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Physical Activity Guidelines

February 28 - 29, 2008 Advisory Committee Meeting Minutes

Subcommittee Report: Adverse Events

Kenneth Powell, M.D., M.P.H., led discussion on the subcommittee report on adverse events. The subcommittee focused primarily on musculoskeletal outcomes with a secondary focus on sudden adverse cardiac events. The group also acknowledged issues related to heat and cold related injuries, motor vehicle collisions, infectious diseases and other events.

Major questions addressed by the subcommittee included:

  1. What type of activity has the lowest risk of musculoskeletal injuries?  These activities included non-contact, limited contact, contact and collision type activities.

    Conclusion
    The interpretation of the data seems to conclude non-contact and limited contact activities such as walking, swimming, dancing and golf had the lowest risk of musculoskeletal injuries.

  2. How does the dose of physical activity affect the risk of musculoskeletal injury?

    Conclusion
    All components of dose such as frequency, duration and intensity are directly related to risk.

  3. What general factors influence the risks of musculoskeletal injury and other adverse events related to physical activity?

    Conclusion
    Many, but current physical activity or fitness factors have solid evidence and injury prevention potential.

  4. Are people at higher risk of sudden adverse cardiac events when they are being physically active?

    Conclusion
    Yes, but being physically active reduces risk during the activity and overall.

Dr. Powell noted that risk of adverse events is proportional to the gap between accustomed levels of activity and activity at a particular moment. Due to the fact that those most in need of activity are also at the greatest risk the idea of training progression is important. During activity there is a recovery gap in between the beginning of the activity and the time the body adapts. Breaking these gaps into smaller periods allowing for adaptation should help avoid breakdowns. Tissue and organ function improves after repeated cycles of overload, recovery, and adaptation.

Data suggests walking and short bouts of activity are helpful for inactive individuals beginning an exercise program such as walking 5 – 15 minutes 2 – 3 times per week. For subsequent increases of activity adaptation among unfit and elderly people requires weeks of recovery. Small incremental increases should be in the range of 5 – 15 minutes every 3 – 4 weeks. Also, increases in frequency and duration should take place before increases in intensity.

Regarding the issue of obtaining a participation clearance from a medical or health professional there is no empirical information that clearances are beneficial. It is common in men over 40 years of age, women over 50 years of age, people with chronic disease and people with risk factors for chronic disease to consult with a health professional prior to beginning a physical activity program. While it may be common sense to recommend consulting with a health professional it may also be a barrier to participation by implying a certain activity is more dangerous then being inactive. Dr. Powell discussed the following suggested chart:

Suggested health evaluation by population group and intensity of physical activity

Population Light to moderate PA Vigorous PA
Children, youth and young adults Follow school requirements Follow school requirements
Healthy people Not necessary Not necessary
People at risk Not necessary* Develop a plan with health care provider

*Assumes the increase in light to moderate intensity activity is prudent (e.g., 5 – 15 minutes of walking 2 – 3 times per week) and increases by small amounts at adequately spaced intervals (e.g., every 3 – 4 weeks).

 

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