Skeletal Effects
The Skeletal system consists of the bones and therefore the structural strength of the body. Bones are
normally dense and comprised mainly of calcium. Throughout the lifecycle, bones are constantly reforming
in a process defined as remodeling. Bones absorb and release calcium as the body requires it. By age 30
bones begin to lose mass (Osteoporosis). Bone absorption of calcium is called Osteoblast activity and is
required for bone production. When the body requires more calcium than is being taken in from diet, the
body will catabolize calcium from the bones. Bone reabsorption or giving up calcium is called Osteoclast
activity. This process if continued will leave the bones brittle and porous. This can also result in weakened
tooth sockets and eventual tooth loss. In aging, the bones are unable to absorb the same amount of
calcium as when they were younger and a negative effect occurs depleting the bones of calcium and
reducing tissue.
As bones lose tissue, osteoporosis develops. In the spine, osteoporosis can lead to small fractures of the
vertebrae along with the shrinkage of cartilaginous discs results in a curved spine (kyphosis or lordosis)
and loss of height. Osteoporosis is also responsible for almost all hip fractures in older men and women.
Cartilage also deteriorates, which provides the cushioning between bones. With less cellular water
content, the cartilage becomes more brittle and susceptible to stress leading to arthritis.
In addition, the ligaments, which are the connective tissue between bones, become less elastic and
reduce in flexibility. Due to deterioration in cartilage and stiffening of tendons and ligaments, the motion of
joints becomes more restricted thereby decreasing flexibility. As the cushioning cartilage begins to break
down from a lifetime of use, joints become inflamed and arthritic. Stretching can help maintain joint
flexibility. Weight training can increase bone density and counter the effects of aging.
For both sexes, bone density, a measure of bone mass per unit volume, decreases at disproportionate
rates throughout the body. Bones in the vertebrae, jaw and the heads of the long bones (epiphyses)
decrease more rapidly resulting in a curved spine, tooth loss and limb fractures. During growth years,
women accumulate less bone density, particularly during puberty, than men, resulting in smaller, narrower,
and therefore more fragile bones. In aging, a reduction in sex hormones in men (testosterone) and women
(estrogen) results in bone loss.
Bone density is measured in standard deviations from the normal or young adult density. Less than 1 SD
is considered normal. Between 1 and 2.5 is considered osteopenia (bone loss). Greater than 2.5 SD is
considered Osteoporosis. Roughly 54% of postmenopausal Caucasian women are considered osteopenic
and 30% are osteoporotic.
Therefore, the consequences of bone loss as a result of age are greater in women who experience up to
three times more fractures than men. Bone mass deterioration may be slowed by calcium supplements
and weight bearing exercises.