Aging

Global context of aging

we are living in an aging population

NZ context for aging

aging population, can be due to advances in

• medicine

• technology

• diet

• lifestyles

health conditions in older adults

aging population leads to a higher population of elderly suffering from health conditions.

age related changes associated with physical functioning

• musculoskeletal system

• neuromuscular system

• somatosensory system

• cardiovascular system

multi-sensory deficit = impairment in all sensory systems. compensation for loss of one sense is not possible, affecting postural control

musculoskeletal system and aging

• maximum muscle strength is achieved between 20-30 years of age

as we age:

• muscle cross sectional area DECREASES

• motor units decline and fibres atrophy

• At ~70 years of age: 30% decline in muscle strength.

Sarcopenia =

a progressive and generalised disorder of skeletal muscle strength, function and mass, that is most commonly associated with the normal aging process

causes =

• endocrine

• neurodegenerative disease i.e. motor neuron loss

• sub-optimal nutrition malabsorption

• age

• disuse

• cachexia (metabolic problem) / wasting.

outcomes of sarcopenia =

• decreased muscle mass

• increased fatigue

• decreased physical activity —> lower muscle mass —> sarcopenia (cycle)

muscle performance and aging.

muscle strength and endurance

• strength more affected than endurance

• reduction in muscle mass is greater in lower limb than upper limb

• concentric contraction more affected than eccentric contraction

• motor unit muscle fibres atrophy

• loss of appetite contribute to muscle loss

muscle strength vs muscle power

• muscle strength is a product of force

• muscle power is a product of force + velocity

• everyday activities requires POWER

joint flexibility and aging

• connective tissue becomes more rigid with age, affecting …

  • joint flexibility and ROM

  • posture

BUT
physical activity improves flexibility in individuals of all ages.

Importance of physical activity.

• improve muscle retainability

• use it or lose it

• prevents muscle loss

• retain muscle mass

9-12 months of training also increases VO2 max by 19% in men and 22% in women.

neuromuscular system and aging.

decline in …

• number of spinal cord axons

• nerve conduction velocity

• stimulus detection

• information processing

Impaired posture control …

muscle weakness + impaired timing in nerve conduction —→ impairment in muscle synergies —→ limited ability to adapt to perturbations in task and environmental demands. Hard to react to unexpected environmental changes.

Age associated changes in gait

• shorter duration of single-limb stance

• greater relative duration of double support

• wide base of support —→ improve balance

• reduced/limited “toe off” phase

• increased co-activation of muscles —→ increase joint stiffness = increase balance

• decreased gait velocity

• reduced push off = decreased stride length

• increase step width

• flatter foot landing.

somatosensory system and aging

• decreased quantity and quality of touch and pressure receptors

• decline in sensory fibres innervating peripheral receptors

• tactile sensitivity decreases

• vibration sensation threshold increases in the Lower Limb

Less ability to perceive stimuli = need greater stimulus for sensation = greater difficulty responding to small changes. Body relies heavier on visual and vestibular systems, but declines with age.

vision and aging.

• structural change in the eye —→ less light transmitted to retina

loss of:

• visual field

• visual acuity

• visual contrast sensitivity

closely related to falls

changes to surface = difficult to see contrast

elderly have difficulty navigating, seeing at night, judging surfaces.

vestibular system and aging

• input from visual and somatosensory systems is compared to and calibrated by the vestibular system

• responsible for the amplitude of automatic postural adjustments

• 40% loss of the vestibular hair and nerve cells by the age of 70

CV system and aging

• VO2 max declines at a non-linear rate

• after 45 years, the decline rate is larger

• by 60 years, it averages below 11% for men and 15% for women.