KINESIOL 4SS3 Lecture Notes - Bone Density, Body Water, Muscle Tone

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Aging and Body Composition
Body Dimensions
(I) Height
On average females
are shorter than males. We
also see that females reach
their peak height sooner
than males ( 16-18 yrs old).
Males reach their peak
height at about 20 years of
age.
Females start loosing
height before males.
At age 60-70 yrs
women will lose height at a
more rapid rate than men
Men loose 4% their
height by the age of 70
Percent height loss is similar between males and females, however, women
start at a smaller base height => loos of height is greater
Menopause:
o Osteoporosis
Much more rapid decline of bone mineral density in women
because of menopause (loss of estrogen)
Small fractures in vertebrae because of decreased bone
mineral density
Over time vertebrae fractures accumulate into more forward
posture ( a hunch) these fractures are more likely to happen on
the anterior side of the vertebrae => leads to kyphosis
o Vertebral disc compression
Accumulation of gravity over time
Vertebral disks make up 20-30% of total length of the spine
o Other determinants of height
People tend to loose a little bit of their foot arch (loss of
strength of ligaments and muscles)
Start to loose muscle tone as you get older (muscles help us
stand up straight. Loss of muscle results in slumped posture)
Peak height determined by genetic and environmental factors
Living in the altitude more stress on the body ( muscle and
bone)
Change in hormonal level because of exercise=> has impact on
overall bone density
Disease
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(II) Wight
Females: gradual
increase in weight until
approximately 5th decade,
weight then plateaus for a
couple of decades, then
slowly start to decrease
Males: similar pattern
to females, but decline in
body weight starts a bit
sooner
o Late 30s-40s
are stable.
o Weight starts to
decline in late 40s
Females continue to
rise in body weight longer
and keep the same body
weight for longer.
Males plateau at about 40-50
Body weight decline due to:
o Decline in muscle mass
o Decline in bone mass
Unusual or sudden weight loss in elderly may reflect health problems
o Cancer
o Emotional health problems
(III) BMI
Gender difference
in when peak BMI
generally occurs
o Eg. Males
between 45-49yrs
o Eg. Females
between 60-70yrs
BMI has a complex
relationship with
mortality risk, depending
on age
Different health
risk associated with high
or low BMI’s
Initially males have increase in BMI and then decrease after 40-50 years of
age
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Females increase until about 60 and then decline
Females are keeping/gaining weight longer, but they are loosing height
sooner => raising their BMI number
BMI associated with the lowest risk of mortality is going to change with age
High BMI => CVD, diabetes, hypertension
Low BMI=> osteoporosis (linked to frailty and risk of fractures => especially
for women) respiratory and GI illness
Typical range
for young individuals
is 18.5-25
As you age
BMI associated with
lowest risk of
mortality increases
Body Composition
2 main compartment:
o fat mass and fat-free mass ( muscle, bone, water)
o body composition is influenced by genetics and environment
(I) Total Body Water
Approximately 60-65% of body composition is water 9depends on
percentage of body fat)
Percent body fat dictates how much water your body holds
o Fat is hydrophobic
o Do not store water in fat
o Only about 20% of fat is water
o 70% of muscle is water
o if you have more fat-free mass you have more water
Body water decreases linearly
with age
Result => increase in dehydration
Newborns loose water very
quickly
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Document Summary

On average females are shorter than males. We also see that females reach their peak height sooner than males ( 16-18 yrs old). Males reach their peak height at about 20 years of age. At age 60-70 yrs women will lose height at a more rapid rate than men. Men loose 4% their height by the age of 70. Percent height loss is similar between males and females, however, women start at a smaller base height => loos of height is greater. Much more rapid decline of bone mineral density in women because of menopause (loss of estrogen) Small fractures in vertebrae because of decreased bone mineral density. Over time vertebrae fractures accumulate into more forward posture ( a hunch) these fractures are more likely to happen on the anterior side of the vertebrae => leads to kyphosis: vertebral disc compression. Vertebral disks make up 20-30% of total length of the spine: other determinants of height.

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