Download MUSCLE AND BONE HEALTH

Summer 2015
MUSCLE AND BONE HEALTH
INTRODUCTION
Age related alterations in musculoskeletal health
include a decline in muscle strength, muscle
mass, and bone mineral densitometry (BMD) and
bone strength. The decline in bone strength and
muscle loss are features of the aging process.
However these reductions in bone and muscle
health can potentially put people at risk of falls
and /or fractures, and ultimately result in an
increased risk of disability, loss of independence,
reduced quality of life and increased mortality.
Sarcopenia is the name given to the clinical
condition of pronounced declining muscle mass
and strength, which can affect both men and
women and is found to increase proportionally
with age.
Osteoporosis (and its precursor osteopenia) is the
skeletal condition characterized by compromised
bone strength and is associated with low bone
mineral density, bone tissue fragility and an
increased risk of fractures. Losses in bone and
muscle health can begin in the late 20’s however
accelerate in the 50’s.
Osteoporosis and sarcopenia share similar risk
factors and both impact directly and indirectly
on the risk of falls, fractures, reduced mobility
and quality of life. Evidence supports that these
risks may be lessened through healthy lifestyle
choices which include sufficient dietary intake of
protein, calcium, and vitamin D as well as
regular physical activity.
MUSCLE HEALTH
The loss of skeletal
muscle mass and to a
greater extent, skeletal
muscle strength and
power occurs with aging.
These changes in muscle
strength can lead to
deterioration in function
and adversely impacts on
activities of daily living, quality of life, bone health and the risks of
falls and ultimately fractures.
The decline in muscle mass,
strength and power begins in our 20’s, however it becomes more
pronounced around the age of 50 years. For females, the decline
in bone and muscle mass and strength occurs usually around the
time of menopause.
There are multiple factors associated with the changes in the
strength and quality of muscle and bone which include:
 Reduction in dietary protein
 Resistance of muscle protein synthesis to anabolic stimuli
 Low Vitamin D intake
 Reduction in physical activity
 Commencement of menopause in females
Dietary protein and muscle
protein synthesis
For the maintenance of
skeletal muscle, the body
needs to synthesize muscle
protein. This process also
contributes to the body’s
ongoing growth and repair.
The ingestion of protein and
amino acids (the building
blocks of tissue formation
within the body) as well as
physical activity stimulates
muscle protein synthesis. As we
age there is a tendency for
inadequate protein intake,
which is compounded by the
body’s resistance to muscle
protein synthesis.
To combat these two changes
we must consume more dietary
protein per day.
Dietary protein and muscle protein
synthesis (continued)
In addition, resistance training will stimulate and
increase muscle protein synthesis with the flow
on effect of improved muscle size and strength.
Exercise not only rebuilds muscle mass and
strength, but it also contributes to improving
functional capacity, performance and reduces the
risk of falls and has a positive effect on the
body’s immune system.
To compensate for
the
decline
in
muscle
protein
synthesis with aging
and
to
sustain
health
in
older
persons,
it
is
suggested
that
protein intake be
between 1 and 1.2
grams per kilogram
of body weight per
day. Adjacent is a
table which shows
the protein content
in some foods.
This recommendation remains within the
advocated protein intake of 10 to 35% of the
overall macronutrient consumption for adults.
Modifications to these levels and consultation
with a treating physician are recommended
where medical conditions such as inherited
metabolic disease or liver and kidney failure are
present. Higher protein ingestion in older adults
is also key to maintaining bone structure and the
competency of the body’s immune system.
Currently there is a trend that many young
individuals are not consuming even the lowest
recommended protein intake which then
escalates with aging.
The quality and type of protein you include in
your diet can also have an impact on muscle
protein synthesis and bone health. “High quality
proteins” such as fish, lean meat, dairy products
and eggs provide more muscle building amino
acids than “low quality proteins”. The more
amino acids available following a meal, the
greater the muscle protein synthesis occurs. The
distribution of protein intake throughout the day
is also essential. It has been proposed that the
ingestion of 20 to 25 mg of protein at each meal
is preferred than skewing protein intake to one
meal.
Older individuals tend to eat smaller meals and
are therefore at risk of decreased energy intake.
Supplementation is often a good solution, and
one which contains high levels of leucine is
recommended. Leucine is a potent and key
dietary anabolic amino acid capable of
stimulating muscle
protein synthesis at
an increased rate
following ingestion,
and is found in
many
protein
sources.
Milkderived
proteins
have been shown to
be
superior
for
promoting muscle
protein
synthesis
than
protein
derived from plant
sources.
There is substantial evidence to support the
rationale for protein supplementation prior,
during or within hours of resistance or aerobic
exercise and is a good option pre and post
exercise. Leucine supplementation is reported to
enhance recovery and repair of muscle damage
following training and can result in greater gains
in lean muscle mass and muscle cross sectional
area.
BONE HEALTH
There is growing evidence that bone mass and
strength is closely related to muscle function.
The close relationship is underpinned by the
concept that during forceful contractions of
muscles, the bones are exposed to increasing
loads which has a positive effect on bone mass,
size and strength.
Both features (low bone mass/strength and
diminishing muscle function/strength) can have a
significant impact of a person’s functional status,
increase their risk of falls, disability, loss of
independence and quality of life.
The accelerated loss of muscle mass and strength occurs at an
earlier age in women, usually around the time of menopause
and often can be associated with a decline in BMD. The
reduction in BMD is linked to a significant increase in the
prevalence of osteoporosis.
Osteoporosis is defined as a multifactorial progressive
skeletal disease characterized by reduced bone mass,
deterioration of bone tissue and disruption of bony
architecture.
These factors can compromise bone
strength and thus lead to bone fragility and a
consequence of this is an increased risk of fractures.
Osteoporosis affects over 220 million people worldwide
and currently there is no “cure” for this condition. Age is
the most important risk factor for osteoporosis and is
independent of the BMD.
Currently, the medical paradigm of treatment for
osteoporosis is less than ideal, as it is directed at
those patients who already have had fragility
bony fractures, or those with the lowest bone
density or have high risk factors. However, in
50% of women who sustain a fragility fracture
they are osteopenic and not osteoporotic. Falls
or minimal trauma are the major culprits for
fragility fractures so a feasible approach would
be to instigate methods to prevent falls and
address fracture-related risk factors, such as
improving bone density and balance as well as
addressing muscle wasting and strength.
Current national and international guidelines for
the management of osteoporosis is a combination
of weight-bearing and resistance training, with
challenging balance exercises to address the risk
factor of falls. The most successful exercise
program for improving bone strength incorporates
a diverse range of weight-bearing activities such
as skipping, jumping, dancing and hopping.
Resistance training and weight-bearing exercises
which include stability exercises for the trunk and
balance retraining result in significant
improvements in muscle strength, balance,
physical functioning and bone mineral density.
Exercise is a powerful intervention!
Preventing falls is imperative as around 90% of
osteoporotic fractures and in particular hip
fractures occur as a result of a fall. Group exercise
programs which include resistance and balance
training can reduce the rate of falls by 22%.
Aquatic exercises are not consistently found to
have an impact on BMD or balance, however does
contribute to an improvement in muscle strength.
The water’s buoyancy also reduces the stress and
impact on the joints and reduces the risk of
injury.
Adequate intake of Vitamin D and calcium is
essential for both the prevention and treatment
of osteoporosis. Calcium is crucial for building
and maintaining bones. Vitamin D plays a role in
calcium homeostasis and has skeletal and
muscular benefits. Sunshine is necessary for the
production of Vitamin D in the body and to assist
with the utilisation of calcium.
However
ultraviolet
radiation from
the sun is also
a major cause of
skin cancer. So a
balanced approach
to sun exposure is
needed to ensure
adequate Vitamin D
production,
whilst
minimising your risk of
skin cancer. The body’s
production of Vitamin D
is also enhanced by
exercise.
The current daily calcium requirement for both
men and women is between 1000 to 1300 mg per
day.
For further nutritional information here are some website links
(http://www.aihw.gov.au/) (http://www.nutritionaustralia.org/).
Foods which are rich in calcium include whole and skim milk, cheeses,
yoghurt, tinned salmon, nuts and seeds. It is possible to meet these
daily requirements by natural
food sources and without
increasing your fat intake.
However supplementation
may be required and this
should
be
done
in
consultation with your treating physician.
MENOPAUSE
The onset of menopause in women is associated with a natural
decline in oestrogen and bone mineral density (BMD) as well
as deterioration in muscle mass and strength. There can
be an increase in the risk of fractures in the classic sites
of vertebrae, distal forearm and proximal femur with
this decline in BMD. Hormone replacement therapy
(HRT) has been shown to reverse the loss in BMD
associated with menopause; however it needs to be
commenced before the age of 60 years or within 10
years of menopause. It can be an effective and
appropriate treatment for the
prevention of osteoporosis-related
MENOPAUSE
fractures in those women who are
“A mysterious time
at risk.
Consultation with the
about which
appropriate treating medical practitioner
sinister myths
is recommended. As stated before exercise in
continue to cling.”
the form of resistance is beneficial to counteract the decline
Germaine Greer
of muscle mass and strength associated with menopause.
K E Y P O IN T S

A decline in muscle mass and to a greater extent, muscle strength occurs with aging

Age-related skeletal muscle loss is thought to stem from inadequate nutrition. If optimal intake of protein
cannot be met under normal circumstances, supplementation should be considered

A deterioration in the muscle synthesis process is another contributing factor

Milk-derived proteins have been shown to be superior for promoting muscle protein synthesis, rather than
protein derived from plant sources

Vitamin D and calcium are key dietary components which contribute to bone and muscle health

Protein intake has a direct link to bone structure and immune competence

Primary prevention for musculoskeletal health include education and exercise

Bone gain and maintenance can occur with exercise programs targeting the spine and lower limbs

Exercises is important for fall prevention

Menopause is associated with a decline in bone mineral density as well as muscle mass and strength