December 6 - 7, 2007 Advisory Committee Meeting
Adverse Events Subcommittee Report
Kenneth Powell, M.D., M.P.H., presented the subcommittee report
on adverse events. Adverse events are important because of two particular
reasons. One is that they provide a direct counter balance to any possible
benefits from physical activity. Additionally, adverse events can significantly
influence the level people participate in physical activity. The members of the
subcommittee included Julie Gilchrist from CDC, Bruce Jones from the U.S. Army,
Carol Macera from San Diego State, Paul Thompson from Hartford Hospital and
Susan Carlson was the groups CDC liaison. The subcommittee formulated the
What are the types of activities that have the lowest risk of
How does the amount or dose of physical activity affect these
Are individuals at higher risk of sudden adverse cardiac
events when they are being physically active?
What general factors influence the risk of musculoskeletal
injury and other adverse events related to physical activity?
Activities can be categorized by non-contact, activities with a fair amount of
contact and high-contact activities. As might be expected, the evidence suggests
that non-contact activities have the lowest risk of musculoskeletal injuries.
There are however, relatively few surveys from which to draw this conclusion.
Dr. Powell introduced Bruce Jones who addressed issues surrounding dose of
physical activity. The amount of exercise is determined by several parameters
such as duration, frequency, intensity and the total amount of activity is the
product of those parameters. It is important to recognize all the potential
parameters in determining total activity; otherwise, one may only see a partial
picture. Most of the studies pertaining to risk of injury deal with walking as
the activity, although there are a few studies that also include other
activities such as cycling. Also, many of the studies are older than the date
parameters of the CDC database. In reviewing the data the risks and benefits
both increase with increasing amounts of activity; however, the benefits plateau
at some level. Determining at what level the benefits plateau may be difficult
to determine due to individuals varying fitness levels. The more fit one gets
from training, the more tolerance one has for the activity without getting
injured. In order to minimize the risk while maximizing the benefits one should
avoid large increases in the amount of activity. The least active need to be the
most careful in initiating a program and sustaining a program.
Dr. Powell next discussed sudden adverse cardiac events. Seven reports in the
literature were found that deal directly with this issue. The data from these
reports suggest that participation in regular vigorous physical activity results
in a little boost in momentary risk; however, by and large, it is a considerably
lower risk than others that do very little physical activity. The slight boost
in risk occurs at the precise moments the heart is doing heightened work due to
Other issues surrounding adverse events include the few data sets available that
study the effects of moderate intensity activities. The Committee should closely
examine the importance of relative intensity. People who are less frequently
active and less frequently fit when doing the same thing, their relative
intensity is higher compared to individuals that regularly participate in
physical activity. Another issue that should be addressed is whether it helps to
consult a physician prior to launching into a fitness plan and does it matter
what category the individual is in such as, older adult, or what kind of
activity the individual plans to do such as moderate activity versus vigorous
activity. Body mass index is another important factor but there is too little
data to come to strong conclusions on its relationship to adverse events.
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