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• Response to Tammy M Vehige et al.
  John W G Yarnell
  Published on: 23 November 2015
• Response to Dr Buckley
  John W G Yarnell
  Published on: 23 November 2015
• Some key weakness in this study
  J P Buckley
  Published on: 23 November 2015
• Author's response
  John W G Yarnell
  Published on: 23 November 2015
• General Exercise Recommendation
  Tammy M Vehige
  Published on: 23 November 2015
• Lowering CVD risk: walk before we run
  Michael J. LaMonte
  Published on: 23 November 2015

• Published on: 23 November 2015

  Response to Tammy M Vehige et al.

  • John W G Yarnell, Reader

  Dear Editor

  In response to Tammy Vehige et al,[1] we had recognised that our findings may be controversial, but these were rigorously evaluated by ourselves and others before publication. However, to put it in context, it is one study amongst a particular population of healthy, middle-aged men of whom about 40% appeared to be doing enough vigorous intensity activity to confer cardiovascular benefit. The pape...

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  Dear Editor

  In response to Tammy Vehige et al,[1] we had recognised that our findings may be controversial, but these were rigorously evaluated by ourselves and others before publication. However, to put it in context, it is one study amongst a particular population of healthy, middle-aged men of whom about 40% appeared to be doing enough vigorous intensity activity to confer cardiovascular benefit. The paper itself urges caution in extrapolating the findings to other populations, but recommends that the findings should be rigorously checked in other similar studies.

  Reference

  (1) Vehige TM et al. General Exercise Recommendation [electronic response to Yu S et al. What level of physical activity protects against premature cardiovascular death? The Caerphilly study] heartjnl.com 2003 http://heart.bmjjournals.com/cgi/eletters/89/5/502#150

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  Conflict of Interest:
  None declared.

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• Published on: 23 November 2015

  Response to Dr Buckley

  • John W G Yarnell, Reader

  Dear Editor

  In response to Dr Buckley [1] we agree that data on cardiovascular fitness would have been a useful addition to our study but resources in terms of staff and equipment precluded this possibility. In an ideal study, both cardiovascular fitness and questionnaire data would be obtained in parallel and in a long term cohort study habitual physical activity should be re-assessed at intervals.

  Refer...

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  Dear Editor

  In response to Dr Buckley [1] we agree that data on cardiovascular fitness would have been a useful addition to our study but resources in terms of staff and equipment precluded this possibility. In an ideal study, both cardiovascular fitness and questionnaire data would be obtained in parallel and in a long term cohort study habitual physical activity should be re-assessed at intervals.

  Reference

  (1) Buckley JP. Some key weakness in this study [electronic response to Yu S et al. What level of physical activity protects against premature cardiovascular death? The Caerphilly study] heartjnl.com 2003 http://heart.bmjjournals.com/cgi/eletters/89/5/502#154

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  Conflict of Interest:
  None declared.

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• Published on: 23 November 2015

  Some key weakness in this study

  • J P Buckley, Exercise Physiologist

  Dear Editor

  I couldn't help but sit up and take notice of the news this morning, which made reference to this paper on physical activity and heart disease.[1] Obviously the news reporters are free to say what they like but I am concerned about some key weakness in this study, which has let the press loose on stating that brisk walking does not help prevent heart disease. It is well known and accepted practice within spo...

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  Dear Editor

  I couldn't help but sit up and take notice of the news this morning, which made reference to this paper on physical activity and heart disease.[1] Obviously the news reporters are free to say what they like but I am concerned about some key weakness in this study, which has let the press loose on stating that brisk walking does not help prevent heart disease. It is well known and accepted practice within sports medicine and exercise science to describe exercise intensity in terms relative to an individual's level of fitness and not in absolute terms. The Yu paper only described the activity indexes in absolute terms and thus we have no idea what proportion of the individual participants' aerobic capacity was being challenged in the low to moderate activity categories.

  A recent meta-analysis by P Williams [2] did confirm from the evidence that higher intensity aerobic fitness promoting activity, provided greater prevention of CHD and CVD than did lower to moderate habitual physical activity but that the latter still had a profilactic effect on CHD/CVD. Furthermore, the work done by Professor Hardman's group and colleagues at Loughborough showed that in middle aged women, brisk walking did result in enhancing aerobic fitness as well as well as improving healthier levels of serum cholesterol both of which would provide CHD protection.

  I was greatly disappointed to see that with much medical screening of the subjects in the Yu et al. study that they left out an all important fitness test, which is paramount in determining the "intensity threshold" at which improvements take place. It is quite wholly possible that for many, the habitual physical activity described in absolute terms of intensity may not elicit a level above a training threshold (e.g. 50% of VO₂ max). Aerobic capacity is greatly a function of genetics and gender (which can be independent of levels of physical activity).

  As this study was only done on males, and females tend to have lower aerobic capacities, then this makes for a second weakness of the study; it leaves out 50% of our population. For the unfit person brisk walking may well reqiure the participant to utilise more than 50% of their aerobic capacity, which would thus fit into the moderate to higher intensity exercise zone that can lead to a training effect and these are the people in most need of taking up the Government's physical activity initiatives. Therefore, without a description of fitness in the Yu et al. study, we are left with a very big question mark over the differentiation of exercise intensities (Activity Indexes), which were defined.

  References

  (1) S Yu, J W G Yarnell, P M Sweetnam, and L Murray. What level of physical activity protects against premature cardiovascular death? The Caerphilly study. Heart 2003;89:502-506.

  (2) Williams PT. Physical fitness and activity as separate heart disease risk factors: a meta-analysis. Med Sci Sports Exerc 2001;33(5):754-61.

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  Conflict of Interest:
  None declared.

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• Published on: 23 November 2015

  Author's response

  • John W G Yarnell, Reader

  Dear Editor

  In reply to Michael LaMonte et al.[1]:

  1. The questionnaire was modified only in relation to differences in American and British sports, for example in Britain softball, paddle ball and raquet ball are rarely played and there is very little hunting for large game. We included some activities such as mixing cement and we used approximate equivalents for this activity using a mixer or...

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  Dear Editor

  In reply to Michael LaMonte et al.[1]:

  1. The questionnaire was modified only in relation to differences in American and British sports, for example in Britain softball, paddle ball and raquet ball are rarely played and there is very little hunting for large game. We included some activities such as mixing cement and we used approximate equivalents for this activity using a mixer or at a higher intensity if done by hand. In particular we did not downgrade any high intensity codes to moderate intensity codes.

  2. The vigorous activity was usually done on top of light and moderate intensity activity as Table 3 in the paper makes clear. The trends for the total activity are significant, particularly for CHD.

  3. We combined light and moderate activity only to reduce the number of tables to 6 instead of 7 as the separate tables showing light or moderate activity showed no trend whatsoever with increasing activity and mortality.

  4. Trends were examined with both thirds and fifths of distribution separately for light and moderate intensity activity and no trends were detected.

  Reference

  (1) LaMonte MJ, Adams TD, Yanowitz FG. Lowering CVD risk: walk before we run [electronic response to Yu et al. What level of physical activity protects against premature cardiovascular death? The Caerphilly study] heartjnl.com 2003 http://heart.bmjjournals.com/cgi/eletters/89/5/502#153

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  Conflict of Interest:
  None declared.

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• Published on: 23 November 2015

  General Exercise Recommendation

  • Tammy M Vehige, Program Manager, Physical Activity
  • Other Contributors:
    • Stephanie Fulton, Thomas Wilding, Frances Groen

  Dear Editor

  Recently a reporter from the Arizona Republic wrote an article that cited your study[1] on vigorous exercise. The author stated that "a half-hour brisk walk every day may make you feel better, but it is not enough to ward off premature death from heart trouble."

  As a public health specialist it concerns me that we are sending mixed messages to the public. In the United States approximately 60% of...

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  Dear Editor

  Recently a reporter from the Arizona Republic wrote an article that cited your study[1] on vigorous exercise. The author stated that "a half-hour brisk walk every day may make you feel better, but it is not enough to ward off premature death from heart trouble."

  As a public health specialist it concerns me that we are sending mixed messages to the public. In the United States approximately 60% of the population is not even getting 30 minutes of moderate physical activity. If we tell them that only vigorous activity counts (keeping in mind that they are not doing moderate activity), is it realistic to think that they are going to do vigorous activity?

  I would appreciate any comments the authors may have.

  Reference

  (1) S Yu, J W G Yarnell, P M Sweetnam, and L Murray. What level of physical activity protects against premature cardiovascular death? The Caerphilly study. Heart 2003; 89:502-506.

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  Conflict of Interest:
  None declared.

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• Published on: 23 November 2015

  Lowering CVD risk: walk before we run

  • Michael J. LaMonte, Physiologist/Epidemiologist
  • Other Contributors:
    • Ted D. Adams, Frank G. Yanowitz

  Dear Editor

  Yu et al.[1] presented the association between self- reported leisure-time physical activity (LTPA) and 10-year cardiovascular (CVD) mortality among 1975 men who were 49-64 years and free of CVD at baseline. Based on 111 CVD deaths from 20,703 man-years of exposure, and after adjustment for selected confounding effects, the investigators concluded that higher levels of daily energy expenditure in v...

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  Dear Editor

  Yu et al.[1] presented the association between self- reported leisure-time physical activity (LTPA) and 10-year cardiovascular (CVD) mortality among 1975 men who were 49-64 years and free of CVD at baseline. Based on 111 CVD deaths from 20,703 man-years of exposure, and after adjustment for selected confounding effects, the investigators concluded that higher levels of daily energy expenditure in vigorous intensity LTPA were significantly related with reduced risk of CVD death. However, energy expenditure combined from light and moderate intensity activities was not significantly related to CVD mortality.

  The study findings are important as they provide further documentation of the cardioprotective effects of an active lifestyle. However, we are concerned about the conflict between the current study’s conclusion that vigorous physical activity is required to lower cardiovascular risk and the large evidence base supporting cardiovascular risk reduction from regular moderate intensity activity.[2-5] Conclusive evidence for a specific dose-response relationship between physical activity volume or intensity and CVD mortality remains elusive.[6] A major limitation to assessing, interpreting, and comparing dose- response characteristics between physical activity and CVD mortality is considerable inter-study variability in quantifying physical activity as an exposure variable.[6,7]

  We believe measurement issues may underlie the lack of association between moderate intensity activity and CVD mortality reported by Yu et al. First, the authors indicate that a physical activity questionnaire previously validated among middle-aged American men was modified to survey physical activity among the study’s cohort of British men. It is known that responses to physical activity questionnaires vary by age, sex, race-ethnicity, and sociocultural factors.[7] Therefore, it would be useful to know how the questionnaire’s original format was modified and whether these changes altered the validity and reliability characteristics of the physical activity measure, particularly with respect to moderate intensity activities which are more difficult to recall than vigorous intensity activities.[7] Second, the observed association between energy expended in vigorous intensity activity and CVD mortality is based on a relatively small proportion of the sample’s total energy expenditure (see Yu et al, Table 1), which should be taken into account when interpreting the practical implications of these findings. Third, the authors collapsed energy expended in light activity with energy expended in moderate activity without providing a rationale for this aspect of their analysis. The more appropriate examination of the effect of energy expended in different intensities of leisure physical activity on CVD mortality would come from separate models of the association between intensity-specific energy expenditure and CVD mortality.[8] Furthermore, current public health recommendations indicate the cardioprotective effects of physical activity are derived mostly from energy expended in moderate-to-vigorous intensity activities with an absence of evidence supporting such benefits from light intensity activities.[2-5] It, therefore, seems the author’s analytic model combining light and moderate intensity activity is contrary to existing evidence and should be justified in their text. We believe this approach would suppress the true effect of moderate intensity energy expenditure on CVD mortality, and bias the strength of association for the model of “light-moderate intensity” activity and CVD mortality towards the null. We are concerned that misinterpretation of this finding will result in confusion among practitioners as to the appropriate type of activity to recommend to sedentary or irregularly active individuals. More importantly, this might dissuade such individuals from adopting a more active lifestyle of moderate intensity activities through which substantial health benefits and cardiovascular risk reduction can be obtained.[2,6]

  References

  (1) Yu S, Yarnell JWG, Sweetnam PM, and Murray L. What level of physical activity protects against premature cardiovascular death? The Caerphilly study. Heart 2003;89:502-506.

  (2) Fletcher GF, Blair SN, Blumenthal J. et al. Statement on exercise: benefits and recommendations for physical activity programs for all Americans. Circulation 1992;86:340-344.

  (3) US Department of Health and Human Services. Physical Activity and Health: A Report of the Surgeon General. Atlanta, GA: USDHHS, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, 1996.

  (4) Pate RR, Pratt M, Blair SN, et al. Physical activity and public health: a recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. JAMA 1995;273:402-407.

  (5) NIH Consensus Development Panel on Physical Activity and Cardiovascular Health. Physical activity and cardiovascular health. JAMA 1996;276:241-246.

  (6) Kohl HW. Physical activity and cardiovascular disease: evidence for a dose-response. Medicine and Science in Sports and Exercise 2001;33(6 Suppl):S472-S483.

  (7) LaMonte MJ, and Ainsworth BE. Quantifying energy expenditure and physical activity in the context of dose response. Medicine and Science in Sports and Exercise 2001;33(6 Suppl):S370-S378.

  (8) Lee IM and Paffenbarger RS. Associations of light, moderate and vigorous intensity physical activity with longevity. The Harvard Alumni Health Study. American Journal of Epidemiology 2000;151:293-299.

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  Conflict of Interest:
  None declared.

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