Exercise as it relates to Disease/Tortise vs hare....does walking faster have better health outcomes?

This wiki critiques the article: Stamatakis, E., Kelly, P., Strain, T., Murtagh, E.M., Ding, D., and Murphy, M.H. (2018). Self-rated walking pace and all-cause, cardiovascular disease and cancer mortality: individual participant pooled analysis of 50225 walkers form 11 population British cohorts. British Journal of Sports Medicine, 52, 761-768.

What is the background to this research?
The health benefits of walking are well established in the literature. Public health campaigns, such as those run by the Heart Foundation and the government guidelines on physical activity often focus on the duration and frequency of walking to obtain health benefits. Research has shown that meeting the physical activity guidelines through walking resulted in a reduction of 11% in risk for all-cause mortality and a higher volume resulted in a bigger reduction of risk for cardiovascular disease mortality when compared with a lower volume or walking. The benefits regarding cancer mortality are less certain.

It is believed that a greater intensity from walking at a faster pace will elicit a greater physiological response and greater or perhaps additional health benefits. Prior to this study, little research has been done on the health effects of walking pace. Most of the research that was done did not take into account that the increased pace usually resulted in a higher overall level of physical activity. This study aimed to look at the relationship of walking pace with mortality (all-cause, cardiovascular disease and cancer) independently of total physical activity.

Where is the research from?
This article was a collaboration between researchers in Australia (from the University of Sydney) and researchers in the UK (from the Universities of Edinburgh, Cambridge, Limerick and Ulster). Between them they have published hundreds of papers in the fields of exercise science, physical activity and sedentary behaviour, obesity, the benefits of waling and active transport.

The lead author, Emmanuel Stamatakis is considered an expert in the field of epidemiological research in health related behaviours and their impact on cardiometabolic and mental health (among others). He is currently the Professor of Physical Activity, Lifestyle, and Population Health at the Charles Perkins Centre, Sydney Medical School, School of Public Health at the University of Sydney and is the number one most published author in the field of sedentary behaviour epidemiology.

There did not appear to be any conflicts of interest or competing interest of the authors. The study was funded by the National Institute for Health Research (UK) and the National Health and Medical Research Council (Australia).

What kind of research is this?
This was an epidemiological study looking at the over 50000 respondents from British surveys including the Health Survey for England and the Scottish Health Survey. The pooled data from these studies was linked with the mortality data which was coded using a combination of both ICD-9 and ICD-10 classifications. It adhered to the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) standards for observational studies.

Cause and effect cannot be determined from studies such as these, however where strong correlations are found, they can be used to inform further research to try and help determine causation.

What did the research involve?
This prospective study pooled data from 11 population household-based surveys conducted between 1994 and 2008 in England and Scotland. Data from 50 225 people who participated in the surveys was used as they met the criteria of having walked at least once in the previous 4 weeks, were aged over 30 and did not have a diagnosed cardiovascular disease, cancer or a history of stroke or angina. The data from the surveys was matched with the NHS Central Mortality Register and was analyzed looking for associations between different walking paces (self-reported) and cancer, cardiovascular disease and all-cause mortality.

The different surveys (and different iterations of the surveys) used different definitions for an ‘occasion of walking’. These varied between 10 minutes, at least 15 minutes or at least 30 minutes. Participants were asked the average time they spent walking, the number of days walked during the previous 4 weeks and their walking pace – slow, average, fairly brisk or fast (which was defined as at least 4 miles per hour). This data was used to generate an average time spent walking per week and then when combined with the pace a MET-hours/week was calculated and used in the analysis.

A limitation of this study is the self-reported nature in the way the data was collected. Due to the nature of self-report walking pace and volume may have been subject to errors and biases.

What were the basic results?
When comparing walking pace with all-cause mortality (ACM), cancer mortality and cardiovascular disease (CVD) mortality and adjusting for total physical activity, total walking volume and MET hours per week, the results showed:
 * ACM had a 20% risk reduction for those who walked at an average pace when compared to the slow pace, with a 24% risk reduction for those in the brisk/fast pace group.
 * CVD mortality had a 24% risk reduction for those walking at average pace and a 21% risk reduction for those in the brisk/fast pace group when compared with the slow group.
 * There were no significant results for comparing cancer mortality with various walking paces

Risk reduction all ages
(compared with slow walking pace)

The lack of and significant results comparing walking pace and cancer mortality is consistent with recent analysis of UK Biobank observational study.

These results are even more pronounced when looking at only the over 50’s:

Risk reduction Over 50's
(compared with slow walking pace)

What conclusions can we take from this research?
This research shows that increasing walking pace without increasing duration can increase the risk reduction for all-cause mortality and cardiovascular disease mortality. Those aged over 50 can have an increased risk reduction especially when a brisk or fast pace is adopted.

The conclusion can be made that in this instance the hare is the winner, with larger risk reductions for ACM and CVD mortality for those who walk at an average or brisk/fast pace when compared to the slower paced walkers.

Practical advice
These findings are of particular importance because often people have the excuse that they do not have time to do any more (or any) exercise. These results can help inform future public health campaigns regarding the intensity of walking along side the duration recommendations. In situations where the duration and volume of walking cannot be increased, the intensity can be increased with additional health benefits possible without any more time commitment. Based on the results, this is especially of use to those aged over 50.

Further information/resources
This research was published in May 2018, so there has not been time for much further research to have been published to further support these claims.

There are however resources available for those wanting to join a walking group: Heart Foundation http://walking.heartfoundation.org.au/benefits-of-walking/walking-tips/ and in their recommendations they do specify moderate and vigorous intensity to comply with the National Physical Activity and Sedentary Behaviour Guidelines.

There is also an interesting Australian study from 2014, whilst not looking at mortality looks at the relationship between moderate and vigorous physical activity and changes in weight gain and physical function.