Osteoporosis and aging; Muscle weakness associated with aging
Changes in posture and gait (walking pattern) are as universally associated with aging as changes in the skin and hair.
The skeleton provides support and structure to the body. Joints are the areas where bones come together. They allow the skeleton to be flexible for movement. In a joint, bones do not directly contact each other. Instead, they are cushioned by cartilage in the joint, synovial membranes around the joint, and fluid.
Muscles provide the force and strength to move the body. Coordination is directed by the brain but is affected by changes in the muscles and joints. Changes in the muscles, joints, and bones affect the posture and gait, and lead to weakness and slowed movement.
Bone mass or density is lost as people age, especially in women after menopause. The bones lose calcium and other minerals.
The spine is made up of bones called vertebrae. Between each bone is a gel-like cushion (intervertebral disk). The trunk becomes shorter as the disks gradually lose fluid and become thinner.
In addition, vertebrae lose some of their mineral content, making each bone thinner. The spinal column becomes curved and compressed (packed together). Bone spurs, caused by aging and overall use of the spine, may also form on the vertebrae.
The foot arches become less pronounced, contributing to a slight loss of height.
The long bones of the arms and legs, although more brittle because of mineral loss, do not change length. This makes the arms and legs look longer when compared with the shortened trunk.
The joints become stiffer and less flexible. Fluid in the joints may decrease, and the cartilage may begin to rub together and erode. Minerals may deposit in and around some joints (calcification). This is common in the shoulder.
Hip and knee joints may begin to lose joint cartilage (degenerative changes). The finger joints lose cartilage and the bones thicken slightly. Finger joint changes are more common in women and may be hereditary.
Some joints, such as the ankle, typically change very little with aging.
Lean body mass decreases, caused in part by loss of muscle tissue (atrophy). The rate and extent of muscle changes seem to be genetically determined. Muscle changes often begin in the 20s in men and the 40s in women.
Lipofuscin (an age-related pigment) and fat are deposited in muscle tissue. The muscle fibers shrink. Muscle tissue is replaced more slowly, and lost muscle tissue may be replaced with a tough fibrous tissue. This is most noticeable in the hands, which may appear thin and bony.
Changes in the muscle tissue, combined with normal aging changes in the nervous system, cause muscles to have less tone and ability to contract. Muscles may become rigid with age and may lose tone, even with regular exercise.
EFFECT OF CHANGES
Bones become more brittle and may break more easily. Overall height decreases, mainly because of shortening of the trunk and spine.
Inflammation, pain, stiffness, and deformity may result from breakdown of the joint structures. Almost all elderly people are affected by joint changes, ranging from minor stiffness to severe arthritis.
The posture may become more stooped (bent) and the knees and hips more flexed. The neck may become tilted, and the shoulders may narrow while the pelvis becomes wider.
Movement slows and may become limited. The walking pattern (gait) becomes slower and shorter. Walking may become unsteady, and there is less arm swinging. Older people become tired more easily, and have less energy.
Strength and endurance change. Loss of muscle mass reduces strength. However, endurance may be enhanced somewhat by changes in the muscle fibers. Aging athletes with healthy hearts and lungs may find that performance improves in events that require endurance, and decreases in events that require short bursts of high-speed performance.
Muscle weakness contributes to fatigue, weakness, and reduced activity tolerance. Joint problems are extremely common. This may be anything from mild stiffness to debilitating arthritis (see osteoarthritis).
Some elderly people have reduced reflexes. This is most often caused by changes in the muscles and tendons, rather than changes in the nerves. Decreased knee jerk or ankle jerk can occur. Some changes, such as a positive Babinski's reflex, are not a normal part of aging.
Involuntary movements (muscle tremors and fine movements called fasciculations) are more common in the elderly. Inactive or immobile elderly people may experience weakness or abnormal sensations (paresthesias).
Muscle contractures may occur in people who are unable to move on their own or have their muscles stretched through exercise.
Exercise is one of the best ways to slow or prevent problems with the muscles, joints, and bones. A moderate exercise program can help you maintain strength and flexibility. Exercise helps the bones stay strong.
Consult with your health care provider before beginning a new exercise program.
A well-balanced diet with adequate amounts of calcium is important. Women need to be especially careful to get enough calcium and vitamin D as they age. Postmenopausal women, and men over age 65, need 1,200 - 1,500 mg of calcium and 400 - 800 international units of vitamin D per day. If you have osteoporosis, talk to your doctor about prescription treatments.
Minaker KL. Common clinical sequelae of aging. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 23.