Exercise as it relates to Disease/The warrior way: weekend exercise helps you live longer

This is a critical appraisal of the journal article "Association of "Weekend Warrior" and Other Leisure Time Physical Activity Patterns With Risks for All-Cause, Cardiovascular Disease, and Cancer Mortality by O’Donovan et al. (2017)

What is the background to this research?
It is well established that exercise is good for health, and reduces the risk of mortality. While the international consensus is that we need at least 150 mins/week of moderate intensity exercise, 75 mins/week of vigorous intensity exercise, or some combination of the two, in order to protect ourselves against diseases such as cardiovascular disease (CVD) and cancer, modern lifestyles and work culture often makes it difficult for people to find the time to exercise during the working week. So what about 'weekend warriors', who can only exercise on the weekend - are they protected against the risk of mortality as much as those who spread their exercise more evenly throughout the week? That's the question that O'Donovan and colleagues sought to explore in this study.

Where is the research from?
The study was published in the JAMA Internal Medicine journal. Lead author Dr Gary O'Donovan was a Senior Research Associate in the School of Sport, Exercise and Health Sciences at Loughborough University. Dr O'Donovan has co-authored 54 original research articles on exercise and population health since 2004, with over 2000 citations. The study received funding and support from the UK National Institute for Health Research, with additional support from the Australian National Health and Medical Research Council. No conflicts of interest were disclosed, and funding sources had no involvement in the design or execution of the study.

What kind of research was this?
This retrospective cohort study involved combining and analysing the results from 11 National health surveys from the UK. Cohort studies involve selection of a group of people who do not have a certain condition of interest, and assessing variables which may be related to the that condition. The cohort is observed for a period of time, to see how many develop the condition and examine associations with the variables. Retrospective studies analyse data which has already been collected. This is faster and easier than a prospective study, and inherently free of bias as the original studies weren't intended to address the current purpose; however any study design issues can't be corrected.

What did the research involve?
The Health Survey for England (HSE) and the Scottish Health Survey (SHS) are annual household population health surveys, undertaken by trained interviewers, which collect data on various health, socioeconomic and lifestyle parameters to inform public health policy. Respondents are selected to reflect a representative sample of the population. Data from 63,591 (29,181 male, 34,410 female) respondents to 11 HSE and SHS surveys conducted between 1994 and 2012 were included in this study. Respondents under 40, and/or with CVD or cancer at baseline were excluded. Self-reported physical activity data was examined, with responses filtered into four categories:


 * Inactive (no physical activity reported)
 * Insufficiently Active (reporting less than the recommended weekly physical activity )
 * Weekend Warrior (reporting at least the recommended weekly physical activity in 1-2 sessions per week)
 * Regularly Active (reporting at least the recommended weekly physical activity in >3 sessions per week)

National Health Service data was used to identify survey respondents who have died since the survey and the cause of death. All-cause, CVD and cancer mortality among study participants were recorded in 2016. Those who died within 24 months of the survey were excluded.

A statistical model was used to generate mortality hazard ratios (HR), which compare the risk of dying for people in each Active category against the risk of dying for those in the Inactive category. A HR <1 represents a reduced risk, while a HR >1 represents an increased risk. HRs were calculated for all-cause, CVD and cancer mortality. Data was adjusted for age, sex, illness, smoking status and occupation, to control for factors which might influence the results.

What were the basic results?
A total of 8,802 respondents died from all causes, including 2,780 from CVD and 2,526 from cancer. Respondents in all three Active categories had HRs <1 for mortality from all causes, CVD and cancer.

HRs were similar between women and men. The ratio of vigorous to total exercise time was higher in the Weekend Warriors than in the other Active categories, in both relative and absolute terms.

What conclusions can we take from this research?
Weekend Warriors saw a significant reduction in their risk of death from all causes, including CVD and cancer, similar in magnitude to the other Active groups.

Weekend Warriors performed more exercise at vigorous intensity than the other categories. While vigorous intensity exercise is known to have different benefits to moderate intensity exercise, it is unclear what role exercise intensity played in the magnitude of risk reductions seen in the Weekend Warriors, nor whether Weekend Warrior 'types' are inherently more likely to 'go hard' to make the most of their limited exercise window. This highlights a potential area for more research on optimal exercise prescriptions.

The study does have some limitations which limit the applicability of the results. The study is observational, and thus can't prove causation or 'explain' its findings. Participants were sourced entirely from within the UK, and over 90% of participants were white. The study also relied on self-reported data, which can be susceptible to error. Occupational activity was also not taken into account, and indeed a greater proportion of Inactive participants reported having a manual job. Any influence of this is unclear.

Despite these limitations, a key advantage of this study over previous studies on this topic is the larger cohort size and the inclusion of male and female participants, providing greater statistical power to detect real effects. The study results thus present a strong - albeit correlative - case for engaging in weekend exercise, if that's all you have time for.

Practical advice

 * Meeting the physical activity recommendations is protective against all cause mortality, CVD and cancer.
 * If you don't have time for exercise during the week, completing the recommended amount of exercise in 1-2 sessions on the weekend is still effective.
 * If you can't meet the recommendations, even small amounts of exercise are better than nothing!

Further information/resources
For further information on physical activity for health, visit these websites:


 * WHO physical activity recommendations
 * Find you 30
 * Heart Foundation
 * Cancer Council Australia