Download Physically Active Subjects Should Be the Control Group

INVITED COMMENTARY
Physically Active Subjects Should Be
the Control Group
FRANK W. BOOTH and SIMON J. LEES
Health Activity Center, Departments of Biomedical Sciences and of Medical Pharmacology and Physiology,
University of Missouri, Columbia, MO
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higher cardiovascular fitness are healthier relative to
sedentary/unfit individuals. From such information, The
U.S. Centers for Disease Control (CDC) identify physical
inactivity as an actual cause of disease (3). The CDC
published that heart disease and malignant neoplasm were
the two leading causes of deaths in the United States in
2000, whereas the two actual causes of deaths were
tobacco, then poor nutrition and physical inactivity (3).
Physically inactive lifestyles are an actual contributing
cause of Alzheimer’s disease, breast cancer, colon cancer,
coronary artery disease, obesity, osteoporosis, sarcopenia,
type 2 diabetes, and others (2). Therefore, physical
inactivity and chronic disease are not two separate
disciplines—they are inevitably linked, and this point
seems to have been underemphasized.
ost publications with a physical exercise group
use sedentary (physically inactive) subjects as
the ‘‘control’’ group. Our brief commentary will
contend an alternative approach based on the premise that
physically active individuals are healthier than sedentary
individuals, and therefore, the physically active subjects
should compose the control group.
The designation of sedentary subjects as ‘‘control’’ has
spontaneously happened without premeditated planning.
The control group at the beginning of the 1900s was
physical education students who were physically active
(Fig. 1). These physically active students undertook
additional exercise as the treatment group, approaching
the fitness level of elite athletes. Sedentary individuals
were likely rare in 1900, a time before automobiles,
industrial assembly lines with machines, computers, and
convenience technologies. During the next 100 years, the
treatment group of exercise remained the same, but the
control group went from physically active to sedentary.
Thus, controls for most exercise studies went from
physically active to sedentary during the 20th century.
Organizations such as the American College of Sports
Medicine have members who have contributed studies
proving that subjects with moderate physical activity/
Editor’s Note: In his 2005 Joseph B. Wolffe Memorial Lecture, Dr. Frank
Booth, one of ACSM_s most esteemed basic scientists, argued that
researchers studying physical activity effects on health-related outcomes
should adopt a new perspective when designing their studies. Dr. Booth’s
arguments were persuasive, passionate, and, merit our strong consideration. His perspective is summarized in this invited commentary.
FIGURE 1—Schematic for the proper designation of experimental
groups in 2006. In 1900, almost all individuals were physically active
in their daily lifestyles; further physical education students served as
controls for exercise studies (shown as the second highest activity state
in the closed horizontal box). In 1900, there were few, if any, ‘‘elite
athletes,’’ but exercise training moved physically active physical
education students toward the top physical activity state (top
horizontal line). In 2006, the majority of individuals have less than
30 min of physical activity each day, the generally agreed threshold
level for health benefits from physical activity; these individuals are
identified as ‘‘sedentary’’ (third activity state). The lowest shown
activity state is continuous bed rest (bottom horizontal line). In reality,
there is a spectrum of health and activity (up and down arrow to left)
states. Overtraining reduces health (suppressed immune system) in
the elite athlete (not shown).
Address for correspondence: Frank W. Booth, Ph.D., Department of
Biomedical Sciences, University of Missouri-Columbia, E102 Veterinary
Medical Building, 1600 East Rollins Road, Columbia, MO 65211; E-mail:
[email protected].
Submitted for publication November 2005.
Accepted for publication November 2005.
0195-9131/06/3803-0405/0
MEDICINE & SCIENCE IN SPORTS & EXERCISEÒ
Copyright Ó 2006 by the American College of Sports Medicine
DOI: 10.1249/01.mss.0000205117.11882.65
405
Copyright @ 2006 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.
Two professions use different criteria for assignment to
‘‘control.’’ The ‘‘control’’ group from the medical profession most often contains the healthier subjects, while the
‘‘control’’ group from the exercise profession usually has
unhealthier, sedentary subjects (Fig. 1). We believe that
when the sedentary group is used as the control group in
exercise studies it facilitates a misinterpretation that
exercise experts think sedentary individuals are healthy
enough, based upon the common designation in medical
journals that the control group is the healthy group.
The control/normal condition for the human genome for
hundreds of thousands of years was selective to environmental pressures, prominently from infrequent periods of
starvation and frequent sessions of moderate physical
activity (shown as the second physical activity level in
the enclosed box in Fig. 1). According to Neel_s Thrifty
Gene Hypothesis (4), genomes of many species were
‘‘fine-tuned’’ to efficiently store and utilize foods over
the ages. Since during the majority of human existence on
Earth, physical activity was a selective pressure on genes
for survival, genes were selected to perfect metabolism to
support physical activity.
Surprisingly in the absence of physical activity, inherited
metabolic pathways produce metabolic chaos (1). The
relatively recent (i.e., the last 100 years) dramatic decline
of physical activity from daily living has removed the
human genome from its expected frequent sessions of
moderate physical activity (shown as the sedentary activity
level in Fig. 1; (2)). The disorders that accompany
sedentary lifestyle are largely disorders of improper food
storage and utilization (atherosclerosis, obesity, type 2
diabetes). In contrast, physical activity causes ‘‘metabolic
health.’’ Therefore, physical inactivity and metabolic
disorders are inevitably linked as one.
Major questions in medical sciences should be those
that have the highest societal impact. A current major
question is ‘‘what causes chronic disease?’’; in many
cases, the actual cause can be largely attributed to physical inactivity. Therefore, the best game plan might be to
set up a research plan that is aimed at investigating the
actual cause(s) of chronic disease as it relates to physical
inactivity as the abnormal, unhealthy condition; healthier
physically active individuals should be assigned to the
control group.
REFERENCES
1. BOOTH, F. W., M. V. CHAKRAVARTHY, and E. E. SPANGENBURG.
Exercise and gene expression: physiological regulation of the human
genome through physical activity. J. Physiol. 543:399–411, 2002.
2. CHAKRAVARTHY, M. V., and F. W. BOOTH. Hot Topics: Exercise.
Philadelphia, PA: Hanley and Belfus (Elsevier), 2003.
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Official Journal of the American College of Sports Medicine
3. MOKDAD, A. H., J. S. MARKS, D. F. STROUP, and J. L. GERBERDING.
Actual causes of death in the United States, 2000. JAMA
291:1238–1245, 2004.
4. NEEL, J. V. Diabetes mellitus: a ‘‘thrifty’’ genotype rendered
detrimental by ‘‘progress’’? Am. J. Hum. Genet. 14:353–362, 1962.
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Copyright @ 2006 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited.