic through the nervous system so that sensory messages get to the right “relay stations” and “depots”.

Sensory integrative problems are not obvious, yet they are widespread among children throughout the world. We are not just dealing with 2 separate camps here: Typical vs. Dysfunctional. Most children sit somewhere in between on the Sensory Integrative Curve. Once you become aware of the process of sensory integration in a child, you can become a better swim teacher, better able to facilitate the skill development of a typical child and help a dysfunctional child face his challenges.

In order to adequately describe the sensory integrative process it is necessary to give the reader some background on the nervous system and its relationship to the environment and learning. We will begin with the basic unit of the nervous system, the neuron.  There are about 12 billion neurons in the average human being.  Each neuron consists of cell body and a fiber that divides into many branches and twig-like fibers.  Most fibers have thousands of twigs that allow connections to thousands of other neurons.  The branches and twigs of the neurons intertwine like the twigs in a dense forest, but with much greater complexity.  These neurons and their twig-like fibers are arranged in long thin bundles called nerve tracts that usually carry one type of sensory or motor impulse.  It has been estimated that in a single second, one impulse will spread through up to a million neurons in many different parts of the brain.  The flow of electrical impulses through this complicated network of neurons produces learning.

A newborn infant has most of the neurons he/she will ever have.  However, at birth he/she has very few interconnections or synapses between his /her neurons.  As a baby interacts with the world and parts of his/her body, the sensory and motor impulses flowing among his/her neurons cause the fibers to grow branches and twigs that reach out toward other neurons.  Each new interconnection adds new elements to an infant’s sensory perceptions and motor abilities.  The more neural interconnections a person has, the more capable he is of learning (Ayers, 1982).

Synapses are the places where neurons make these interconnections.  They are bridges that carry the impulses from one neuron to another.  These bridges are electrochemical connections between the twig-like branches off the cell body of the neuron.  Neurons interact through synapses.  The ability of a synapse to conduct neural impulses does change significantly as one continues to learn.  Changes in the conductivity of synapses are the basis for learning (Ayers1982). 

The more a muscle is used, the stronger it becomes, up to point.  If it is not used, it becomes weak.  Similarly, the more a synapse is used, the stronger and more useful it becomes.  As with muscles, the use of a synapse makes the synapse easier to use, thus the argument for consistent, meaningful, accurate practice.  Every time a neural message crosses a synapse, something happens to make it easier for other similar messages to cross that synapse in the future.   Every time a motor process is repeated, less energy is needed to carry out the process the next time.  This is what happens in thousands of millions of synapses at the same time when we practice a drill.  In other words, when the physical impulses of rolling into airplane (backfloat) passes over many synapses, the structure and chemistry of those synapses change so they can transmit those messages faster in the future.  The repeated use of  synapses gives those synapses a memory of the motor skill, making it easier to perform that skill each time it is practiced.  Eventually it becomes automatic.

            Meaningful practice organizes the sensory and motor inputs from the body into a clear-cut body percept or body map.  The repeated use of synapses for a particular motor skill creates a neural memory of that skill.  We have neural memories stored in our synapses for everything we know.  The body percept is a composite memory of every part of the body and all the movements those parts have performed.  The more variations of movement the body performs, the accurate the body maps will be, thus the argument for a greater variety of aquatic based activities and movements in the lesson.  For example, training each swimmer to execute 4 basic swim positions – XYI & Pencil, to rotate in pencil from back to front, to vertical float, to float and roll in a ball, to execute arrow and flagpole alone etc. will provide their bodies with varied neural memories to plan more aquatic movements, in the same way that we use a map to find directions.  The more accurate the maps, the greater the ability of the body to perform unfamiliar movements.  The move accurate the maps, the greater the ability of the body to sense how fast and how hard each muscle must work to accomplish a task.  Swim lessons should be accurate (creating accurate body maps) and varied (moving the body through different aquatic alignments) to be effective.

The primary task of our nervous system is to tell us about our body and our environment, and to produce and direct our actions and thoughts. Over 80% of this system is involved in processing or organizing sensory input. Each part of the body has sensory receiving organs or receptors that pick up energy from that body part.  Each receptor changes the energy into streams of electrical impulses that flow through sensory nerve fibers to the spinal cord and brain. This very complex sensory processing produces a message in the brain and the motor neurons then carry that message to the body.  Each muscle has many motor neurons and electrical impulses in the motor neurons that cause the muscle to contract.  Many muscle contractions must be combined to align the neck and waist in the water, to rotate the body for a breath, and to swing the arms out the water.  For these muscle contractions to be coordinated and effective, the activity in the brain must be well organized.  Sensory integration is the process of organizing sensory inputs so that the brain produces a useful body response.  Sensory integration sorts, orders, and eventually puts all of the individual sensory inputs together into a whole function (Ayers, 1982).   

            When the functions of the brain are whole and balanced, body movements are highly adaptive and learning is easy.  Although every child is born with this capacity, he must develop sensory integration by interacting with many things in his environment.  A child’s play activities such as swinging, jumping, twirling, somersaulting, rocking, bouncing, climbing etc. supply his nervous system with varied sensations.  Sensations are “food” or nourishment for the nervous system.  Every sensation is a form of information to aid the body in making an adaptive response.

Until about the age of seven the child’s brain is primarily a sensory processing machine. This means that his brain senses and gets meaning directly from sensations and his/her responses are more motor or muscular than mental.  During the sensory-motor development years (birth – 7), it is important to supply the child with a variety of play opportunities, motor activities and sensory stimulation especially swim lessons.  If the sensory-motor processes are well organized in the first seven years of life, the child will have an easier time learning mental, social and complex cognitive skills later on.

The three sensory systems are: Tactile, Vestibular and Proprioceptive. The Tactile Sense is the largest sensory system in the body and it plays a vital role in physical and mental behavior. Because the tactile system is the first sensory system to develop in womb, it is very important for the overall neural organization. Without a great deal of tactile stimulation of the body, the nervous system tends to become unbalanced.  The skin has many different kinds of receptors for receiving the tactile stimulations of touch, pressure, texture, heat or cold, and pain.  The nuclei in the brain stem then process this tactile input and send a message that something is touching the skin, and whether that something is painful, cold, hot, wet or scratchy.

The tactile sensory system is regulated primarily by brain stem and lower brain that seldom enters into our conscious awareness.  In general, the arousal centers in the primitive brain are designed to wake us up, calm us down and detect whether a stimulus is dangerous or frightening.  So, if the child feels frightened or does not feel safe in the water, he cannot learn swimming on the conscious level until his tactile system is receptive and calm.  Therefore, the beginning or fearful child will need many secure warm touches and reassuring hugs. Research has shown that a firm, loving touch slows the heart beat, lowers the blood pressure and reduces activity in the arousal centers.

When a child is introduced to the water, he needs to be taught to trust the sensations of buoyancy & organize them so that he is on friendly terms with the water. By putting the child in many different positions in the water, the child learns what he can do, what the water can do & he eventually comes to terms with buoyancy. Blowing bubbles, rocking and bouncing, splashing, jumping, somersaulting, bobbing, diving in the water, going to bottom with the teacher, pushing off the bottom, swimming through hoops, etc. will aid a child in becoming comfortable with his new environment. Many varied aquatic experiences doing the learn-to-swim process are essential in producing a confident, well-adapted swimmer.

            The Vestibular System is the “business center” of the nervous system.  It is the unifying system.  All other types of sensations are processed in reference to this basic vestibular information. Vestibular input seems to prime the entire nervous system to function effectively.  When the vestibular system does not function in a consistent and accurate way, the interpretations of other sensations will be inaccurate.

The Vestibular sense is controlled by the inner ear.  One type of receptor (calcium carbonate crystal attached to hair-like neurons) responds to the force of gravity and the other receptor (semicircular canals) to the sense of movement (acceleration and deceleration).  The combination of input from the gravity receptors and the semicircular canals is very precise and tells us exactly where we are in relationship to gravity, whether we are moving or still and how fast we are going and in what direction. Vestibular sensations are processed mostly in the vestibular nuclei and cerebellum.  The impulses going down the spinal cord interact with other sensory and motor impulses to help us with our posture, balance and movement.  The impulses going up to higher levels of the brain interact with tactile, proprioceptive, visual and auditory impulses to give us our perception of space and our position and orientation within that space. It forms the basic relationship of a person to gravity and the physical world. 

Because our relationship to gravity forms a basic reference to all our sensory experiences, balance or stabilization must be a first priority in training all swimmers.  The swimmer’s neck muscles must be aligned because every change in position of the head and neck stimulates the semicircular canals. This shift in position signals a change in acceleration and direction and pulls the calcium carbonate crystals away from their normal position in the ear, which affects balance. Swinging the arms, initiating an underwater dolphin kick, rotation at the center of mass etc. all provide a great deal of vestibular input to the cerebellum. Therefore, the swimmer’s performance platform must be balanced and stable, so that brain will receive accurate information as to where the body is in space, if it is moving, in what direction it is accelerating or decelerating and it’s relationship to gravity and buoyancy.

            The Proprioceptive sense refers to the sensory information caused by contraction and stretching of muscles and bending, straightening, pulling and compression of the joints between bones.  Sheaths that cover the bones also contain proprioceptors.  The sensations from the our body occur especially during movement; but they also occur while we are standing still. The muscles and joints constantly send information to the brain to tell us about our position in space and in the water.  Most proprioceptive input is processed in regions of the brain that do not produce conscious awareness and so we rarely notice the sensations of muscles and joints unless we are learning a skill or new movement.

Proprioception from the muscles and joints contributes to our body percept.

Without that information, we would not know where the parts of our body are or how they are moving.  During movement, proprioception updates our body percept so that the brain can plan the next movement correctly and then contract the right muscles at the right time.  Imagine trying to swim freestyle blindfolded.  How do you know where your arms are above the water, where your legs are under water, where your head is in relation to your shoulders etc?  You know these things because the proprioceptors from your muscles and joints give your brain an accurate body percept or map.  Without that information you would have to use trial and error each time you swam freestyle.  It would be crazy to attempt to compete in a freestyle race if your body could not remember how to swim when you entered the pool. 

We are usually not aware of proprioception unless we think about it; however, if it were not there, we would have a rough time doing anything.  How many times have you swum a lap without thinking about what you are doing?  You were guided by proprioceptive signals and neural memories of previous proprioceptive experience.  Thus our performance platform, aquatic alignment and stroke postures must be carefully practice and memorized.  If these neural memories are precise we will have an accurate base so our proprioceptors can update our brain with information so it can plan the next movement correctly and then the next movement and so on.