Do you ever wonder why that ankle never felt the same after you sprained it?

Have you ever walked through a doorway and suddenly be surprised when you hit your left shoulder on the doorframe?

All this has to do with an internal map of your body, also known as your Body Schema.

In a previous article written by one of our resident physiotherapists, Cat Kajary: “Use it or Lose it: Boost Body Awareness in Your Pilates Clients”, she talks about the concept of proprioception (the ability of your brain to understand and use sensory input coming from a number of internal stimuli), how proprioception works, its relation to body awareness, and why it is important to our clients.

In this article, we are taking things one step further and talk about how our senses shape the internal model of ourselves, i.e. body schema. Some may think of senses as separate channels of information, but they actually work together to give us a reliable picture of the world. Your senses integrate to form a complete understanding of who you are, where you are, and what is happening around you, thus making it possible for us to interact effectively with our environment and experience the world.

The senses that have a major impact on your body schema are the somatosensory, vestibular, and (to a lesser degree) visual senses:

A. Somatosensation (touch and proprioception)

One of the ways (and the most important with respect to Pilates and other movement disciplines) we sense our environment is through a variety of sensory receptors that respond to and transmit information related to the body, aka somatosensation. For more discussion on these sensory receptors, you can review “Use it or Lose it: Boost Body Awareness in Your Pilates Clients”.

Somatosensation is a collective term for the sensations of touch, temperature, body position, muscle stretch and/or contraction, proprioception, and pain that is recognized through sensory receptors in the skin, muscles and certain internal organs.

i. Somatosensory receptors in the skin (deep and superficial layers)

A wide assortment of sensory receptors live in the deep and superficial layers of the skin that respond to various kinds of stimuli such as pressure, light touch, texture, vibration, tissue stretch, tissue relaxation, pain, and temperature. These receptors send information to the brain about where we have been touched, how much pressure was applied, and whether the skin was injured.

ii. Somatosensory receptors in muscles, fascia, and tendons

Sensory receptors in muscles, tendons, and fascia receive and give information that tell the brain how fast, how much, in what direction, and when a muscle is stretching and/or contracting. They also tell the brain about any mechanical pressure, deformation, vibration, or pain that is occurring in a muscle.

iii. Somatosensory receptors in joint capsules, ligaments and spinal discs

A variety of sensory receptors reside in the joint capsules, ligaments and spinal discs that lie between the bones of the vertebral column. They respond to various kinds of stimuli such as compression, vibration, tissue stretch, tissue relaxation, and pain. These receptors send information to the brain about the static position of joints, joint movement, how much pressure was applied, and whether your joint is in an “unsafe” zone of movement.

The richest sources of somatosensory information are the feet, hands, vertebral column and pelvis (and also the face, tongue, and lips). Have you ever wondered why we feel lighter on our feet and perhaps they feel “wider” on the ground after massaging them on a weighted ball or other small object? Exercises that stimulate the somatosensory receptors in the soles of the feet as well as the joints in the feet and ankle inform the brain that something is happening down there, which causes the brain to “pay more attention” to the feet and turn on motor strategies related to standing on the feet.

B. The Vestibular Sense (“Balance”)

The vestibular sense is our equilibrium and balance center. It is an unconscious sense in that we are completely unaware of it, if it is working well for us. The vestibular sense tells us about changes in position and movement and helps us maintain our balance.

The vestibular sensory receptors originate in the inner ear, which contain hair cells encased in fluid. These receptors function like a carpenter’s level. When you move your head or trunk, the hair cells move and send input to the nervous system telling it that the head has moved. In this way, the inner ear tells us about where and how fast we are moving in space. It also tells us whether the head is straight, rotated or tilted with respect to gravity.

It helps us to maintain our posture and balance by turning on antigravity muscles in the trunk, lower limbs and shoulder girdle. If you tilt your head down to look at something on the floor, your vestibular sense would tell your brain that your back muscles need to turn on so that you don’t fall flat on your face.

The vestibular sense also has a direct effect on eye contact and gaze stabilization because it has direct connections to the nerves that supply the muscles around the eyes.

Exercises that include head tilting, head rotation, trunk side flexion, trunk rotation or balancing in unstable positions really makes use of your vestibular sense.

C. Vision

While all the senses are important, we tend to rely the most on sight because visual information is one of the most reliable and accurate sensory modalities. Visual stimuli are recorded directly onto the retina, a sensory receptor. The brain devotes more space to processing and storing visual information than all other senses combined. In all, about 30 cortical areas participate in visual processing.

Vision works closely with our vestibular sense to maintain our visual gaze and head stabilization.

On the other hand, vision can dominate our perception of the world around us and overcompensate for movement strategies and maintaining balance. Our eyes can pull us forward in space, such as when we find ourselves hunched over when looking at a computer screen for too long.

Having clients “soften” their gaze while balancing helps to get them to pay more attention to their somatosensation and vestibular senses. You can condition the visual/vestibular relationship by having clients move their eyes while keeping the head stable and vice versa, especially in standing balance positions.

Learn more!

Next week I’ll explore how integrating these senses helps us understand our physical surroundings and why it’s important.

If you’re interested in learning more about how we apply the nervous system like I’ve described above to our movement sessions at Body Harmonics, join me in Neurophysiology 101 on Apr 16 & 17.