Proprioception- The sixth sense
We have for a long time been taught that humans have the five senses of vision, hearing, taste, smell and touch. Aristotle (384-322 BC) is credited with this traditional classification.
Researchers are now stating that there are many more senses and some claim that it might be as many as 20 different senses. At the moment I would like to just add one more…the sixth sense, which is not about seeing and talking to dead people as in the movie.
The sixth sense is the sense of proprioception!
Out of all our senses the sense of proprioception is probably the one that has the greatest influence on the approach we chose and the results we achieve when training and rehabilitating individuals.
Proprioception (Latin meaning “one’s own” “sense”): provides sensory information about joint angle, muscle length and tension which is integrated in the brain to give information about the position of our bodies. This sense makes it possible to scratch your nose, change gears in the car and touch-type without looking. In a completely dark room proprioception let us know the position of our joints without having to turn the light on. Proprioception is achieved via a system of sensory receptors including Golgi-Tendons (muscle tension) and Muscle-spindles (muscle length).
Proprioception allows us to learn new motor skills, it is a key component in muscle memory and hand-eye coordination and training can vastly improve this sense.
To ensure movements are fast, precise and co-ordinated the nervous system must constantly receive sensory information to be able to adjust and correct movements. The nervous system achieves this mainly through the cerebellum, which receives sensory information about positions of the joints and body from the proprioceptors.
It is a common mistake to assume that everybody has the same level of proprioceptive ability.
Disordered sensory integration and motor learning
There are many names describing dysfunctions of integration of the sensory and motor systems: Motor skills disorder, Movement Clumsiness, Developmental Dyspraxia, Poorly Coordinated, Minimal Brain Dysfunction, Physical Awkwardness, Sensory Integration Dysfunction, and Developmental Coordination Disorder. The World Health Organisation currently list Developmental Dyspraxia as “Specific Developmental Disorder of Motor Function”.
Epidemiology: In the USA 4-6% of children at school age struggle with motor difficulties to the degree that it causes concern to them and those around them. In 1998 Kadesjö and Gillberg found that motor coordination disorder frequently coexisted with poor attention span and concentration in about 6% of children. A study in Singapore showed that 4% of children in the ages 6-9yrs had motor coordination difficulties. Conservative estimates suggest that 5% of children have sensory-motor dysfunctions worldwide and an additional 10% may have a minor form of the problem.
In 1996 Fox and Lent found that in contrast to the common belief that children grow out of these difficulties, they tend to linger without intervention. Early intervention is beneficial while the brain is changing dramatically during the first year of life and new connections and abilities are acquired. Delayed milestones (crawling, sitting, and walking), asymmetrical development, and regression of motor skills are signs of possible dysfunctions developing.
Dysfunctions may affect:
- Muscle tone- hypotonic ( floppy) or hypertonic (stiff robot like)
- Gross motor skills- posture, walking, running and jumping
- Fine motor skills- movement of small joints and muscles.
- Muscle strength – either weak or too brusque in their movements
- Motor planning- sequencing and speed of movement. Coordination of movements.
Signs of sensory/motor dysfunctions vary from person to person and can include:
- Poor balance
- Poor timing of movements
- Difficulty combining movements into a controlled sequence
- Difficulty remembering the next movement in a sequence
- Problem with proprioception – spatial body awareness
- Problems picking up or holding objects due to poor muscle tone and/or proprioception
- Clumsy- knocking things over or bumping in to people accidentally.
- Difficulty determining left from right
- Trouble determining distances between themselves and other objects
- Inability to relax
- Inability to isolate movements
- Difficulty repeating movements
- Low muscle strength and endurance
- Over sensitive to touch, light, sound and other sensory inputs.
- Difficulties with postural stability
- Difficulty grading movement and knowing how much pressure is needed.
Training and Proprioception -
Training can improve the proprioceptive system. It is important to assess the individual’s proprioceptive ability and motor control skills prior to structuring an exercise plan. Their ability will affect how quickly the individual will be able to change faulty patterns and improve the control of the different exercises. Good control will allow the person to follow your instructions better, and they will be able to feel the difference between right and wrong. Individuals with poor control will be very slow in adapting and they require a lot more instructions and supervision. Some people cannot feel what position they are in and have very little ability to perform isolated movements of specific joints.
Testing of proprioceptive system (and overlapping senses):
- Observation of muscle tone in sitting and standing gives clues of the ability to sustain a position against gravity
- Motor sequencing- touching the thumb against the other fingers of the hand in sequence one after the other at a certain speed. Observe the errors in sequence and examine both hands. When attempting fine motor skills, affected individuals often show signs like grimacing or sticking the tongue out.
- Nose-finger test to evaluate proprioception and fine motor coordination.
- Moving a limb against resistance to evaluate strength. Also look for additional movement to evaluate the ability to isolate (stabilize) a joint.
- Sustained testing- evaluate energy consumption in a movement. Some individuals will quickly fatigue and are unable to maintain energy wasting activities. Fatigue often affects proprioception.
- Isolated movement- single joint and eye movement can easily be evaluated.
- The ability to relax- examiner holds the individuals arm, instructs them to fully relax and lets go of the arm. If able to relax the arm should drop down.
- Ability to detect an externally imposed passive movement. Assess whether the individual can detect passive movements of a joint with their eyes closed.
- Ability to re-position a joint to a predetermined position.
Once the proprioceptive ability has been evaluated a program can be designed. Proprioceptive difficulties should be addressed immediately. Perfect form, good range of movement and adequate stabilization are all dependent upon proprioception. Working on specific stabilization patterns and isolated joint movements are good home exercises for patient and trainees. Proprioceptive awareness has to be trained very frequently to vastly improve.
When instructing an exercise program it is important to:
- Aim for perfect quality of movements- poor form will not improve automatically instead we develop a fixed dysfunctional pattern.
- Start with slow precise movements without loading
- Focus on the movement
- Use mirrors to demonstrate and monitor correct movements
- Perform the movements with closed eyes – feel the movement
- Be able to distinguish right from wrong in movements- “Show me right, show me wrong”
- Remember that the sensory and muscular systems are trained simultaneously- brain training
- Never exceed the loading the stabilization system can manage.
- Train the same movement in different postural positions
When first learning an exercise the movement is often slow, stiff and easily disrupted. With practice the execution becomes smoother and almost automatic. This process is often referred to as muscle memory and motor-learning. Evidence has shown that increases in strength occur well before muscle hypertrophy does. Strength training enhances proprioception and motor-neuron excitability which improves communication between the nervous system and the muscles themselves. This confirms that muscle strength is initially influenced by the inner neural circuitry, rather than by physiological changes in the muscle size.