computer, and playing video games replacing
physical activities. Numerous clinical research
studies correlate such physical inactivity with the
rise in childhood OBESITY AND HEALTH conditions
such as type 2 DIABETES, HYPERLIPIDEMIA, and
OSTEOARTHRITISthat typically do not appear until
middle age or later.
Health experts recommend an hour a day of
moderate physical activity for children and adoles-
cents, though estimate 60 percent or more do not
meet that recommendation. The health risks asso-
ciated with physical inactivity not only carry into
adulthood but appear to be more severe. Aerobic
capacity—the body’s ability to use oxygen effi-
ciently—reaches its peak in the early 20s and then
begins a gradual decline. Muscle mass andBONE
DENSITY are also at their peak in the early 20s.
Daily physical activity in late ADOLESCENCEappears
capable of extending aerobic capacity and muscu-
loskeletal strength well into adulthood.
Older Adults and ExerciseA physically active adult has an aerobic capacity,
measured as VO2max, up to 25 percent greater than
a person of comparable age who does not exercise.
Such a difference becomes increasingly significant
with advancing age. Between age 20 and age 40
aerobic capacity declines 8 to 12 percent. Between
age 40 and age 70 aerobic capacity declines about
10 percent per decade. After age 70 aerobic capac-
ity declines 20 percent per decade. When daily
physical activity is an element of lifestyle through-
out life, the decline in aerobic capacity signifi-
cantly slows. A 70-year-old who has a moderate
to good FITNESS LEVEL(exercises at or beyond the
minimum PHYSICAL ACTIVITY RECOMMENDATIONS) has
an aerobic capacity comparable to that of a person
10 to 20 years younger.
Such a difference correlates to lower HEART RATE,
lowerBLOOD PRESSURE, stronger muscles and bones,
increased HORMONE sensitivity and endocrine
response, smoother and more regular gastrointesti-
nal function, and even greater elasticity to the SKIN.
These factors lower the risk for numerous health
conditions including HEARTdisease, HEART ATTACK,
STROKE, OSTEOPOROSIS, hip FRACTURE, type 2 diabetes,
OBESITY, SEXUAL DYSFUNCTION, and various forms of
cancer. Though no clinical evidence as yet supports
exercise as a panacea for aging, researchers have
gone so far as to say that lifestyle factors such as
daily exercise, nutritious EATING HABITS, and not
smoking have the capability to eliminate 85 percent
or more of acquired CARDIOVASCULAR DISEASE(CVD).
As well, numerous studies affirm the beneficial
effects of exercise toward preventing injury and
supporting overall health.
Daily physical activity becomes more significant
with advancing age also because the body natu-
rally begins to change in ways that diminish LEAN
MUSCLE MASS, muscle strength, JOINTflexibility, gas-
trointestinal function, and hormone sensitivity.
Around age 50 hormonal shifts in both men and
women result in loss of muscle tissue, with fat
often replacing this loss, and bone density. After
age 70 muscle strength, bone density, and aerobic
capacity decline in men and women alike. In men
these changes are less pronounced; in women par-
ticularly they can have catastrophic health conse-
quences if not detected and treated. A woman’s
risks for heart disease and osteoporosis jump after
MENOPAUSE, largely the consequence of the drop in
ESTROGENS. The risk of hip fracture due to lost bone
density rises in men and women alike after age- Though daily exercise cannot prevent such
changes from occurring, it can mitigate their
severity and help maintain good QUALITY OF LIFE.
Older people who have chronic or serious
health conditions may have limited ability to par-
ticipate in physical activities. Conditions such as
HEART FAILUREand CHRONIC OBSTRUCTIVE PULMONARY
DISEASE (COPD) may limit aerobic capacity, for
example. Osteoarthritis and RHEUMATOID ARTHRITIS
may restrict movement. Despite the limitations
chronic health conditions may impose on physical
activity, they also benefit from regular exercise
however modest. A health professional such as a
physical therapist, an exercise physiologist, or a
physiatrist (physician who specializes in rehabili-
tation medicine) can help develop an appropriate
physical activity regimen for a person who has a
chronic or debilitating health condition.
See also ANABOLIC STEROIDS AND STEROID PRECUR-
SORS; DISABILITY AND EXERCISE; WEIGHT LOSS AND
WEIGHT MANAGEMENT; YOGA.
blister prevention Methods to reduce irritation
to SKIN surfaces from friction. The feet are the
most common site of blisters acquired duringblister prevention 215̇