Exercising & Weight Training At Any Age
Adding strength training to a program of regular physical activity
will help to decrease the risk of chronic diseases while improving
quality of life and functionality, allowing people of all ages to
improve and maintain their health and in dependent lifestyle.
Increasing physical activity and participation in an aerobic
endurance exercise program have been shown to decrease the risk
of chronic diseases (e.g., coronary heart disease [CHD], stroke,
osteoporosis, diabetes, obesity/weight control), which have become
the leading causes of morbidity and mortality in the United States.
The American Heart Association (AHA) has identified physical inactivity
as a primary risk factor for the development of CHD along with cigarette
smoking, high blood pressure, and elevated levels of cholesterol.
As an intervention, the American College of Sports Medicine (ACSM),
the AHA, and the Surgeon Generals Report on Physical Activity and
Health all have established guidelines for aerobic exercise programs
designed to positively affect health status. These recommendations
are based on a preponderance of evidence establishing the effect
of exercise on disease prevention (see Figure 14.1).
The effects of resistive type exercise (strength training) on health
status have been largely overlooked. Traditionally, strength training
has been seen as a means of improving muscular strength and endurance
(muscle mass) and power, but not as a means for improving health.
There is increasing evidence that strength training plays a significant
role in many health factors (see Figure 14.1). The ACSM (1990, 1995),
AHA (1995), and the Surgeon Generals Report on Physical Activity
and Health (1996) all have recognized the importance of strength
training as an important component of health. These organizations
have recommended performing 1 set of 812 repetitions of 810 exercises
23 times per week for persons under 50 years of age and the same
regimen using 1015 repetitions for persons over 50 years of age.
The research and rationale for this exercise prescription have been
reviewed (ACSM, 1990; Pollock et al., 1994; Feigenbaum & Pollock,
1997). Although greater intensity (fewer repetitions and greater
weight) with multiple sets can elicit greater improvements in strength
and power, it may not be appropriate for older nonathletic participants.
A regimen of 812 or 1015 repetitions appears to be an adequate balance
for developing both muscular strength and endurance. The research
suggests that 8090% of the strength gains can be elicited using
this regimen compared to the high volume types of programs. Thus,
because time is an important factor for program compliance, the
above recommended guidelines seem appropriate. Although more research
is necessary to confirm the best combination of intensity (repetitions,
weight, sets) for older or more fragile participants, it appears
that the 1015 repetition guideline may create less joint stress
and injury than the 812 repetition program.
Improving muscular strength has been traditionally viewed as important
for athletes, competitive weightlifters, and bodybuilders, but not
for improving health status. Recent evidence indicates that this
conception is no longer true. In this paper we will provide information
concerning how strength training can influence health and disease
IMPROVEMENTS IN STRENGTH AND FUNCTION
Aging has been associated with a decrease in muscle mass and
strength (Larsson et al., 1979).
This decrease in strength is linked to decreased mobility, decreased
functionality, and increased risk of falling in older people (Bendall
et al., 1989; Fiatarone & Evans, 1990). Falls have been identified
as the most frequent cause of injury-related mortality in the elderly
(Fife et al., 1984). According to Greenspan et al. (1994), 90% of
all hip fractures in the elderly occur as a result of a fall. The
authors also suggested that to help prevent the risk of falling,
interventions should include exercise designed to improve quadriceps
strength, neuromuscular function, and gait. Nevitt et al. (1991)
conducted a prospective study to determine the risk factors that
lead to injurious falls in the elderly. They reported that the fallers
ability to protect him- or herself during the fall affected the
risk of injury. Upper and lower extremity strength, reaction time,
and time to complete a cognitive test were associated with risk
of falling and injury. The authors recommended that interventions
intended to reduce the risk of falling and injury should include
strength training and exercise. Fiatarone et al. (1994) examined
the effect of 10 weeks of resistance exercise for the legs only
on muscle strength and function in elderly adults (mean age, 87
0.6 yr). Resistance exercise increased muscle strength (113%), gait
velocity (12%), stair climbing power (28%). Fiatarone et al. (1990)
reported that eight weeks of resistance exercise for the legs improved
strength and function in nonagenarians (mean age 901 yr). Quadriceps
strength improved 174% and tandem gait speed increased 48% following
The Surgeon Generals Report on Physical Activity and Health stated
that developing muscular strength can improve ones ability to perform
tasks and reduce the risk of injury.
The report goes on to say that resistance training may contribute
to better balance, coordination, and agility that may help prevent
falls in the elderly.
LOW BACK PAIN AND STRENGTH
Low back pain and spinal disorders are the predominant reason
for disability in the workforce. It is estimated that chronic low
back pain accounts for nearly 80% of the annual cost of low back
disorders even though this classification represents only 10% of
all spinal disorders (Spengler et al., 1986). Lack of lumbar strength
has been associated with the development of low back pain and dysfunction.
Russell et al. (1990) reported increased lumbar strength and decreased
low back pain following eight weeks of isolated lumbar extension
exercise in subjects with chronic low back pain. Risch et al. (1993)
examined the effect of 10 weeks of lumbar extension exercise on
patients with chronic low back and reported decreased low back pain,
physical and psychosocial dysfunction. The results also showed a
significant improvement in lumbar extension strength. Nelson et
al. (1995) examined the effect of isolated lumbar extension exercise
on 895 chronic low back pain patients who had failed an average
of six other treatment modalities prior to enrolling in the study.
The patients performed lumbar extension and torso rotation exercise
for 10 weeks. The results showed that most of the patients increased
low back strength, decreased low back and leg pain, and improved
their ability to perform daily activities. Seventy-two percent were
able to return to work.
Some evidence is also available suggesting that improving low back
strength is effective in reducing the incidence of low back dysfunction
in the work place. Mooney et al. (1995) reported that the prevalence
of low back injuries was reduced at a coal mine following a program
of 20 weeks of lumbar extension exercise.
BONE MINERAL DENSITY
Osteoporosis is a degenerative disease that is characterized
by a decrease in bone mineral density (BMD). This loss makes the
bones more susceptible to fractures. These fractures can lead to
decreased physical activity and possibly increased susceptibility
to further health problems and mortality. Research has indicated
that bone formation can be stimulated by placing a strain on the
bone as is seen during resistive and aerobic exercise (Rubin &
Lanyon, 1984). Although both forms of exercise can increase BMD,
the increase is site-specific to the joints exercised. Hamdy et
al. (1994) reported higher BMD in the upper arm in persons who weight
trained compared to runners, but that there was no difference for
lower body BMD between the two groups. Karlsson et al. (1993) reported
that active and retired weightlifters had higher BMD for the spine,
hip, tibia, and forearm when compared to controls. In a comparison
of BMD between female weightlifters, cyclists, cross-country skiers,
and orienteers, Heinonen et al. (1993) reported that the weightlifters
had the highest weight adjusted BMD in the distal radius, lumbar
spine, distal femur, and patella. Snow-Harter et al. (1992) showed
that eight months of either resistance exercise or jogging improved
lumbar BMD when compared to controls, but no difference was seen
between the exercise groups.
Braith et al. (1996) examined the effects of six months
of resistance exercise on BMD following heart transplant surgery.
Typically, BMD decreases during the post-operative period as a consequence
of glucocorticoid therapy. The group that performed strength training
for six months was able to return their lumbar, total body, and
femoral neck BMD to near baseline levels while the non-strength-training
groups BMD remained depressed.
Pollock et al. (1992) showed that six months of isolated
lumbar training improved lumbar BMD compared to controls in men
and women 60 to 79 years of age. Menkes et al. (1993) reported a
significant increase in femoral neck BMD in middle-aged to older
men following 16 weeks of strength training. These data indicate
that resistance and aerobic exercise can both positively affect
BMD, but that this influence is site-specific to the mode of exercise.
Exercise programs that emphasize endurance exercise usually
elicit a 1530% increase in maximum oxygen uptake (VO 2 max). Available
evidence indicates that traditional weight training (greater than
12 minutes rest between exercises) does not increase VO 2 max (Pollock
& Wilmore, 1990). However, it has been shown that performing
circuit training regimens can increase VO 2 max 58%. These regimens
consist of a circuit of approximately 10 exercises. A weight is
chosen that can be lifted for 15 repetitions for each exercise with
a short (1530 second) rest period between exercises. Thus, circuit
weight training has only a modest effect on VO 2 max and should
not be used for that sole purpose. Although weight training has
only a modest effect on VO 2 max, it has a dramatic effect on strength,
endurance, and physical function. For example, Hickson et al. (1980)
found that strength training the legs for 10 weeks improved performance
time on both a treadmill (12%) and a stationary cycle (47%), while
VO 2 max only increased 4%. Ades et al. (1996) reported that 12
weeks of strength training improved submaximal treadmill walking
time by 38% while no change was reported for controls.
Obesity is a risk factor for several health problems including
diabetes mellitus, arthritis, cardiovascular disease (CVD), and
kidney dysfunction (Stone et al., 1991). Also, due to excess nonmetabolically
active weight, an obese person has to expend more energy for movement
placing increased stress on the cardiovascular system. Aerobic exercise
has been widely prescribed and utilized as a means of weight control
and fat loss. There is also evidence indicating that strength exercise
is an effective means of influencing body composition. Gettman and
Pollock (1981) summarized the effects of five weight training and
six circuit weight training studies on changes in body composition.
The studies showed a mean decrease in body weight of 0.12kg, increase
in lean body mass of 1.5kg, and a decrease in fat mass of 1.7kg.
The added benefit of strength training to an aerobic exercise program
(caloric expenditure) is its effect on developing and maintaining
muscle mass and metabolic rate.
Metabolic rate decreases with age and a primary factor influencing
this decrease is reduced fat-free mass. Campbell et al. (1995) reported
that resting metabolic rate and energy intake required to maintain
body weight significantly increased in older adults following 12
weeks of strength training. These data are in agreement with Pratley
et al. (1994). Thus it appears that resistance exercise should be
a part of a well-rounded program including aerobic endurance exercise
for weight loss and controlling weight with age.
EFFECT ON CARDIOVASCULAR RISK FACTORS
There is growing evidence to indicate that strength training
may also be important to risk factor intervention. Strength training
exercise has been shown to increase insulin sensitivity, decrease
glucose intolerance, and has a modest effect on decreasing diastolic
blood pressure and may alter serum lipids.
Miller et al. (1984) reported that 10 weeks of strength training
significantly reduced basal insulin levels and area under the insulin
response curve following glucose ingestion. The decrease in insulin
was significantly correlated with increase in lean body mass. Hurley
et al. (1987) reported that insulin response to an oral glucose
tolerance test was significantly lower following 16 weeks of resistance
training. Smutok et al. (1993) compared the effect of endurance
and strength training on responses to a glucose tolerance test.
Both modalities decreased the total area under the curve for glucose
levels and insulin response, and there was no difference between
the two types of exercise.
Aerobic endurance exercise has been well established as a means
for favorably altering high density lipoprotein cholesterol (HDL-C).
The research concerning the effect of strength training is not as
clear and recent studies have produced conflicting results. Studies
that do show a positive result, typically involve higher volumes
emphasizing multisegment exercises.
Hurley et al. (1987) reported a 13% increase in HDL cholesterol
following 16 weeks of heavy strength training. Wallace et al. (1989),
and Johnson et al. (1982) both reported positive changes in lipid
profiles, but only during the highest volumes of training. Goldberg
et al. (1984) showed that a program emphasizing high volume with
short rest periods increased HDL while decreasing LDL and serum
triglycerides. Conversely, Kokkinos et al. (1987, 1991), Kohl et
al. (1992), and Smutok et al. (1993) all reported that strength
training did not significantly alter serum lipid profiles. Thus,
the available evidence seems to indicate that the type of exercise
performed by average strength trainers may not be sufficient to
impact serum lipids.
SAFETY AND PRACTICAL APPLICATION
Data regarding the safety of strength training and testing show
that it is safe if proper guidelines are followed. Gordon et al.
(1995) reported no adverse cardiovascular events following maximal
strength testing in 6,653 healthy men and women. Other studies have
shown no excess incidence of cardiovascular events using resistance
training compared to aerobic endurance training in varied populations.
Muscle soreness is common in beginning exercisers but significant
musculoskeletal injuries are rare. Persons with previous joint injuries
are at higher risk for sustaining an injury from strength training.
An important reason why strength training is beneficial in daily
life and may cause less risk in doing various lifting tasks is related
to the training effect. For example, McCartney et al. (1993) showed
that following 12 weeks of leg press training, maximal strength
increased 24%, and that blood pressure measured during submaximal
lifting decreased following the training period. Thus, strength
training can decrease the stress placed on the heart during lifting
tasks such as carrying groceries, snow shoveling, and lifting moderate
to heavy boxes, which have been implicated as a cause of heart attacks.
The effects of resistance/strength training on muscular strength
and endurance (muscle mass) and rehabilitation from musculoskeletal
injury is well known. As a result, most of the major health organizations
have included it as an important component of a well-rounded exercise
program along with aerobic endurance and flexibility exercise. More
recently, strength training has been shown to be beneficial in improving
many factors associated with good health. These factors include
increased function and prevention of falls, decreased pain in chronic
low back pain patients, improved glucose tolerance and insulin sensitivity,
increased BMD, increased basal metabolic rate (weight control),
and improved quality of life. Added long-term epidemiological studies
are necessary to confirm these findings. It appears that most of
the above findings can be attained in strength training programs
that include 810 exercises that are performed 23 days per week,
using 1 set of 815 repetitions to fatigue.