PET4076 Exam 3 Chapter 6 Balance Posture and Locomotion Objective 1 To identify the ways in which the multiple systems in the body contribute to balance and mobility Balance Stability Limits and Mobility o Balance the process by which we control the body s center of mass COM with respect to the base of support BOS whether it is stationary or moving o Standing upright in space primary goal is to maintain COM within the confines of the BOS a static balance task o Walking learning through space or transferring the COM continuously moves beyond the BOS A new BOS must be established with each step taken Dynamic balance tasks o Maintaining a stable upright position also involves the active contraction of various muscle groups to control the position of the COM against the destabilizing forces of gravity o How far older adults are able to lean in any direction without having to change their BOS constitutes their stability limits o Nashner 1990 Estimated that for adults able to align their COM directly above their BOS during quiet standing Sway as far as 12 in a forward and backward direction and 16 laterally before it is necessary to take a step because the limits of their stability have been exceeded o Reduced or asymmetrical limits of stability LOS may be the result of Musculoskeletal abnormalities caused by weakness in the muscles of the ankle joint or reduced ROM about the ankles neurological trauma that adversely affects weight bearing or weight shifting in a particular direction e g stroke Parkinson s disease multiple sclerosis or a fear of falling The boundaries of the stability limits will also vary according to an individual s inherent biomechanical limitations the task being performed and the constraints of the environment o Mobility the ability to move independently and safely from one place to another o Adequate levels are required for many different types of activities that are performed during daily life o Includes transfers e g rising from a chair climbing or descending stairs walking or running and other types of recreational activities e g gardening sport or dancing Anticipatory and Reactive Postural Control o Anticipatory postural control to describe actions that can be planned in advance Needed to avoid obstacles in our path as we walk to the store or plan to open what appears to be a heavy door Assists us in adapting our gait pattern as we move b t diff types of surfaces e g firm to compliant or moving surfaces wide to narrow o Reactive postural control to describe situation that cannot be planned in advance of the action required Necessary when we have to respond quickly to an event that we did not expect Stepping in an unseen hole Being bumped in a crowd Postural Control Strategies 3 strategies used to control the amount of body sway in a forward or backward direction o 1 ANKLE surface Body moves as a single entity about ankle joints as force is exerted against the Moves the upper and lower body in the same direction in phase Due to the small muscle around ankle Generally used to control sway when we are standing upright in space or swaying slowly through a very small ROM Used subconsciously to restore balance following a small ROM o 2 HIP The activation of the largest hip muscles Used when the center of gravity COG must be moved more quickly back over the BOS as the speed or distance of the sway increases Move the upper body in a direction that is opposite to the lower body out of phase Important as the speed distance of bodys way increase or when we are standing on a surface that is narrower than the length of the feet o 3 STEP When the COG was displaced beyond an individual s maximum LOS or the speed of sway was so high that a hip strategy was not sufficient to maintain the COG within the stability limits At least one or more steps must be taken to establish a new BOS avoid a Maki and Mcllroy 1996 stepping actually appears to be the preferred strategy even when the perturbation is small and the individual is free to respond naturally Various combinations used Postural Control Strategies Limiting Factors o Ankle Strategy limiting factors Adequate ROM strength within the muscles surrounding the ankle joint are The surface below the feet must also be firm and broad The individual muscle in the feet have adequate sensation to be able to feel the Older adults experiencing a significant decline in sensation in the feet or ankles will find it particularly difficult to employ this strategy when the perturbation is small and the individual is free to respond naturally o Hip Strategy limiting factors fall needed surface Unlike the ankle strategy the ability to use a hip strategy to control postural sway is determined more by the amount of muscle strength and ROM available in the hip region as opposed to the ankle Any weakness in the adductor and abductor muscles will adversely affect lateral stability important when walking o Step Strategy limiting factors To establish a new BOS when the perceived or actual LOS are exceeded Affected by both the amount of lower limb strength available and the speed with which it can be generated for rapid initiation of the step i e muscle power Slowed central processing older adults Reduced somatosensation in the feet and below normal ROM how quickly the step is initiated length of the step or steps taken after a loss of balance Theoretical Framework of Balance and Mobility o Systems Theory contemporary approaches to study of human postural control multiple systems collaborate to control bodily orientation and locomotion Such as sensorimotor musculoskeletal cognitive individual s capability for achieving a particular goal directed action o Action is shaped by the interaction that occurs b t the individual the task and the environment o Balance related impairments e g muscle weakness reduced ROM sensory loss compromise an individual s ability to accomplish a single daily task such as rising from a chair or climbing and descending stairs o Added second task e g carrying a bag of groceries talking to someone at the same time further compromises action b c of the need to divide attention b t two tasks o The existing environmental conditions e g reduced lighting conditions the absence of handrails on the stairs fall risk o Compromised abilities in older adults Cease to perform certain daily tasks Cease participating in social activities that they think will place them at high risk for falling Self imposed restrictions on activity short term