2008 Physical Activity Guidelines for Americans - Funding Opportunities & Research Resources for Researchers
The Federal Government has issued its first-ever Physical Activity Guidelines for Americans.
They describe the types and amounts of physical activity that offer substantial health
benefits to Americans. Accompanying the guidelines is an Advisory Committee
Report that reviewed existing scientific literature to identify evidence to develop
the physical activity recommendations. Although a substantial amount of research on
physical activity and health has been published since 1995, major gaps still exist in our
knowledge needed to establish cause and effect for various health outcomes and to better
define dose response, especially at the low and high ends of the activity spectrum. These
gaps are highlighted in Part H: Research
Recommendations in the Advisory Committee Report.
The following presents the Research Recommendations from the report. For each topic
area, we have highlighted relevant NCI and NIH funding opportunities for researchers who
wish to explore these remaining gaps in the scientific evidence. Also listed are links
to information about surveys, databases, and other NCI and NIH research resources that
could help answer specific research questions under several of the topic areas.
- Some recently published data indicate that physical activity of a lower intensity
and/or smaller amount than is currently recommended may provide significant health
benefits for chronically inactive or unfit adults (who comprise a large proportion of the
American population aged 18 years and over) and older adults. Both experimental and
observational studies are needed to answer a variety of questions about the nature of
benefits provided and characteristics of dose required at the low end. The range of
physical activity used in the intervention should include a dose below that currently
identified in physical activity recommendations to evaluate its impact and the stability
of this level of physical activity behavior over time.
- There remains a lack of data defining both the shape of the dose-response curve at
the higher amounts and intensities of activity for most health outcomes and whether an
upper limit of benefit exists. Most current recommendations focus on a minimal or target
amount/intensity of activity that is consistent with much of the population receiving some
benefit, but don't address questions of "optimal" or "maximal" benefit. Studies are need
to clarify the amount of physical activity, defined by metabolic equivalent (MET)-minutes
per week or some other measure, at which additional improvements in various health
outcomes no longer occur or at which increases are negated by increased adverse medical
- To fill the gap in our knowledge about dose response, investigators should design and
conduct studies that evaluate effects of the following variables at fixed volumes of
physical activity: intensity, frequency, duration, and multiple bouts. Details related to
these variables would allow more precise physical activity guidelines to be developed
across the breadth of activity-related health outcomes.
- Reasonable evidence exists that activity accumulated in short bouts throughout the
day can favorably alter selected biomarkers for cardiovascular and metabolic diseases and
improve cardiorespiratory fitness. However, no evidence is available that such patterns of
activity may be beneficial for musculoskeletal health. Experimental studies are needed to
extend this research involving activity bouts of different durations, especially multiple
bouts shorter than 10 minutes and a few long bouts per week (e.g., 2 x 75 minutes) on
various health outcomes. Observational studies are needed using assessment methodologies
that will allow accurate quantification of a range of types of activity in different
population groups (e.g., abdominally obese, frail elderly) and an evaluation of the effect
of accumulation of short bouts on clinical outcomes independent of activity intensity and
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- Additional large scale, multi-site RCTs are needed to more thoroughly characterize
the dose response of physical activity on weight stability, weight loss, and body
composition across a variety of population groups, especially for those in the normal body
mass index range. Only a limited number of RCTs have addressed these outcomes. Large-scale
multi-site RCTs would allow investigators to more effectively address issues related to
susceptibility to weight gain or resistance to weight or fat loss that may vary by sex,
race/ethnicity, and age. As mentioned in the overarching recommendations, various volumes
should be evaluated within the same study design.
- Determine the most effective strategies for promoting and maintaining sufficient
doses of physical activity to facilitate weight loss and/or weight stability. It is
important to develop effective intervention strategies to promote and maintain the desired
level of physical activity for weight loss and/or weight stability because adherence to
this level of physical activity is currently less than optimal. Although some strategies
have been shown to be effective for improving adherence to this level of physical
activity, the success of these strategies has been demonstrated in limited samples and
populations. Therefore, additional research in this area is needed.
- Determine how much physical activity is needed to prevent weight regain following
weight loss. Most of the available literature related to this question is observational or
has relied on retrospective analysis of self-selected and self-reported levels of physical
activity. Use of state-of-the art technology and complete energy balance designs are
absent from the literature. Specifically, it appears that no adequately powered studies of
sufficient duration with randomization have been conducted to examine different levels of
physical activity following weight loss.
- Determine the physical activity effects on total and regional fat loss from those of
weight loss, per se, especially in those people very susceptible to weight gain in the
current social environment and who thus may be most resistant to weight or fat loss with
exercise. Additional RCTs are needed to distinguish physical activity effects from weight
loss effect. In addition, the large-scale use of imaging techniques is necessary to
distinguish between subcutaneous and visceral fat depots in their responsiveness to
endurance and/or resistance training. The ability of studies to translate imaging findings
into simple anthropometric measures such as the waist or the abdominal circumference would
increase the clinical and personal utility of the research.
- More research is needed to establish the risks and benefits of various regimens of
physical activity in men and women with a body mass index of 35 or greater.
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- Knowledge about the role of physical activity in reducing the risk of common cancers
would benefit from additional evidence gathered from clinical trials. In the survivorship
setting, clinical trials showing a benefit of physical activity interventions on reducing
deaths, recurrences, and reducing the impact of late or long-term treatment effects also
would make a valuable contribution to our understanding of the needs of this growing
- Studies are needed to clarify biological mechanisms linking physical activity to
specific cancers in order to identify associations with less commonly studied cancers.
- Studies are needed to define the shape of the dose-response curve of the physical
activity-cancer relation in order to determine the effect of low-intensity activities and
- Observational epidemiologic research is needed to identify the dose, type, and
frequency of physical activity on risk of various cancer sites and subtypes, in addition
to identifying the effect of physical activity on risk of specific cancers within
particular population subgroups, including various races and ethnicities, ages, sexes, and
groups at elevated risk of cancer.
- Studies of Energy Balance and Cancer in Humans
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- Determine whether physical activity affects classroom behavior and academic
achievement in children and adolescents.
- Determine whether physical activity affects depression, anxiety, and cognitive
function in children and adolescents.
- Determine the types and amounts of physical activity that are needed to prevent the
development of excessive adiposity during childhood and adolescence.
- Identify the optimal types and amounts of physical activity needed to maintain
cardiorespiratory and metabolic health during childhood and adolescence.
- Establish the dose-response pattern for the relation between physical activity and
bone health in children and adolescents.
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Participant Diversity & Racial/Ethnic Diversity
- An increased number of Federally-funded studies should be powered to include
sufficient representation of at least one ethnic/minority or lower SES population, with
sufficient sample size to permit subgroup analyses by race/ethnicity or SES. Strict
exemption criteria should be rigorously applied.
- Cultural proficiency of recruitment and retention approaches and adequacy of
resources directed toward recruitment and retention should be scrutinized by grant review
committee members with special expertise in this area, similar to the separate assessments
of adequacy of study methods and analytical approaches by review committee statisticians.
- Federal program officers should manage and balance their portfolios to ensure that
racial/ethnic differences in physical activity-related exposures and outcomes are under
active investigation, and should use requests for applications (RFAs) and other mechanisms
to direct funding toward disparities examination and elimination.
- Journals should require reporting of race/ethnicity, sex, and SES of samples in the
abstract as well as the body of the text.
- Subgroup analyses should be requested when sample size is sufficient, and further
data desegregation should be encouraged to examine interactions between sociodemographic
characteristics, e.g., sex-ethnicity, SES-ethnicity.
- Abstraction databases should include search criteria that permit ascertainment of
inclusiveness (i.e., subgroup analyses by race/ethnicity or SES).
- Specific research questions deserve particular emphasis, such as the precise role in
weight maintenance of racial anthropomorphic variations in resting or activity-related
energy metabolism (as opposed to or in concert with age- or sex-related differences) in
- Journal standards for peer-reviewed articles should require a reporting of the
race/ethnicity (in addition to sex and age) of the sample and presentation of subgroup
analyses by race/ethnicity and/or SES if sample sizes are sufficient, rather than simply
treating these as co-variates and adjusting for them.
- Research on the Economics of Diet, Activity, and Energy Balance
- Health Promotion Among Racial and Ethnic Minority Males
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- Uniform data collection is needed with respect to the type of physical activity
(e.g., leisure-time, occupational) and physical activity characteristics (e.g., intensity,
- The Compendium of Physical Activity has been very useful in assigning standardized
values of absolute intensity to a wide range of activities, but it should be updated and
expanded to children and youth.
- During the past decade, technology that provides for the objective assessment of
physical activity in relatively large groups of subjects has increased rapidly, especially
through the use of motion sensors and physiological monitoring. These technologies have
the potential to greatly improve the accuracy and reliability of physical activity
assessment in free-living populations leading to a better understanding of health benefits
and dose response. Development and evaluation of these technologies are needed for
assessing populations with different activity profiles and sociodemographic
- A much better understanding is needed on how the results of physical activity
assessed by new objective measurement methods can be compared to data collected by
commonly used questionnaires.
- Because of the scientific and logistical challenges of including adequate-sized
samples of multiple groups in a study conducted at one institution, well-designed and
executed multi-center studies are needed in which each research site can have access to
subjects who represent various specific understudied populations. This is critically
important in providing investigators with opportunities to examine interactions between
sociodemographic factors, particularly sex and race/ethnicity or SES, and physical
activity in relation to health and to make inter-group comparisons.
- Funding agencies should support well-designed studies of individual understudied
populations, especially race/ethnic minorities, persons of low SES, and individuals with
physical and cognitive disabilities, so that major questions regarding the effects of
exercise and effectiveness of physical activity interventions in each of these populations
can be answered. If an organization funded a number of such studies with at least a core
of shared measures, they would have a well-diversified research portfolio on understudied
populations. Such an approach would more likely answer key questions than would an
approach that requires each investigator to include relatively small numbers of
understudied populations in their studies.
- Improving Diet and Physical Activity Assessment
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Physical Activity and Physical Fitness Surveillance
- Surveillance of the total activity energy expenditure of representative samples of
the US population needs to be implemented once appropriate assessment tools have been
developed and validated. Such tools could include either questionnaires or new objective
measurement technology, or a combination of the two.
- Special attention needs to be given to the surveillance of both the physical activity
and physical fitness of the US population at both ends of the age spectrum --
toddlers/children and the oldest adults. These groups constitute a substantial portion of
the US population and receive unique benefits from being physically active, but no
national surveillance system for physical activity or physical fitness data exist for
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Systematic Reviews and Meta-Analyses
- Experts investigating specific health outcomes from physical activity should assess
the nature and volume of recent publications and determine whether quantitative reviews of
the data would contribute to existing knowledge, help formulate guidelines and policy
statements, and help set research priorities.
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