CHAPTER 6Balance, Posture, and Locomotion1. Age-Associated Changes in the Systems Contributing to Balance and Mobility a. Inevitableb. Postural control is effected when multiple systems fall below threshold of functionc. Reduced ability to perceive quickly and accurately where the body is in space, which, in turn compromises performance in speed, accuracy, balance, strength and coordinationd. Reduced ability to quickly accommodate changing task and environmental demandse. Balance is controlled by sensory system which includes vision, somatosensation and vestibulari. Vision : reduced acuity, contrast sensitivity, depth perception and narrowing of visual field. Results in slower processing info, less efficient integration and possibly altered perception1. Related diseases include cataracts, glaucoma and macular degenerationa. Due to peripheral neuropathy (nerve damage)2. Wade study: moved walls and ceilings but kept the floor still to see if the elderly would lose balance. They increased postural sway proving their increased visual sensitivity. Ring and Sundermeier did this with previously fallen elders; they showed an even greater swayii. Somatosensation : partial to complete loss due to peripheral neuropathy1. Bruce: the sensitivity of skin receptors and pressure declines as do the number of sensory pathways2. Perret & Reglis: 2 to 10 fold increase in vibration threshold needed because of reduced ability to feel contact b/t floor and feet. This also included age related declines in both the number and sensitivity of muscle and joint receptors3. Reduced sensation- problem when rapid postural adjustments as a result of unexpected threat to balance occursiii. Vestibular : Begins at 30 with gradual decline in density of hair cells that serve as biological sensors of head motion1. By 70 vestibular (ear) hair and nerve cells decline as much as 40%2. Paigea. Vestibulo-ocular decrease (reflex eye movement) which makes it difficult to tell if the world is moving or they are. This can cause problems in crowds, traffic and stores because of complexvisual enviornments3. Sloanea. Dizziness is number 1 reason for 75 year old age group to go seephysicianf. Motor System Changesi. Loss of large motor neurons, decline in important neurotransmitters such as dopamine, and decline in nerve conduction velocityii. Spirduso 1. Chronometric measure (SRT and CRT, movement time and RT) reveals that action- planning phase is the most declinediii. Stelmach1. Reduced ability to inhibit inappropriate responsesiv. Loss of fast twitch motor units1. Erima. Declined motor unit firing and loss of anticipatory postural abilities lead to slower processing speeds and increases risk of fallingv. Results in longer movement execution timesvi. Decreases muscular strength, power and endurance1. Lindlea. 50-70, strength lowers by 30% and decreases even more by 80vii. Loss of muscle power is most important factor for response itmeg. Cognitive System : Affects 10% over 65 and 50% over 80i. Cognitive impairment: important intrinsic risk factor for falls. Which includes attention, memory and intelligenceii. Brown1. Dividing attention between tasks becomes harderiii. Brauer1. Ability to recover from unbalanced posture becomes harder2. After 2nd task, it became even more difficult to restore balanceiv. Contribute to postural instability and subsequent falls in balance impaired h. Gait: Gait speed is 20% sloweri. Decreased1. Velocity2. Step length3. Step frequency4. Stride length5. Swing phaseii. Increased1. Stance phase2. Time in double support2. Evaluating the Multiple Dimensions of Balance (static and dynamic balance)a. Standing upright in space requires you to maintain COM with the confines of BOS and can be tested by a static balance taskb. Walking, learning through space or transferring, requires continual changes in BOS because COM moves beyond BOS and can be tested by dynamic balance tasks3. Limiting factors of an individual’s maximal limits of stability (LOS)a. How far older adults are able to lean in any direction without changing their BOS constitutes their stability limitsb. 12˚ forward and backward and 16˚ laterally (Nashner)c. LOS can be caused by musculoskeletal abnormalities or reduced ROM at ankles or neurological traumai. Vary according to biomechanical limits, task being performed and constraints of environmentd. Postural control strategies of ankle, hip and steps are included as limiting factorsi. Ankle: Must have adequate ROM and strength, surface must be firm, and muscle must have adequate sensationii. Hip: Any weakness in the adductor and abductor muscles will adversely affect stability, especially when walkingiii. Step: Must be able to establish new BOS and effected by lower limb strength and the speed of the initiation step. Is slowed with age and has reduced somatosensation in feet and below normal ROM4. Risk factors associated with falls among older adultsa. Muscle weaknessb. History of fallsc. Gait deficitd. Balance deficite. Use of assistive devicef. Arthritisg. Impaired activities of daily livingh. Depressioni. Cognitive impairmentj. Over 305. Intervention strategies to reduce fall risk includesa. Long term exerciseb. Environmental modificationsc. Multi factorial risk assessmentsd. Health promotion and educatione. Medication withdrawalf. Hip protector garments (reduce fractures)g. Scan table 6.3 and 6.4 (FAB scale and BBS scale- both balance scales with dynamic and static tests)CHAPTER 9Health, Exercise, and Cognitive Function1. Studies by Spirdusoa. Age by physical activity cross sectional study of reaction time between young exercisers,young non-exercisers, old exercisers and old non-exercisersi. Old ex. were faster at simple and choice reaction time (SRT and CRT) than old non but didn’t differ from youngb. Did the only animal study on rats with Farrari. Young rats increased oxidative capacity after training but old sedentary didn’t even maintain their fastest RTc. Both support the fitness to cognition relationship2. The fractionated reaction timea. SRT and CRT of old exercisers were faster than non-exercisersi. Fractionation proved the reason was due to exercise difference in the premotor time(PMT)-Clarkson and MacRaeii. PMT for exercisers was 187 which non-exercisers was 247 so this increase also gave non-exercisers a larger movement time (MT). The contractile time (CT) wassimilar3. Study by Dustman et al.a. Only positive findings b/t fitness and intelligence (cognition)b.