Friday August 17 2007
Increase the heart rate by running
Two sets of US guidelines have revised the public health advice on physical activity to clarify that gentle exercise is not enough to improve health, The Guardian reported. Current guidelines suggest that 30 minutes of exercise a day is enough to offer health benefits, however the newspaper said that adults “need to add jogging and twice-weekly weight-training sessions if they want to cut their risk of heart disease and obesity.”
The newspaper reports that “the lightest of activities such as dusting and the stroll to the car are being counted as exercise” and quotes the researchers as saying that people have “not accepted, and others have misinterpreted the original recommendation.”
The expert panel process and the recommendations offered have clarified some of the more unclear recommendations that were published in 1995. The group of experts met in 2000 to prepare this update, and this was supplemented by panel members’ own searches of the literature. It is not possible to validate the strength of evidence behind this policy advice.
Where did the story come from?
Two clinical practice guidelines were developed by an expert panel brought together by the American College of Sports Medicine and the American Heart Association. Separate writing groups contributed to each guideline but agreed to publish their recommendations together to avoid the risk of causing confusion.
The guidelines, called Physical activity and Public Health and Physical activity and Public Health in Older Adults, were published on the same date in the same edition of Circulation, the journal of the American Heart Association.
What kind of scientific study was this?
These clinical practice guidelines were developed through an expert panel process. The adult guideline panel included doctors, exercise scientists and public health experts. The older-adult guideline panel also included specialists in elderly medicine.
The adult panel “relied heavily” on a joint US and Canadian meeting that took place in 2000. At the meeting the relationship between the type, intensity and amount of physical activity and the health benefits was examined. The panel also conducted searches of the scientific literature, took into account other expert opinions, and looked at research on how best to communicate messages about physical activity. They classified the strength of their four main recommendations according to a system developed by the American College of Cardiology and the American Heart Association which reflected the strength of the underlying scientific evidence.
The older-adult panel of experts wrote background papers using their judgement for locating and analysing the relevant evidence; they did not undertake a full systematic review of the evidence. This process began in 2001. They have reviewed and tabulated the preventive and therapeutic recommendations from 11 guidelines published since 1999.
What were the results of the study?
The adult panel updated and clarified the 1995 recommendations on the types and amounts of physical activity needed by healthy adults to improve and maintain health.
The older-adult panel reviewed the existing consensus statements and relevant primary research for men and women over 65 years and those over 50 years with long-term medical conditions or limitations. They drafted a single recommendation, similar to that of the adult group, but with some differences. They suggested that advice for older adults should be more tailored to individual needs and planned to take into account prevention and treatment goals.
What interpretations did the researchers draw from these results?
The adult panel concluded: “To promote and maintain health, all healthy adults aged 18 to 65 years need moderate-intensity aerobic (endurance) physical activity for a minimum of 30 minutes on five days each week, or vigorous-intensity aerobic physical activity for a minimum of 20 minutes on three days each week.”
The panel suggested that combinations of moderate intensity activity (brisk walking that accelerates the heart rate) and vigorous intensity activity (jogging that substantially increases the heart rate and breathing) can be performed to meet this recommendation. Brisk walking that raises the heart rate, for 10 minutes at a time, can be accumulated toward the 30-minute minimum. In addition, every adult should also do activities that maintain or increase muscular strength and endurance on a minimum of two days a week. People may exceed these levels if they wish to further improve their personal fitness, reduce their risk for chronic diseases and disabilities or prevent unhealthy weight gain.
The older-adult panel concluded that the recommended intensity of aerobic activity take into account the older adult’s aerobic fitness. The panel also stated that activities to maintain or increase flexibility are recommended. For older adults at risk of falls, balance exercises are recommended. In addition, older adults should have an activity plan for achieving the recommended amount of physical activity that integrates their current preventive and therapeutic recommendations. The promotion of physical activity in older adults should emphasise moderate intensity aerobic activity, muscle strengthening activity, reducing sedentary behavior, and risk management.
What does the NHS Knowledge Service make of this study?
This is an important clarification of the recommendations, made by a distinguished group of experts with experience and knowledge in the field. The recommendations are more specific than the previous 1995 statement in terms of the intensity, duration and type of activity recommended. The addition of a specific recommendation on strength development and resistance training for adults and the promotion of flexibility, balance training and muscle strengthening activity in older adults is also referenced.
The evidence for benefit and particularly the degree of improvement in any measures of health to be expected in the different subgroups is not apparent from these recommendation documents. For example, it would be useful if the background evidence had been presented so that the reader could judge the degree to which the same recommendations can apply to sedentary, moderately active people or those athletes who are already fit.
The analysis of primary research that confirms the panels’ views on resistance training, the intensity of activity and the equivalence of 10-minute bouts of exercise may be made available in future publications.
Sir Muir Gray adds...
the current UK guidelines, the Chief Medical Officer has always recommended the need to walk briskly.
These updated US guidelines are a useful broadening in scope of the topic as often the term fitness focuses on one ‘s’: stamina. However there are three other ‘s’’s which should be considered: strength – which is covered by this paper – and skill and suppleness which these guidelines still do not cover, all of these are important in maintaining general health.