| A | B |
|---|
| the ideal standing posture is one in which the line of gravity runs: | through the mastoid process, just in front of the shoulder joint, just behind the hip joint, just in front of the center of the knee joint, in front of the ankle joint |
| muscles active in standing | soleus, iliopsoas, gluteus medius, tensor fascia lata, erector spinae |
| role of soleus in standing | is continuously active bc gravity tends to pull the body toward the feet |
| iliopsoas and standing | remains contantly active |
| gluteus medius and tensor fascia lata and standing | are active to counteract lateral postural sway |
| erector spinae muscle and standing | are active to counteract gravity's tendency to pull the trunk forward |
| lordosis | an increase in the anterior lumbar curve |
| kyphosis | an increase in the posterior thoracic curve |
| scoliosis | lateral curvature |
| muscular and skeletal changes with age | 40% decrease in strength between 30-80 yrs, decrease in range of motion, more co-contraction, larger motor units |
| sensory age related changes | vision-lens elasticity and corneal opacities, somatosensory--vibration and tactile thresholds higher, vestibular--40% loss in hair cells by 70 yrs |
| three bodily sensory systems for detecting and maintaining balance | visual system, vestibular system, and proprioceptive system. work together to determine the body's location, surroundings, orientation, currrent movement, limb position and overall stability. |
| role of CNS in balance | monitors the sensors and initiates required involuntary adjustments, or reflexes via the motor control systems |
| visual systems role in balance | used to detect obstacles, predict slippery or dangerous surfaces where extra caution should be exercised, detect changes in walking surface level or slop, and provide a measns to plan a safe rout of travel. can also be used to determine distance using depth perception, speed, position, height, orientation of both the viewer and any objects within their field of view |
| vestibular system and balance | is responsible for detecting orientation and movement of the head, and as such provides the basic sense of balance. as well as providing a sense of balance stablizes the eyes during movemnt of the body and/or head through the VOR reflex. Failure of this system would result in constantly changing field of view, hindering vision and therefore balance |
| ankle strategy | is used to correct small discrepancies in balance. The feet remain planted and the body moves about the ankle joints like a pendulum to realign the COG and BOS. Ankle strategy corrections generally occur in flexors and muscles starting at the feet and moving upwards towards the trunk. |
| hip strategy | performs the same realignment tasks as ankle strategy, but on a larger scale. Hip strategy is commonly used where the BOS is reduced, for example when one foot is in front of the other, as if walking on a beam. As opposed to ankle strategy, the order of muscle reactions starts at the trunk and moves down to the knee and ankles. |
| stepping strategy | is used for large corrections where the COG's downwards vector ground intersection point moves outside the BOS. This usually involves a corrective step, stumbling or hopping. This response is actually very similar to normal controlled walking, as the when moving forward, the COG moves outside the BOS and a forward step is taken. This activity can be easily detected through sudden drops in foot-strike to foot-strike timing intervals and abnormalities in the gait cycle |
