Today’s guest post comes from my friend, colleague, and former labmate Richard Larouche. You can find out more about Richard at the bottom of this post.
Regular readers of Obesity Panacea will know that today’s children are not active enough. For example, according to the 2007-2009 Canadian Health Measures Survey, only 9% of boys and 4% of girls meet the Canadian physical activity guidelines (Colley et al., 2011, available here). These guidelines recommend that children and youth accumulate at least 60 minutes of daily moderate-to-vigorous physical activity – that is activities that are intense enough to increase one’s heart rate and accelerate breathing.
There are many sources of daily physical activity including organized sports, physical education, active transportation, household tasks, etc. Today, I will focus on active transportation, which is the use of non-motorized means such as walking and cycling to travel to and from places.
Travis and I have recently published a comprehensive review of 68 studies that looked at active transportation to and from school among children and youth (Larouche et al., 2014a, available here). To be eligible for the review, studies needed to examine the relationship between active transportation and one of the 3 following outcomes: 1) physical activity; 2) body composition (i.e., body weight and waist circumference); and 3) cardiovascular fitness.
We found consistent evidence that active transportation was associated with higher physical activity levels, not only during the journey to and from school, but during the whole day as well. Furthermore, the difference in physical activity between children using active vs. motorized travel modes was even greater among those who traveled longer distances.
35% of the studies showed that active travelers had a more favourable body composition. However, over half of the studies found no such differences. In our article, we proposed several potential explanations for these findings. I will briefly mention 3 of these hypotheses:
- Active travelers may compensate for the increased energy expenditure during active transportation by eating more during the rest of the day.
- The energy expenditure of active transportation may simply be insufficient to have a substantial impact on body composition for the typical child who walks or bikes to and from school over a short distance.
- Active transportation tends to be more common among children from low socio-economic status families (e.g., families with lower income and/or parental education level). Previous studies indicate that these children are more likely to be overweight or obese.
Finally, for cardiovascular fitness, our findings differed by travel mode. Indeed, the association between walking to and from school and fitness was inconsistent: some studies showed no differences and others found that walkers were slightly fitter. However, all 5 studies that specifically examined cycling found that cyclists were substantially fitter. This included a 6 year longitudinal study which showed that children who switched from motorized travel to cycling increased their fitness over time.
The Canadian Health Measures Survey
More recently, I performed a series of analyses using data from the 2007-2009 Canadian Health Measures Survey (Larouche et al., 2014b, available here). This survey conducted by Statistics Canada is representative of the overall Canadian population.
In the survey, 1,016 youth aged 12-19 years were questioned on the amount of time that they usually spend walking and cycling while traveling to and from school or work or while doing errands. This provided an opportunity to examine active transportation beyond the school trip and how it relates to physical activity, body composition and cardiovascular disease risk factors.
Both walking and cycling were associated with higher physical activity levels, even after controlling for gender, age, parental education and the complex survey design.
However, the association between walking and health outcomes was not straightforward. Indeed, compared to children who reported walking between 1 and 5 hours per week, those who walked either more or less tended to have a more favourable health profile. The 3 hypotheses that I mentioned previously may potentially explain these rather puzzling findings.
Nonetheless, we know that travel mode choices tend to be very habitual. In other words, once a given mode is used routinely for a given purpose, there is no longer a need for conscious decision-making. Therefore, developing the habit to walk during childhood or adolescence may lead to health benefits later in life. This view is supported by a meta-analysis that noted a lower risk of cardiovascular disease among adults who walked to work (Hamer & Chida, 2008, available here).
Our findings were quite different for cycling. We observed that youth who cycled at least 1 hour per week had greater cardiovascular fitness, lower body mass index, lower waist circumference and lower cholesterol compared to those who did not cycle. This highlights substantial benefits of cycling even in young people.
Together, the findings of the 2 studies that I summarized show that active transportation should be promoted as a strategy to increase physical activity among children and youth. Furthermore, cycling may yield additional health benefits among youth, likely because it is a more physically intense activity.
Colley RC, Garriguet D, Janssen I, Craig CL, Clarke J, Tremblay MS. Physical activity of Canadian children and youth: Accelerometer results from the 2007 to 2009 Canadian Health Measures Survey. Health Reports, 2011;22(1):15-24. Available here.
Hamer M, Chida Y. Active commuting and cardiovascular risk: a meta-analytic review. Preventive Medicine. 2008;46:9-13. Available here.
Larouche R, Faulkner GEJ, Fortier M, Tremblay MS. Relationships among active transportation, physical activity, fitness and cardiovascular disease risk factors in adolescents: the Canadian Health Measures Survey. American Journal of Preventive Medicine, 2014;46(5):507-515. Available here.
Larouche R, Saunders TJ, Faulkner GEJ, Colley RC, Tremblay MS. Associations between active school transport and physical activity, body composition and cardiovascular fitness: a systematic review of 68 studies. Journal of Physical Activity and Health, 2014;11(1):206-227. Available here.
About the author: Richard Larouche is a postdoctoral researcher at the Healthy Active Living and Obesity research group. His research focuses on on the health benefits of active transportation and on the factors that distinguish individuals who engage in active transportation and those who don’t. He blogs about cycling, walking, and other related topics at: http://cyclorevolution.blogspot.ca/.