Aerobics vs. Resistance Training
Is This the Battle of the Fitness Titans?
Len Kravitz, Ph.D.
For years the virtues and values of aerobic exercise have been extolled and
celebrated while the benefits of resistance training have been minimized to that
of building muscles and improving sports performance. More recently, the
traditional perception of resistance training has undergone a revitalization due
to scientific evidence suggesting powerful health status betterment. In fact,
for those of you spending many a moment on the Internet, there are a lot of
voices out there in the ‘World Wide Web’ now chanting that resistance
training is the superior and only form of exercise you need. How the pendulum
has changed! The good news is that the evidence supports remarkable claims for
aerobics and resistance training for improvement in health. This battle of the
‘fitness titans‘ is attributable, unfortunately, to a blaring cluster of
uninformed individuals. Therefore, the purpose of this article is to provide
scientific evidence how resistance training and aerobic exercise are key
constituents of health, fitness and longevity (summarized in Table 1), and bring
to realization that including both of them in our physical activity programs
allows our students and clients to be the biggest winners.
Bone Mineral Density
Physical activities that stimulate bone growth need to include
progressive overload, variation of load, and specificity of loading (Conroy,
Kraemer, Maresh, & Dalsky, 1992) . Specificity of loading refers to
exercises that directly place a load on a certain region of the skeleton. With
osteoporosis, a degenerative disease characterized by a loss of bone mineral
density resulting in a susceptibility to bone fractures and health problems, it
appears resistance training and aerobic exercise may provide the needed stimulus
for bone formation (Rubin & Lanyon, 1984) . Progressive overload is
necessary so the bone and associated connective tissue do not exceed the
critical level that would place them at risk. In an eight-month study of
premenopausal women doing resistance exercise or jogging, bone mineral density
improved in both groups with no difference between groups (Snow-Harter, Going,
& Pamenter, 1995) . It appears that increases of bone mineral density are
site-specific. Hamdy et al (1994) reported greater increases in bone tissue in
the upper arm of resistance trained subjects as compared to runners, although
both groups showed similar changes in the lower body. Exercise programs to
increase bone growth should be full-body in nature, including exercises such as
squats and lunges which direct the forces through the axial skeleton and allow
greater loads to be utilized (Conroy & Earle, 1994) . In addition, evidence
does suggest that moderate weight-bearing activity, such as brisk walking done
regularly, and for a long-term basis, is effective in averting age-related bone
loss (Vuori, 1995)
.
Hypertension
Hypertension is a major health problem. Elevated systolic and diastolic
blood pressure is associated with a higher risk of developing coronary artery
disease (CAD), congestive heart failure, stroke, and kidney failure. There is a
onefold increase in developing these diseases when blood pressure is 140/90 mmHg
(Bouchard & Despres, 1995) . It is necessary for the fitness professional to
also educate clients that reducing weight and lowering alcohol and salt intake
may help reduce elevated blood pressure in many cases. Intervention studies have
shown that regular aerobic activity can reduce systolic and diastolic blood
pressure by approximately 10 mmHg (Hagberg, 1990) . Also, moderate-intensity
exercise (40%-70% of VO2max) tends to produce greater decreases in resting blood
pressure than higher intensity exercise. Although regular aerobic exercise will
not likely affect normotensive individuals, habitual aerobic exercise may be
protective against the increase in blood pressure commonly seen with increasing
age (Blair, Goodyear, Gibbons, & Cooper, 1984) .
During resistance exercise, systolic and diastolic blood pressures may show
steep increases, which indicates that caution should be observed with persons
with known cardiovascular disease or risk factors (Stone, Fleck, Triplett, &
Kramer, 1991) . These increases in blood pressure are dependent on the intensity
of the contraction, the length of time the contraction is held, and the amount
of muscle mass involved in the contraction (Fleck, 1988) . More dynamic forms of
resistance training, such as circuit training, that involve moderate resistance
and high repetitions with short rests are associated with reductions in blood
pressure. Studies have shown decreases in diastolic blood pressure (Harris &
Holly, 1987) , no change in blood pressure (Blumenthal, Siegel, & Appelbaum,
1991) , and decreases in systolic blood pressure (Hagberg et al., 1984; Hurley,
Hagberg, & Goldberg, 1988) . More research is necessary to clearly
understand the role of resistance training in blood pressure management.
Resting Heart Rate
In terms of chronic adaptations, there appears to be a reduction in heart
rate from resistance training, which is considered favorable (Stone et al.,
1991) . Long term adaptations observed in the research show from no change up to
a 11% decrease in heart rate, which may be explained by the differences in
intensity, volume, rest between sets, use of small vs. large muscle mass,
duration of study and fitness level of the subjects.
Regular participation in aerobic exercise often results in a decrease in resting
heart rate by 5 to 25 beats per minute. The lowered resting heart rate from
exercise training is proposed to be due primarily to an increase in the
parasympathetic nervous activity with a minor decrease in sympathetic nervous
discharge (Katona, McLean, Dighton, & Guz, 1982; Smith, Hudson, Graitzer,
& Raven, 1989) .
Blood Lipids and Lipoproteins
It is well-established that low plasma triglycerides, total cholesterol,
and low-density lipoprotein cholesterol (LDL-C) levels, as well as elevated
high-density lipoprotein cholesterol (HDL-C) levels, are associated with a
lowered CAD risk. Regular aerobic exercise has been shown to lower blood
triglycerides in individuals with initially high levels, with no influence on
persons with normal concentrations. All intensity (low, medium, high) levels of
aerobic exercise have shown increases in HDL-C, particularly the HDL2
subfraction, as well as favorably altering total cholesterol and LDL-C (Bouchard
& Despres, 1995) . The commonality seen in endurance exercise programs that
positively affects blood lipid profiles is that the training creates a
substantial negative energy balance (Despres & Lamarche, 1994) .
Although several studies have shown favorable impact of resistance training on
blood lipids, several others have reported no change. It has been suggested that
the resistance programs that best modify blood lipid profiles incorporate larger
muscle mass, multi-segment exercises with a high total volume (reps x sets x
load) prescription (Stone et al., 1991) . Additional research needs to be
conducted which controls for body composition changes, day-to-day variations in
lipoproteins, dietary factors, and possible other training adaptations to
provide a more credible summary of the effect of resistance training on blood
lipids and lipoproteins.
Glucose Metabolism
Elevated insulin and blood glucose levels are characteristic features
involved in the development of non-insulin-dependent diabetes mellitus, which
develops primarily in adult women and men who are overweight and have excess
abdominal fat tissue. One of the benefits of aerobic exercise is the improvement
of the sensitivity of liver, skeletal muscle and adipose tissues to insulin
action. A decrease in blood plasma glucose in hyperglycemic individuals is also
see with chronic aerobic activity. There is very persuasive evidence, from three
large studies, that regular aerobic activity actually plays a substantial role
in maintaining normoglycemia and insulin sensitivity in nondiabetic individuals
(Bouchard & Despres, 1995) .
Improvements in glucose metabolism with strength training, independent of
alterations in aerobic capacity or percent body fat, have also been shown
(Hurley et al., 1988; Smutok, Reece, & Kokkinos, 1993) . Smutok et al.
(1993) concluded that strength training and aerobic training improved glucose
tolerance and reduced insulin responses to oral glucose (in men) similarly. It
appears that both resistance training and aerobic exercise offer a strong
protective role in the prevention of non-insulin-dependent diabetes mellitus.
Cardiorespiratory Fitness
Numerous controlled training studies have tested for the effects of
intensity, duration and frequency of aerobic exercise on maximal oxygen uptake
(VO2max). A minimum of 20 minutes of aerobic exercise at 50% or more of the
individual’s VO2max, on three or more days per week, will produce a 10% to 20%
increase in VO2max in most sedentary persons (ACSM, 1995) . The literature
thoroughly supports the evidence that exercise intensity is directly related to
the change in VO2max (Gossard et al., 1986) . Higher doses of aerobic exercise
produces greater increases in VO2max, although these improvements are not
proportionately greater.
Traditional resistance training that employs sets followed by 1 to 2 minutes of
rest has not shown an increase in VO2max. Studies have shown little to mild
improvement in aerobic capacity (5% to 9.5%) from participation in circuit
weight training (Kass & Castriotta, 1994; Peterson, Miller, Quinney, &
Wenger, 1988) . Kass and Castriotta suggest that the mild increases in aerobic
capacity are due primarily to increases in fat-free mass from the circuit weight
training, and not changes from the main factors affecting aerobic capacity:
cardiac output (heart rate x stroke volume) or arterial-venous oxygen difference
(exchange of oxygen and carbon dioxide at the cellular level).
Body Composition
A negative energy balance generated by cardiorespiratory activity,
instead of reduced caloric intake, and sustained for several months has been
shown to result in weight loss that is predominantly attributable to a loss of
body fat (Bouchard & Despres, 1995) . In contrast, when the negative energy
balance is caused by lower energy intake (through diet alone), one also loses a
significant amount of lean tissues, which may be as much as 50% of the total
weight loss (Tremblay, Despres, & Bouchard, 1985) .
Resistance training and circuit training studies have shown decreases in body
weight and fat mass with comparable increases in fat-free mass (Gettman &
Pollock, 1981) . One of the noteworthy benefits of resistance exercise, as it
relates to weight loss, is the positive impact of increasing energy expenditure
during the exercise session and on maintaining, or increasing, fat-free body
mass while encouraging the loss of fat body weight (Young & Steinhard, 1995)
. An impressive finding to highlight with resistance training is that the energy
expenditure following higher total volume workouts appears to be elevated, with
an increase in fat utilization (due to a lower respiratory exchange ratio)
during this period (Melby, Scholl, Edwards, & Bullough, 1993) . The evidence
unequivocally supports the combined use of aerobic exercise and resistance
training for optimal changes in body composition to successfully attain weight
management goals.
Resting Metabolic Rate
The largest single source of energy expenditure is the resting metabolic
rate, which is defined as the energy necessary to maintain the body’s
physiological systems at rest. It is accountable for 60% to 75% of the daily
energy expenditure and closely associated to the fat-free body mass. Some
researchers have shown that resting metabolic rate may be influenced by aerobic
exercise training while others have failed to show a difference. Tremblay et al
(1985) measured resting metabolic rate in untrained, moderately trained (6-10
hrs of vigorous exercise weekly) and highly trained (12-16 hours of vigorous)
young males. Results showed that the relative resting metabolic rate was
significantly increased in the highly trained subjects, while no difference was
seen between the moderately trained and untrained subjects. It has been
suggested that this increased resting metabolic rate, observed in high-intensity
aerobic endurance training, may be a result of an increased energy intake and
expenditure (high caloric turnover) and other accumulative factors due to
intensity, duration and frequency affecting post-exercise energy expenditure
(Van Zant, 1992) .
Several studies, with adult men and women of various ages, have demonstrated
significant increases in lean body mass which has been shown to increase resting
metabolic rate (Pratley et al., 1994). The key factor seen in the training
programs appears to be the total volume of training using the major muscle
masses of the body (Stone et al., 1991).
Musculoskeletal Health
Muscle mass, strength, power and endurance are all important for the
prevention of several diseases, injuries and the improvement of movement
capabilities. Although these components of musculoskeletal health show
substantial decreases with age, it has been suggested that this is due largely
to a decrease in physical activity, and not solely age (Bassey & Harries,
1993) . This decrease in strength is linked to decreased mobility and increased
risk of falling, which has been identified as the most frequent cause of injury
related to mortality (Pollock, Vincent, Corbin, & Pangrazi, 1996) .
Substantial improvement in all of the components of musculoskeletal health, as a
result of resistance training, have been shown in sedentary, disabled, young,
physically active, and very old frail individuals (Vuori, 1995) .
Functional Capabilities
Functional capabilities can be defined as the ability to perform basic
physical actions such as walking, climbing stairs, reaching, stooping, bending
and grasping, which are fundamental components of daily living. Experimental and
observational research show that aerobic exercise and resistance training
contribute to the maintenance of functional capabilities during aging (Buchner,
Beresford, Larson, LaCroix, & Wagner, 1992; Wagner & Lacroix, 1992) .
Also, comprehensive programs for the improvement of low back health include
aerobic exercise and muscular fitness exercises (Plowman, 1992) .
Longevity
Estimates of the extension of life comparing men who
expended&Mac179;2,000 kilocalories per week in physical activity, including
walking, recreational activities and stair climbing, to men who expended <500
kilocalories per week in similar activities, for over 16 years, found the active
men to live upwards of two years longer (Paffenbarger & Lee, 1996) . This
difference held after controlling for cigarette smoking, body weight,
hypertension, and age. Similarly, with regular walking, cycling and
cross-country skiing as the activity variables of interest (and then
standarizing for age, systolic blood pressure, cholesterol, and body mass),
researchers in Eastern Finland showed that active men live an extra 2.1 years
when compared to their inactive counterparts, during a 20-year study (Paffenbarger
& Lee, 1996) . Indeed, a convincing relationship exists between
moderate-intensity physical activity and longevity.
Directions for the Future
Numerous health and fitness benefits have been documented for both
resistance training and aerobic exercise. If health and fitness professionals
prescribe to the new expanding model of ‘physical activity for the enhancement
of health,’ it is clear that program prescriptions need to include resistance
training and aerobic exercise. With the merging of the computer and
communication technologies, broad access to the Internet and World Wide Web will
be more available and affordable. This presents new opportunities and challenges
for health professionals. More education and information about health, fitness
and longevity will be easier to disseminate to an interested, growing audience.
However, one impact is clear, with more time spent on a computer, people may
find it harder to find time for physical activity. Instead of debating the pros
and cons of aerobic vs. resistance training, perhaps we as a profession should
focus now on how to best design optimal workout programs for the demands of the
next century.
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