Chapter 10: Neuromuscular and Movement Function: Muscle, Bone, and Joints
I.
II.
Introduction
Neuromusculoskeletal and Movement Function in Older Adults
a. Various tissues make up the neuromusculoskeletal system, including muscle, tendon,
ligament, bone, cartilage, and nerves
b. Age-related body structure and function changes are prevalent in the
neuromusculoskeletal system
i. Some of the most salient age-related changes in the neuromusculoskeletal
system include
1. Decreased muscle strength and power
2. Marked loss of skeletal muscle mass
3. Decreased number of functional motor units
4. Decreased percentage of Type II (fast twitch) fibers
5. Changes in postural alignment
6. Bone and cartilage changes
7. Changes in balance and gait
8. Decreased maximal speed of movement and initiation of responses
9. Increased threshold for vibration sensation and decreased
proprioception
ii. Physical changes
1. Physically fit
a. may still work in their chosen occupation, may participate
in activities with individuals younger than themselves, and
continue to exercise on a regular basis for their health and
well-being.
2. Physically independent
a. individuals whose physical function status allows them to
participate in advanced activities of daily living (ADL) and
who continue to be active in hobbies and leisure and social
activities.
3. Physically frail
a. perform ADL but may have a debilitating condition or
disease that is physically challenging daily
b. can live independently with human or environmental
assistance but may be unable to engage in certain
instrumental ADL (IADL).
4. Physically dependent
a. cannot perform some or all basic ADL (BADL) because of
acute or chronic conditions, cognitive problems, or
personal factors, such as physical inactivity, smokingrelated impairments, or increased weight
c. Age-related changes in Muscle strength and Power
i. Isometric strength
1. can change insignificantly until about the sixth decade but then
decreases from 50 to 70 years of age and about 3 percent thereafter
ii. Concentric strength
1. decreases in a pattern similar to isometric strength, with the most
dramatic losses after 70 years of age
2. upper extremity muscles tend to demonstrate less decline than the
lower extremity muscles
iii. Eccentric strength
1. declines are not as dramatic as concentric strength changes
iv. Dynamic strength
1. changes over time in functional muscle groups
2. the maximum torque that can be generated through a specific joint
ROM
v. Muscle power
1. the ability to generate force rapidly
d. Sarcopenia and Age-related Changes in Muscle Structure
i. Sarcopenia
1. one of the main determinants of musculoskeletal impairments
2. reduced function in older adults
ii. Sarcopenia
1. the age-associated loss of skeletal muscle mass and function
iii. Slow-twitch fibers (type I)
1. contract very slowly
2. fatigue resistant
3. are recruited when muscle contractions must be maintained for
long periods
iv. Fast-twitch fibers (type II)
1. contract very rapidly and develop high tension, although this
tension can only be sustained for short periods
e. Age-related Muscle Changes and Function
i. 13 percent of men aged 65 to 74 years and 40 percent aged 85 years and
older are unable to perform at least one of the following activities
1. lift a 10-pound weight
2. stoop or kneel down
3. reach overhead
4. write or grasp small objects
5. or walk two to three blocks
ii. Among women
1. 19 percent of those aged 65 to 74 years and 53 percent of those
aged 85 years and older are unable to perform at least one of these
activities
f.
g.
h.
i.
iii. Muscle power may be even more influential than muscle strength on an
older adult’s mobility, physical function, and functional performance
Age-related Changes in The Skeletal System
i. The skeletal system functions to:
1. provide a stable framework that enables muscle contractions to
generate force and movement
2. protect soft tissues and vital organs
3. serve as a reservoir for calcium homeostasis and a site for red
blood cell production
Changes in Bone
i. Peak bone mass (PBM) is achieved during young adulthood
1. after the third decade, bone mass declines
2. Initially the rate of bone loss is slow and similar for men and
premenopausal women.
ii. bone remodeling.
1. the adult skeleton repairs and adapts
iii. The major types of bone cells activated in a coordinated fashion within
each remodeling unit
1. osteocytes, cells embedded in mineralized bone that direct
remodeling when fatigue damage and changes in the mechanical
environment are detected
2. Osteoblasts
a. cells responsible for bone formation
3. Osteoclasts
a. cells responsible for bone resorption
4. Modeling
a. the process responsible for bone shape
b. is less active during the second half of life
Changes in Cartilage, Joints, and Tendons
i. Age-related changes in cartilage, tendons, and joints are associated with
alterations in collagen and elastin extensibility and decreases in various
proteins found in cartilage
ii. Connective tissue is found nearly everywhere in the body
iii. all types of connective tissue have similar features
iv. Collagen
1. basic protein component in fibrous connective tissue found in
bone, tendon, ligaments, and cartilage
v. Collagen fibers are arranged in crisscrossing bundles that are chemically
linked to form structure in the body and are strong and flexible in the
younger years
Age-related Changes in the nervous system
i. Biochemical and morphological changes in the neurons and receptors
ii. Loss of neurons
iii.
iv.
v.
vi.
vii.
viii.
ix.
x.
xi.
xii.
xiii.
III.
IV.
Defects in neuronal transport mechanisms
Decreases in myelin reducing the conduction velocity of nerves
Defects in protein synthesis
Cumulative trauma
Oxidative stress and vascular changes
Cerebral atrophy
Increased cerebrospinal fluid space
Specific neuronal loss
Reduced dendritic branching
Increased lipofuscin granules
Decreased effectiveness of neurotransmitter systems; selectively reduced
activities in dopaminergic, cholinergic, and noradrenergic systems
xiv. Reduced cerebral blood flow
xv. Diminished glucose utilization
xvi. Alterations in electroencephalogram
xvii. Loss of motor nerve fibers
xviii. Decreased number and size of motor units
xix. Slowing of nerve conduction velocities
xx. Increased plaques and neurofibrillary tangles in selective brain regions
Assessing the neuromusculoskeletal system in older adults
a. ROM and Flexibility Assessment
i. Comparison to standard norms is not appropriate unless the norms include
older groups because studies have found differences in ROM in older
subjects compared with younger subjects and differences in older adults
by age-groups
ii. Even if ROM is within normal limits for individuals of a particular age, if
greater ROM is required for, say, hobbies such as weaving or car repair, it
is the latter that has a greater impact on the individual’s quality of life
iii. Flexibility is a measure of the extent to which joint ROM is limited by the
extensibility of joint soft tissues as well as tendons and muscles
iv. Lower and upper extremity flexibility can be measured by the “sit-andreach test” (Nieman, 2003) and the “back-scratch test
b. Muscles Strength and Power assessment
i. Muscle strength can be assessed in clinical settings using various methods
including manual techniques, instrumentation, and functional activities
ii. One of the greatest advantages of isokinetic testing is that it can be used to
determine movement capability at different speeds and thus may be better
able to quantify age-related changes than manual muscle testing
iii. Assessing dynamic strength is important in older adults because common
ADL and activities (e.g., walking and rising from a chair) require speed
and the generation of power in addition to strength
Management of neuromusculoskeletal impairments in the older adult
a. Strength and Resistance Exercises
i. systematic strength training programs can improve skeletal muscle
strength in the older adult population, including the young- old and the
very-old
ii. Older adults who participate in strength-training research studies are
typically carefully screened for risk factors and exercise contraindications
iii. Isometric, isotonic, and isokinetic muscle strengthening programs, simple
active exercises using body weight as resistance, and walking and aerobic
exercise programs have been found to be successful at increasing U/E and
L/E strength in older men and women
b. Flexibility Exercises
i. Static
1. a position is assumed, held for a period of time, and then relaxed
ii. Ballistic
1. repetitive bouncing motions where the muscle is rapidly stretched
and immediately relaxed
iii. Proprioceptive neuromuscular facilitation
1. alternating isometric muscle contraction (hold-relax), alternating
isotonic muscle contraction (contract-relax) or passive stretching
through a series of movements
iv. Dynamic
1. the joint is moved through full ROM repetitively, such as with
dancing or tai chi