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Physical Activity & Aging:
Implications for Health & Quality of Life in Older
Persons
Introduction
America is aging rapidly. At the beginning
of the twentieth century persons over sixty five years
of age constituted approximately four percent of the
American population, whereas they now represent more
than 12 percent of all Americans. By the year 2020 this
group is expected to increase to nearly twenty percent
of the population (U.S. Census Bureau, 1990). When expressed
in absolute number, the statistics are equally impressive,
in the United States today there are currently approximately
36 million people over the age of 65. This number is
expected to almost double to 70 million by the year
2030 (Geographic Profile, 1993). Even more remarkable
is the increase in the number of the very oldest members
of our society. The "old-old", that is, individuals
over the age of 85 years, constitute the most rapidly
growing segment of society (Shephard, 1997). By the
year 2030, it is anticipated that over eight million
Americans will be 85 years of age or older (Fowles,
1991).
There can be little doubt that such
a dramatic increase in the number of older adults will
have far reaching implications for society. Advancing
age is associated with predictable sensory, motor, and
cognitive changes, many of which have the potential
to impact on an older person's ability to function effectively
in society (Chodzko-Zajko, 1996). Fortunately, although
functional decline is an inevitable consequence of old
age, aging does not occur at a similar rate in all individuals.
In recent years, researchers have
focused considerable attention on increasing our understanding
of the factors responsible for the individual differences
in the rate and extent at which we age. It is well established
that hereditary factors play an important role in determining
the pattern of changes observed in senescence (our later
years of life). However, in addition to the genetic
factors influencing human aging, many aspects of the
aging process are also sensitive to modification through
environmental factors. Among the environmental factors
known to influence human aging are lifestyle interventions,
such as, healthy nutrition, stress reduction, smoking
cessation, and regular physical activity (Bokovy and
Blair, 1994). This review summarizes what is known about
the influence of one of these lifestyle factors: regular
physical activity.
The Benefits of Regular Physical
Activity:
In this section, a brief overview
of some of the physiological, psychological, and social
benefits of regular exercise is presented. Whenever
possible an attempt is made to address both the acute
ffects of a single bout of physical activity, as well
as the more persistent and long term effects of sustained
participation in exercise and physical activity. Because
physical activity has been defined in many different
ways, in this section, the World Health Organization's
broad and inclusive definition of physical activity
which includes all movements in everyday life, including
work, recreation, exercise, and sporting activities
(WHO, 1997) is used.
Physiological Benefits of Physical
Activity:
Participation in regular physical
activity is associated with a number of physiological
benefits (see Table 1).
Cardiovascular Function:
Maximal oxygen consumption (VO2max)
during exercise is often considered to be the single
best measure of cardiovascular fitness (McArdle, Katch
& Katch, 1994). It was initially thought that VO2max
declines at a constant rate with advancing age (about
10% per decade). However, a number of recent studies
have suggested that age-related changes in VO2max may
be more variable than initially thought (Heath et al.,
1981; Rogers et al., 1990). For example, highly trained
individuals who maintain high activity levels, often
experience little or no decline in VO2max over time
periods of a decade or more (Kasch, Wallace & VanCamp,
1985; Pollock et al., 1987). It is not possible to postpone
age-related declines in aerobic capacity forever. Nonetheless,
there is increasingly strong evidence to suggest even
modest levels of physical activity can result in significant
increases in cardiovascular efficiency in old age.
Blood Pressure:
Hypertension is a serious medical
problem which afflicts more than 20 million older Americans
(Kannel and Vokonas, 1986). On average, both systolic
and diastolic blood pressure increase significantly
with advancing age (Shephard, 1997). Several exercise
training studies have shown that physical activity can
reduce systolic and diastolic blood pressure in patients
with borderline hypertension (Goldberg & Hagberg,
1990; Kasch et al., 1988). For example, Hagberg et al.,
(1985) found that a six month program of low-intensity
walking significantly lowered both systolic and diastolic
blood pressure in hypertensive adults ranging in age
from 60-65 years. These data suggest that exercise may
have similar anti-hypertensive effects in older individuals
as those previously reported in younger populations.
Blood Lipids:
Aging is associated with increases
in both total cholesterol and serum triglycerides (Shepherd,
1997). Hypercholesterolemia and hyperlipidemia are major
medical problems which lead to the premature development
of coronary artery disease (Castelli et al., 1977).
It is now well known that exercise training is associated
with a reduction of coronary heart disease risk. Indeed
the American Heart Association (AHA) has recognized
that sedentary living is an independent risk factor
for the development of atherosclerosis (Fletcher et
al., 1992). A number of studies have shown that highly
trained masters athletes exhibit favorable biochemical
profiles (reduced low density lipoprotein cholesterol,
elevated high density lipoprotein cholesterol) when
compared with sedentary individuals of the same chronological
age (Seals et al., 1984; Tamai, et al., 1988). Because
almost all instances of favorable improvements in biochemical
profiles are associated with coincident decreases in
body weight, it is frequently difficult to dissociate
the effects of exercise from the effects of weight loss
(Shephard, 1997). These problems notwithstanding, there
appears to be sufficient evidence to suggest that regular
exercise is associated with a decrease in body fat which,
in turn, is associated with a decrease in circulating
lipids. However, the effect of exercise on blood lipids
appears to be transient and blood lipids return to pre-exercise
values within a few days of cessation of physical activity.
Table
1
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A SUMMARY
OF THE PHYSIOLOGICAL BENEFITS OF PHYSICAL
ACTIVITY FOR OLDER PERSONS
World
Health Organization, 1997
Immediate Benefits:
- Glucose levels: Physical
activity helps regulate blood glucose
levels.
- Catecholamine activity:
Both adrenalin and noradrenaline levels
are stimulated by physical activity.
- Improved sleep: Physical
activity has been shown to enhance sleep
quality and quantity in individuals
of all ages.
Long Term Effects:
- Aerobic/Cardiovascular
Endurance: Substantial improvements
in almost all aspects of cardiovascular
functioning have been observed following
appropriate physical training.
- Resistive training/muscle
strengthening: Individuals of all ages
can benefit from muscle strengthening
exercises. Resistance training can have
a significant impact on the maintenance
of independence in old age.
- Flexibility: Exercise
which stimulates movement throughout
the range of motion assists in the preservation
and restoration of flexibility.
- Balance/Coordination:
Regular activity helps prevent and/or
postpone the age associated declines
in balance and coordination that are
a major risk factor for falls.
- Velocity of movement:
Behavioral slowing is a characteristic
of advancing age. Individuals who are
regularly active can often postpone
these age-related declines.
The WHO Guidelines
have been placed in the public domain
and can be freely copied and distributed.
(WHO, 1997)
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Muscle Strength and Endurance:
Muscle strength and endurance decline
significantly with advancing age (Tzankoff & Norris,
1978; Lexell et al., 1983). Until fairly recently, strength
training was seldom emphasized as a component of exercise
programs designed for older adults. The lifting of heavy
weights requires maximal or near maximal muscular contractions
which, if incorrectly performed, can result in sharp
increases in blood pressure due to a physiological mechanism
known as the valsalva maneuver. Since these acute elevations
in blood pressure are potentially dangerous for hypertensive
individuals, in the past, most professional organizations
have chosen to de-emphasize the importance of strength
training for older adults. Recently, however, a number
of studies have examined the effect of dynamic strength
training in elderly adults. In one such study, Frontera
et al., (1988) demonstrated that older adults who trained
with weights for 12 weeks were able to gain appreciable
increases in muscular strength and endurance. No adverse
consequences associated with weight training were reported
in this study. In another widely reported study, Fiaterone
et al. (1990) demonstrated that men and women as old
as ninety years of age can safely lift very heavy weights
(80 percent of 1 repetition maximum). Remarkable gains
in strength in excess of 100 percent were reported for
some of the muscle groups trained in this study.
Since the maintenance of adequate
levels of muscular strength is critical for the successful
performance of many of the activities of daily living
(Bassey, Bendall & Pearson, 1988; Phillips &
Haskell, 1995), exercise scientists have begun to reevaluate
the importance of strength training as a component of
exercise programs for elderly adults. Both the American
College of Sports Medicine and the Surgeon General'
Report on Physical Activity and Health recommend that
muscle strengthening exercises be included as part of
the exercise training regimen for older adults (ACSM,
1995; US Surgeon General's Report, 1996).
Flexibility:
Aging is associated with changes in
the elasticity and compliance of connective tissue (Spirduso,
1995). This results in significant decreases in flexibility
and range of motion (Kuhlman, 1994; Nigg et al., 1992).
Although declines in flexibility and active range of
motion are observed in most seniors, there is some evidence
to suggest that declines in these areas are, in part
due to decreased physical activity, and that not all
older individuals lose flexibility at the same rate
(Campanelli, 1996; Morey et al., 1991). Stretching exercises
which emphasize range of motion and flexibility have
been shown to increase ankle, knee joint and lower back
flexibility in older adults (Frekany & Leslie, 1975).
The importance of pre-exercise stretching is reflected
in the fact that almost all structured exercise programs
advocate the inclusion of calisthenic exercises prior
to the commencement of aerobic exercise (Spirduso, 1995).
Balance:
Postural stability and dynamic balance
are effected by the integrity of the vestibular, visual,
and somatosensory systems, all of which undergo structural
and functional changes with advancing age (Woollacott
& Schumway-Cook, 1996). Age-related declines in
postural stability and dynamic balance are risk factors
for falls and fall-related injuries in older adult populations
(Lord et al., 1994: Tinetti, Doucette, & Claus,
1995). Although falling occurs due to a complex combination
of factors including medication use, cognitive status,
environmental hazards, sensory decline, and decreased
muscle strength and coordination, there is some evidence
to suggest that improving postural stability reduces
the likelihood of falling (MacRae, Feltner & Reisch,
1994; Tinetti et al., 1994). Improvements in balance
and body sway have been reported following participation
in a general exercise program emphasizing walking, flexibility,
and strength exercises (Lord & Castell, 1994), as
well as in response to specialized balance training
(Wolfson et al., 1996; Ian, 1998).
Psychological Benefits of
Physical Activity:
In addition to its effects on physiological variables,
physical activity can also have significant psychological
consequences. A summary of the long and short term benefits
of physical activity for psychological functioning is
included in Table 2.
General Psychological Well-being:
Although psychological health consists of both positive
and negative components, until recently, research in
the exercise sciences has tended to focus on the effects
of physical activity on negative components of psychological
health, such as, depression, anxiety, and other stress-related
disorders. McAuley and his colleagues (McAuley, 1994;
McAuley and Rudolph, 1995) have argued that it is important
to also examine the relation between physical activity
and more positive elements of psychological functioning,
including self-esteem, self-efficacy, and general well-being.
In a review of 38 studies which have examined the relation
between regular physical activity and general psychological
well-being in older adult populations, McAuley and Rudolph
(1995) found that the vast majority of studies report
a positive a ssociation between physical activity and
well-being. This relationship appears to be independent
of the mode of exercise employed (Mihalko & McAuley,
1996), however, the strength of the association is greatest
in programs of more than ten weeks in duration.
Depression and Anxiety:
It is generally accepted that the incidence of depression
increases significantly with age (LaRue, Dessonville
& Jarvik, 1985). When statistical procedures are
used to control for differences in fitness between individuals,
the association between advancing age and depression
is substantially reduced (Chodzko-Zajko, 1990). Accordingly,
data which suggest that depression increases with age
may be, at least partially, due to the tendency for
physical activity levels to decline with age and not
simply due to the passage of time. With respect
to the effect of exercise training on depression, a
number of authors have shown that participation in regular
exercise reduces depression in patients with mild to
moderate levels of clinical depression (Greist et al.,
1979, Martinsen, Medhus & Sandvik, 1985). Similarly,
studies with non-clinical populations have also reported
beneficial effects of exercise on mood state and anxiety
(Morgan & O'Connor, 1987). Despite the presence
of an association between physical activity and depression,
it has yet to be demonstrated conclusively that exercise
plays a causal role in the reduction of depression (O'Connor,
Aenchbacher, & Dishman, 1995).
Cognitive Functioning:
Age-related decrements in cognitive performance
are now well established. However, cognition is not
a unitary phenomenon and there are wide variations between
cognitive tasks with respect to the magnitude of changes
observed with advancing age. Age-related changes in
cognitive performance appear to be maximized for tasks
which require rapid and complex processing, and are
minimized for tasks which are more automatic or which
can be performed at a self-paced rate (Chodzko-Zajko
& Moore, 1994).
Despite the presence of a cross-sectional
association between fitness and cognitive performance,
no clear picture has emerged with respect to the effect
of exercise on cognitive performance. Several well controlled
studies have successfully demonstrated improvement in
cognitive performance following training (Dustman et
al., 1984; Hawkins, Kramer & Capaldi; 1992; Moul,
Goldman & Warren, 1995). However, at least as many
studies have not been able to replicate these findings
(Blumenthal et al., 1989; 1991; Panton et al., 1990).
There is some reason to believe that the magnitude of
the improvement in aerobic capacity, as well as the
demand-level of the cognitive task may be important
factors in determining the presence or absence of training
effects. However, it is important to point out that
when changes in cognitive performance have been observed
following exercise training, the magnitude of these
changes has always been small.
Table
2
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A SUMMARY
OF THE PSYCHOLOGICAL
BENEFITS OF PHYSICAL ACTIVITY FOR OLDER
PERSONS
World Health Organization,
1997 Immediate Benefits:
- Relaxation: Appropriate
physical activity enhances relaxation.
- Reduces Stress and
Anxiety: There is evidence that regular
physical activity can reduce stress
and anxiety.
- Enhanced Mood State:
Numerous people report elevations in
mood state following appropriate physical
activity.
Long Term effects:
- General Well Being:
Improvements in almost all aspects of
psychological functioning have been
observed following periods of extended
physical activity.
- Improved Mental Health:
Regular exercise can make an important
contribution in the treatment of several
mental illnesses, including depression
and anxiety neuroses.
- Cognitive Improvements:
Regular physical activity may help postpone
age related declines in Central
Nervous System processing speed and
improve reaction time.
- Motor Control and
Performance: Regular activity helps
prevent and/or postpone the age associated
declines in both fine and gross motor
performance.
- Skill Acquisition:
New skills can be learned and existing
skills refined by all individuals regardless
of age.
The WHO Guidelines
have been placed in the public domain
and can be freely copied and distributed,
(WHO, 1997)
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Social Implications of Regular
Physical Activity:
The vast majority of research studies
examining the effects of exercise on the aging process
have focused on the physiological and psychological
benefits of activity. However, it would be inappropriate
to conclude this section without a brief comment about
the importance of physical activity for the social functioning
of older people. In recent World Health Organization
Guidelines for
Promoting Physical Activity in Older Persons (WHO, 1997)
a number of significant short and long-term effects
of physical activity on socio-cultural variables are
discussed (see Table 3)
Who should be Physically Active?
Until fairly recently physical activity
programming for older adults has tended to focus on
a relatively small and healthy subgroup of the older
adult population (Chodzko-Zajko, 1995). However, it
is now clear that beneficial effects of regular physical
activity can be observed in almost all older persons
regardless of their physical health. Several excellent
and well publicized studies have focused our attention
on the benefits of regular physical activity in those
cohorts of seniors who were previously thought to be
"too old" or "too frail" to partake
in structured exercise programming (Fiatarone &
Evans, 1990).
Physical Activity Programs
for Older Adults:
It is not possible to formulate generic
exercise prescriptions which can be applied across the
board for all older adults. Individual differences in
health status, physical fitness and previous exercise
experience require that exercise prescription be tailored
to meet the specific needs of each person. Older adults
should be encouraged to seek advice from a health or
exercise professional, who can assist them in the preparation
of an optimal program designed to meet their individual
needs. It is recommended that previously sedentary individuals
over the age of 40 years should obtain a thorough medical
examination before embarking on an exercise program
(ACSM 1995). In cases where a physician's examination
is not possible, pre-exercise screening questionnaires
have been developed which can assist in identifying
contraindications to exercise (Cardinal and Cardinal,
1995).
In the past, a large percentage of
the elderly population has remained sedentary due to
the mistaken belief that they were not candidates for
participation in regular physical activity. While there
is an extremely small number of individuals for whom
exercise is medically contraindicated, the vast majority
of the elderly populations can benefit from participation
in some form of physical activity (WHO, 1997). The major
absolute contraindications to exercise training are
recent ECG changes or myocardial infarction, unstable
angina, uncontrolled arrhythmias, third degree heart
block, and congestive heart failure (ACSM, 1995). The
emergence of specialized programs for specific clinical
populations, such as, cardiac rehabilitation programs,
the Arthritis Foundation's PACE program and programs
for diabetics, are a testament to the realization that
the benefits of physical activity apply across the continuum
of health levels and exercise need not be restricted
to "jocks" and exercise fanatics.
The WHO Guidelines for Promoting Physical
Activity acknowledge the wide diversity of different
exercise regimens which can be followed by older adults.
Exercise can be an individual or group activity, it
can be carried out in supervised or unsupervised settings.
It is not necessary to have expensive facilities and
equipment, and that successful programs are quite possible
with very limited resources (WHO, 1997). While recognizing
the importance of individualized exercise prescription,
it is nonetheless possible to make some comments about
general principles of exercise prescription which may
be of value when designing exercise programs for older
adults.
Table
3
|
A SUMMARY
OF THE SOCIAL
BENEFITS OF PHYSICAL ACTIIVTY FOR OLDER
PERSONS
World
Health Organization, 1997
Immediate Benefits:
- Empowering Older
Individuals: A large proportion of the
older adult population voluntarily adopts
a sedentary lifestyle which eventually
threatens to reduce independence
and self-sufficiency. Participation
in appropriate physical activity can
help empower older individuals and assist
them in playing a more active role in
society.
- Enhanced Social and
Cultural Integration: Physical activity
programs, particularly when carried
out in small groups and/or in social
environments enhance social and
inter-cultural interactions for many
older adults.
Long Term Effects:
- Enhanced Integration:
Regularly active individuals are less
likely to withdraw from society and
more likely to actively contribute to
the social milieu.
- Formation of new
friendships: Participation in physical
activity, particularly in small groups
and other social environments, stimulates
new friendships and acquaintances.
- Widened Social and
Cultural Networks: Physical activity
frequently provides individuals with
an opportunity to widen available social
networks.
- Role maintenance
and new role acquisition: A physically
active lifestyle helps foster the stimulating
environment necessary for maintaining
an active role in society, as well as
for acquiring positive new roles.
- Enhanced Intergenerational
Activity: In many societies, physical
activity is a shared activity which
provides opportunities for intergenerational
contact thereby diminishing stereotypic
perceptions about aging and the elderly.
The WHO Guidelines
have been placed in the public domain
and can be freely copied and distributed.
(WHO, 1997)
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Activity Mode:
Low and moderate intensity, rhythmic
activities which utilize large muscle groups are optimal
for the enhancement of aerobic capacity. Common examples
of such activities are walking, jogging, bicycling,
and swimming. The particular activity selected by an
individual is often a matter of personal preference.
However, among many older persons, orthopedic and/or
other medical factors may restrict the number of available
options. In addition to these exercises, an increasing
number of older adults participate in other activities,
such as, various forms of dancing and weight training.
While these activities may not be appropriate for all
older individuals, there is little doubt that many people
can obtain significant physiological benefits and much
enjoyment from these forms of activity (ACSM, 1995).
Training Frequency:
In order to obtain a reliable training
effect, it is generally recognized that a frequency
of training two to three times per week is required.
However, habitual exercisers often exercise five or
six days per week without adverse consequences (ACSM,
1995). It is important to note that many of the physiological,
psychological and social benefits of physical activity
require regular and continuous participation and can
be rapidly reversed by a return to inactivity.
Duration of Exercise:
Most structured exercise programs
are designed to last about 45 minutes - 1 hour. This
time period is typically divided up into 15-20 minutes
of warm up and stretching, 20-30 minutes of aerobic
activity and 5-10 minutes of cool down. While this format
is flexible, there is some evidence to suggest that
the aerobic component of exercise programs should last
at least 20 minutes in order to obtain optimal cardiovascular
benefits (Spirduso, 1995). For many sedentary and frail
individuals, continuous activity for 45-60 minutes may
be an unrealistic goal, at least at the onset of an
exercise program. For these individuals more modest
exercise targets should be set. As these individuals
slowly become accustomed to renewed physical activity,
exercise prescriptions can be adjusted accordingly.
Intensity of Exercise:
It is a popular misconception that
high intensity exercise is required for significant
physiological gain. The saying "no pain, no gain"
is simply not true. Such misconceptions perpetuate inappropriate
attitudes about exercise and result in large numbers
of individuals avoiding potentially beneficial and enjoyable
behaviors. Many older adults first learned to exercise
at a time when high intensity exercise was widely considered
to be more effective than more modest levels of activity.
In recent years there has been extensive debate regarding
the utility of traditional exercise prescriptions when
applied to the sedentary population (Blair, 1994). Rather
than adopt an absolutist stance regarding the minimum
frequency, duration, and intensity of exercise necessary
to achieve a training effect, it may be more prudent
to encourage individuals to simply increase or maintain
their activity levels without setting rigid (and frequently
intimidating) exercise prescriptions.
Conclusions And Recommendations:
The scientific and medical evidence
reviewed above clearly demonstrates that participation
in regular physical activity is associated with tangible
health benefits for almost all older adults.
The disappointingly low rates of participation
in physical activity among older persons has led to
considerable speculation with respect to why so many
seniors choose not to be active. Commonly cited reasons
for the failure to engage in regular physical activity
include lack of time, money, or motivation (Lee, 1993).
Additionally, the lack of safe, accessible facilities
that are nearby and convenient to attend are often mentioned
as perceived barriers to physical activity (Lee, 1993).
There are also other reasons that pertain more specifically
to older adults. These include societal stereotypes
about aging and activity and the lack of social support
for physical activity (Duncan & McAuley, 1993).
A number of researchers have suggested that society
holds certain attitudes about what is or is not appropriate
behavior for particular age groups (Lee, 1993; Ostrow,
Jones, & Spiker, 1981). For example, the disengagement
theory of aging suggests that society encourages older
adults to slow down and take it easy and, thus, acts
to discourage participation in physical activity (McPherson,
1990). Others have suggested that older women, in particular,
often lack meaningful role models who are physically
active (O'Brien & Vertinsky, 1991).
Although it is beyond the scope of
this paper to propose specific strategies for increasing
the physical activity levels of the older adult population,
there can be little doubt that considerable additional
efforts are needed. Within the area of education, there
is a need to increase awareness of the role of physical
activity in healthy aging throughout all segments of
society. In most countries, physicians are presently
inadequately prepared to advise their older patients
in the area of exercise and physical activity. Medical
school curricula pay insufficient attention to the importance
of preventive medicine in general, and almost no attention
to specific issues such as exercise prescription and
evaluation. Similarly, few allied health professions
have developed comprehensive curricula focusing on the
special activity needs of older persons. For example,
within exercise science and physical education, almost
all universities offer specialist degrees and concentrations
in childhood physical education, in contrast, very few
offer courses in physical activity and aging (Jones
& Rikli, 1994).
In addition to educating health professionals,
it is also important to disseminate information to health
policy makers in both the public and private sectors.
Elected representatives at all levels of government
should be informed about the many benefits associated
with promoting physical activity. Leaders of the health
insurance industry must be educated about the cost effectiveness
of preventative exercise interventions (Shephard, 1997).
Unless we are able to successfully disseminate information
to this segment of our society, it is doubtful that
we will be able to develop a truly cooperative and comprehensive
strategy forsuccessful aging.
Finally, but most importantly, we
must not forget that the most important people in the
education process are the older people themselves. A
large number of senior citizens remain unaware of the
health benefits of physical activity. Many older adults
continue to believe that physical activity is only for
the physically fit and elite seniors. On the contrary,
there is now strong evidence that virtually all older
adults, even the sedentary and physically frail are
candidates for some form of physical activity. Extensive
efforts are needed to spread the word about physical
activity and successful aging to the population at large.
Parts of this review have been
adapted with permission from:
Chodzko-Zajko, W.J. (1998). The Physiology of Aging
and Exercise, in R.T. Cotton & C.Ekeroth (Eds).
Exercise for Older Adults, Champaign, IL., Human Kinetics
Published quarterly
by the
President's
Council on
Physical Fitness and Sports
Washington, D.C.
|
Wojtek
J. Chodzko-Zajko, Ph.D.
School of Exercise, Leisure and
Sport Kent State University
Kent, OH 44242-0001
|
Co-edited
by
Drs. Chuck Corbin and Bob
Pangrazi Arizona State University
|
The PCPFS
Research Digest
is available on line at
http://www.indiana.edu/~preschal
|
|
Physical Activity
and Fitness Quote
"Physiological
responses of elderly adults to exercise training
are essentially similar to those experienced by younger
individuals. Some of the more common physiological
adaptations
are improved cardiovascular function, an increase in
muscular
strength and endurance, and lowered blood pressure."
Wojtek J. Chodzko-Zajko,
Ph.D.
School of Exercise, Leisure, and Sport
Kent State University Kent, OH 44242-0001
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