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.