Centre of Gravity & Proprioception

Proprioception Agility , Balance and Coordination controlled by proprioceptors Proprioception is fundamental to correct performance – which requires good agility, balance and coordination Proprioception is the body’s ability to transmit position sense ( from receptors in body) , interpret the information and respond accordingly (unconsciously or consciously) Play an important role in posture control and movement Proprioception is what allows us to know what position our body is in with out looking at our body parts It is proprioception that gives us the agility to change direction , to maintain our balance and the coordination to produce the activity Proprioceptors are afferent nerves that receive and send impulses from stimuli in skin ,tendons , joints and muscles to the CNS

Receptors Cutaneous receptors – afferent receptors in the skin Joint receptors Afferent receptors that lie in the joint capsule and the ligaments of the joint Muscle spindles Stretch of the muscle Golgi tendon organs tension within muscle

CNS One afferent nerves have sent input to the CNS the body’s motor response is determined by the location with in the CNS that interprets the stimuli and initiates the efferent reaction Spinal cord Spinal reflex – simplest form – protection Joint under excessive stretch – sudden activation of muscle reflex flexion to reduce the load Brain Stem Primary proprioception centre – maintain positions or posture Cerebral cortex Highest level of the brain – here correct movement is learned – conscious becomes automatic

Balance Balance is fundamental to most activities – required for even simple activities – standing Balance must be restore following injury or re-injury may occur Balance influenced by vestibular , visual and proprioceptors Vestibular – inner ear -Semi circular canals vestibular –Occular reflex – allows eyes to remain steady when body is in motion Oculomotor - - vision providing feedback about the relative position of the body in space if not interpreted correctly – a good example – car that is stopped at light and car beside you moves forward you think you are moving back wards Skaters – visual fixation – focusing on one object to avoid getting dizzy Test – Rhomberg , stork .. Line walking ( eyes open , eyes closed ) Exercise begin basis and move to more complex

Centre of gravity Point in body around which weight is balance Harder to find in body because of its irregular shape Anatomically speaking around S2 Slightly higher in men than women CoG changes as body moves The lower the CoG the more stable

Line of gravity / base of support An imaginary line that runs vertically through the CoG Used to determine stability of an object Base of support is a two dimensional area between and including the objects ( person) point of contact Can change base of support – wider stance more stable , feet together easier to get pushed over Object is most stable when line of gravity falls with in base of support if this line falls outside of the base it is difficult to maintain balance

Coordination Coordination is the complex process by which a smooth pattern of activity is produced Several muscles involved and must provide accurate response in both timing and intensity to be coordinated Development – start with simple activities – with repetition Progressions simple to complex

Agility The ability to control the direction of the body or segment during rapid movement Required flexibility , strength , power , speed balance and coordination Agility highly advance skill – provides base for speed – however speed must be accompanied by coordination Tests – sports – lateral running , T – tests , figure 8’s, stop starts Exercises again should start simple and move to more complex and to be work or sport related

Regaining postural stability and balance Is both Static Dynamic Dynamic for example, walking, climbing stairs, etc

MOVEMENT STRATEGIES What are the 3 movement strategies that are used by the body to maintain the CoG within a stable base of support? 1. ankle 2. hip 3. stepping

MOVEMENT STRATEGIES When would each strategy be used? Ankle: when small, slow movements, close to CoG Hip: larger, quicker movements required. Also if CoG gets closer to LOS. Stepping: if CoG gets out of Limit Of Stability.

INJURY AND Proprioception Studies of the knee and ankle show that there is a decrease in proprioceptive feedback from damaged ligaments to the CNS (sensory/afferents). Therefore, there is a decreased reflex excitation of motor neurons (efferents) to the muscles responsible for preventing sway/controlling balance.

Proprioceptive Training Proprioception exercises should be a routine part of a rehab program Balance first – then coordination followed by agility Static then dynamic exercises Simple to complex Exercises must be safe, yet challenging Stress multiple planes of motion Incorporate a multi-sensory approach / distractions Progress to sport-specific Multiple planes of motion – flexion vs extension, adduction vs abduction Multisensory approach – eyes open vs eyes closed Begin with static, bilateral, stable. Progress to dynamic, unilateral, unstable. Various surfaces – wobble boards, pillow, trampoline, etc Sport specific exercises are always done last

BALANCE TRAINING static: CoG is maintained over fixed base of support on a stable surface. i.e. Rhomberg tests

2. semi-dynamic: 2 types (a) maintain CoG over fixed base of support while on moving surface or unstable surface (BAPS/Wobble board) (b) transfer CoG over a fixed base of support to areas within the LOS while standing on a stable surface (pick up pens)

BALANCE TRAINING 3. dynamic: CoG maintained within the LOS, while over a moving base of support on a stable surface. Requires a stepping strategy i.e. hopping, walking on a balance beam More into plymetics – hopping, climbing, jumping, up stairs, down stairs, etc Ex dynmaic test for basketball player – shuffle side to side on their own Functinal/sport specific – have the basketball player mimic the motions of the trainer

Balance Training 4. functional: same as dynamic, except also have sport specific tasks included. i.e. catching/throwing a ball while running.