Exercise Counseling
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Recommendation
Clinicians should counsel all patients to engage in a
program of regular physical activity, tailored to their
health status and personal lifestyle.
Burden of Suffering
Physical inactivity has been associated with a number of
debilitating medical conditions in the United States,
including coronary artery disease (CAD), hypertension,
noninsulin-dependent diabetes mellitus (NIDDM), and
osteoporosis. CAD is the leading cause of death in the
United States, accounting for about 1.5 million myocardial
infarctions and over 520,000 deaths each year.1,2 About
400,000 Americans are victims of sudden death each year,
due primarily to underlying atherosclerotic disease.
Hypertension, which occurs in up to 58 million Americans,3
is a leading risk factor for CAD, as well as for other
serious diseases such as renal disease, retinopathy, and
stroke. Cerebrovascular disease alone accounts for about
150,000 deaths each year and is the third leading cause of
death in the United States.1 NIDDM is an important risk
factor for CAD, cerebrovascular disease, retinopathy, and
hypertension. Nearly 6 million Americans suffer from
NIDDM.4 Osteoporosis is responsible for an estimated 1.3
million fractures each year.5 About one-quarter of all
women over age 60 have spinal compression fractures, and
about 15% of women sustain hip fractures during their
lifetime.6,7 There is a 15-20% reduction in expected
survival in the first year following a hip fracture.8 Hip
fractures cost the United States over $7 billion each year
in direct and indirect costs.9
Efficacy of Risk Reduction
Studies have shown that men who are physically active on a
regular basis have a lower overall mortality than those who
are physically inactive.10,11 Exercise appears to be
especially effective in improving health status in six
disease-specific areas: CAD, hypertension, obesity, NIDDM,
osteoporosis, and diminished psychological well-being.
Physically inactive persons are twice as likely to develop
CAD as are persons who engage in regular physical
activity.12 Evidence from cohort studies has shown a
consistent association between physical activity and
reduced incidence of CAD.11,13,14 Similar benefits from
exercise have been reported in older men (up to age
75);15,16 efficacy in women is presumed on the basis of
extrapolation. Studies have also shown that exercise may
have a beneficial effect on plasma lipoprotein
concentrations.17 A possible criticism of the apparent
benefits of exercise is that those who are physically
active are at decreased risk for CAD by virtue of
self-selection--that is, persons who choose to exercise may
be inherently more healthy and have fewer overall risk
factors for CAD. However, studies controlling for such
confounding variables have found that the effects of
exercise are independent of other CAD risk factors, and
that the cardiovascular benefits may even be augmented in
the presence of other risk factors for CAD.16,18 It has
also been shown that the type of individual who adopts
athletic behavior is not protected from CAD if regular
exercise is discontinued. A study of former college
athletes who had become physically inactive found that CAD
risk in this cohort was similar to that of inactive alumni
who had not been college athletes.19
Regular exercise is an important means of improving caloric
balance and preventing obesity. A large body of
epidemiologic evidence supports an association between
physical activity and weight control, even after
controlling for dietary factors.20 The contribution of
physical activity to daily caloric expenditure is often
relatively small. For example, a daily one-mile walk may
amount to only a 4% contribution to total daily
expenditure. However, weight gain often occurs as a result
of small differences between caloric intake and
expenditures, and therefore it is possible through regular
exercise to achieve a caloric balance that prevents
progressive increases in weight. Although exercise may
increase caloric intake, it is accompanied by an even
greater increase in caloric expenditure, so that a negative
caloric balance is maintained.21
Exercise may reduce the risk of developing hypertension and
NIDDM. Cohort studies suggest that physically inactive
persons have a 35-52% greater risk of developing
hypertension than those who exercise; this effect appears
to be independent of other risk factors for
hypertension.22,23 The average reduction in blood pressure
achieved through regular exercise has been estimated to be
about 10 mm Hg.24 Physical activity is also associated
with increased insulin sensitivity and glucose clearance,
and epidemiologic studies of South Pacific natives suggest
that differences in physical activity may have contributed
to the increased prevalence of NIDDM in this
population.25,26 Further evidence is needed, however, to
prove that exercise improves glucose tolerance or that it
reduces the risk of developing NIDDM.27
Weight-bearing physical activity may also reduce bone loss
in postmenopausal women.28-34 Further research is needed
to prove that bone mineral content is improved sufficiently
to reduce the incidence of osteoporosis-related fractures.
Although studies suggest the risk of hip fractures is lower
in persons who exercise regularly,35,36 prospective
evidence is necessary to prove that this effect is due
specifically to exercise. Additional studies are also
needed to determine whether the risk of fall-related
fractures during exercise offsets the intended benefits of
preventing osteoporosis.
A commonly mentioned benefit of regular exercise is
improved affect (positive mood, reduced depression, lowered
anxiety).37,38 The nature of the relationship between
exercise and mental health is poorly understood. It is
known that physically active persons report higher levels
of self-esteem, perhaps in response to improved personal
appearance and self-image. No well-designed studies have
shown that the incidence of clinically confirmed
psychiatric disorders can be reduced through exercise.39
Most studies have used different definitions for physical
activity,40 and therefore it is not clear from the evidence
exactly what form of exercise is most beneficial. To
improve cardiovascular fitness, it is known that exercise
cannot be performed occasionally or seasonally,41 nor can
one expect protection from CAD by having exercised
regularly in the past.19 The cardiovascular effects at
increasing levels of exercise intensity appear to operate
in a dose-response relationship, with modest benefits at
low energy expenditures (150-500 kcal/week) and maximal
benefits at higher levels (2000-3500 kcal/week).10,19
Small increases in activity among the most inactive persons
appear to be associated with the largest magnitudes of risk
reduction. It has traditionally been thought that an
improvement in cardiovascular fitness requires a threshold
level of aerobic intensity during an exercise session and a
minimum frequency of sessions, and this has served as the
basis for a number of similar exercise criteria. Three of
these include: (1) dynamic movement of large muscle groups
for at least 20 minutes, three or more days per week,
performed at an intensity of at least 60% of
cardiorespiratory capacity; (2) intensity of 50-100% of
cardiorespiratory capacity, frequency of two to four times
per week, duration of 15-45 minutes, program length of 5-11
weeks; and (3) achieving and maintaining a pulse rate equal
to the formula: (220 - age) x 70%.42,43
It has also become clear that many of the health benefits
of exercise may be obtained even at lower intensity and
frequency levels. Furthermore, vigorous exercise may not
be advisable in some individuals, especially those who are
at increased risk of injury or cardiovascular complications
from vigorous physical activity (e.g., the elderly). A
number of studies suggest that the threshold intensity for
improving cardiovascular fitness may be lower than
previously thought and that activities such as brisk
walking, climbing stairs, and gardening can be
beneficial.11,18,40,41,44 These benefits have been
validated in studies of low intensity activity in elderly
persons44-47 and those with poor baseline fitness.43
Inactive persons, as well as those who are hypertensive or
obese, can benefit significantly from even modest increases
in physical activity. In addition, as described above,
persons who engage in low intensity exercise may also enjoy
the benefits of exercise other than those relating to CAD;
these include improved strength and flexibility (which may
reduce the risk of falls in the elderly; see Chapter 52),
increased bone density, and improved mood.
The benefits of exercise must be weighed against its
potential adverse effects, which include injury,
osteoarthritis, and, rarely, sudden death. Although
injuries are commonly reported in competitive sports, there
are few reliable data on the incidence of injuries during
typical noncontact exercises.48,49 It is currently thought
that most injuries during exercise are preventable. They
often occur as a result of excessive levels of physical
activity, dramatic incremental changes in activity level
(especially in persons with poor baseline fitness), and
improper exercise techniques or equipment. A second
concern is that long-term physical activity may accelerate
the development of osteoarthritis in major weight-bearing
joints (e.g., hips, knees). Cross-sectional studies in
long-distance runners, however, have been unable to
demonstrate a strong association between exercise and
osteoarthritis.50-52 A third concern is the risk of sudden
death, which is known to be increased during vigorous
physical activity.53 Studies suggest that sedentary
persons who engage in vigorous activity are at greater risk
for sudden death than are those who are regularly active.54
In fact, due to the cardiovascular benefits of exercise,
the overall risk of sudden death (both during and not
during exercise) in men who engage regularly in high levels
of physical activity is considerably lower than in
sedentary men.54
Effectiveness of Counseling
At least 40% of the U.S. population is considered
sedentary, and as many as 80-94% fail to exercise at an
adequate level to obtain cardiorespiratory benefit.55,56
Thus, the majority of patients seen by physicians could
potentially benefit from encouragement to increase physical
activity levels. There is, however, a limited amount of
information regarding the ability of physicians to
influence the exercise behavior of patients. Studies that
have demonstrated benefits from counseling provide little
information about long-term compliance and are of limited
generalizability, because the form of counseling, type of
patients, or clinical setting have not been representative
of typical primary care physician counseling of healthy
patients.57-63 It is known from surveys, however, that
negative perceptions of exercise activity (e.g.,
inconvenience, cost of equipment, discomfort) can often act
as powerful disincentives.64,65 In particular,
high-intensity activities and greater perceived exertion
are major barriers to adherence to physical activity
programs, especially in sedentary persons over the age of
35. Persons most likely to adopt vigorous exercise
programs are those already exercising at a moderate
level.65
Recommendations of Others
Although counseling patients to exercise is widely
recognized as clinically prudent, there are few official
recommendations for physicians to include exercise
counseling in the periodic health examination. The
American College of Sports Medicine has issued specific
guidelines on the medical contraindications to exercise.66
Discussion
Despite the absence of direct evidence that physician
counseling can increase the physical activity of
asymptomatic patients, the intervention is warranted
because of the numerous potential health benefits
associated with physical activity. Physical inactivity
results in a slightly lower relative risk for CAD than the
commonly accepted risk factors of hypertension,
hypercholesterolemia, and cigarette smoking, but it is a
much more common cardiac risk factor in the U.S.
population.67 Physical inactivity is also a risk factor
for other serious diseases, such as hypertension and
obesity. Thus, from a population perspective, even modest
increases in physical activity levels could have large
public health implications.67
Nonetheless, it is important for clinicians to use
discretion in recommending appropriate forms of physical
activity for patients. In addition to considering
potential contraindications in persons with underlying
medical disorders, it is also necessary to design an
exercise program with an awareness of potential barriers to
compliance in the patient's personal lifestyle. Since some
patients will be unable or unwilling to engage in any high
intensity activities, recommending low intensity exercise
for certain individuals may ultimately achieve greater
health benefits than urging vigorous exercise activities.
Brisk walking, for example, offers improved cardiovascular
fitness along with the compliance-enhancing features of
convenience, lower perceived discomfort, and safety. The
addition of a strong arm swing (aerobic or "pace" walking),
although slightly more difficult technically, is a simple
measure to increase the aerobic activity of walking.
Clinical Intervention
Clinicians should provide all patients with information on
the role of physical activity in disease prevention and
assist in selecting an appropriate type of exercise.
Factors that should be considered in designing a program
include medical limitations and activity characteristics
that both improve health (e.g., weight-bearing, increased
caloric expenditure, enhanced cardiovascular fitness, low
potential adverse effects) and enhance compliance (e.g.,
low perceived exertion, cost, inconvenience). The patient
should also be given instructions on how to perform the
exercise safely to reduce the risk of injuries. The
patient should be encouraged to set at least one specific
exercise goal; the initial target should be only a small
increment above baseline status. Beginners should
emphasize regular, rather than vigorous, exercise; an
appropriate short-term goal is to engage in regular walking
at least three times per week for at least 30 minutes.
Ultimately, over a period of several months, the patient
should progress to a level that achieves increased
cardiovascular fitness (e.g., 30 minutes of daily brisk
walking). For most healthy persons, maximum cardiovascular
fitness can be achieved by a program of vigorous aerobic
exercise for 15-45 minutes, two to four times per week,
during which a pulse rate of about (220 - age) x 70% is
reached and maintained. Clinicians who are unable to
design an effective exercise program may wish to refer
patients to an accredited fitness center or exercise
specialist.
Note: See Appendix A for the U.S. Preventive Services Task
Force Table of Ratings for this topic. See also the
relevant Task Force background paper: Harris SS, Caspersen
CJ, DeFriese GH, et al. Physical activity counseling for
healthy adults as a primary preventive intervention in the
clinical setting; report for the U.S. Preventive Services
Task Force. JAMA 1989;261:3590-8.
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