The steps in reserve : An unexploited way to make our children more active during their daily routine

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1 1 The steps in reserve : An unexploited way to make our children more active during their daily routine Catherine Morency* and Marie Demers *Department of Civil, Geological and Mining Engineering, Ecole Polytechnique of Montreal, CIRRELT Montreal, and Centre de recherche clinique, CHUS, University of Sherbrooke, Sherbrooke, QC, Canada ABSTRACT Background: This study examines how active transportation could help increase the daily physical activity volume of school aged children. Methods: Using data from the 2003 Origin Destination survey carried out among 5% of the 3.5 million residents of the Greater Montreal Area, we determined the proportion of short motorised trips made daily by children 5 to 14 years old (16,837 children sampled) and estimated the number of steps these trips would account for if they were traveled by foot, taking into account variables such as age, sex and height of children. Modal choice and trip purpose were also examined. Results: In 2003, 31.2% of the daily trips made by children aged 5 to 14 in the Greater Montreal Area (GMA) were 1 km or less (0.6 mile). Of these, 33.0% were motorised trips. Overall, 13.1% of the children in the area had "steps in reserve", an average of 2,238 steps per child per day. If they were performed, these steps would account for 16.6% of the daily recommended volume of physical activity for children. Conclusion: Replacing short motorised trips with walking would increase the physical activity level of children and contribute to meet the recommended guidelines.

2 2 KEY MESSAGES Most children are not enough physically active to meet the recommendations Integrating physical activity in their daily routine could benefit those children who do not get involved in sports This study found that walking to school instead of traveling using a motorized mode of transportation could help increase the physical activity level of children A significant portion of children live at a walkable distance from school but are driven by car

3 3 INTRODUCTION Childhood obesity is booming in most industrialized countries (IOTF, 2005) and Canada is no exception: in 2004, 26% of Canadian children and adolescents aged 2 to 17 were overweight or obese (Shields, 2005). The prevalence of obesity among the 7 to 13 years old has tripled in Canada from 1981 to 1996 (Tremblay et al., 2000). Social and environmental changes taking place during the last decades have led to poor eating habits combined with increased physical inactivity (Demers, 2006), both factors contributing to the obesity epidemic (Janssen et al., 2004, Katzmarzyk and Ardera, 2004, Tremblay and Willms, 2003). Less than half of Canadian children and youth are now physically active enough to meet the guidelines for healthy growth and development (Active Healthy Kids Canada, 2006), which recommend 60 minutes or more of moderate to vigorous physical activity every day (Strong et al., 2005). More than half Canadian children are watching two to four hours of television daily, and approximately a third are spending two hours or more on leisure related computer use (Active Healthy Kids Canada, 2006). Opportunity for physical activity at school does not seem adequate either: according to a recent Montreal based study of elementary schools, the median was only 29 minutes per day (Barnett et al., 2006). Cycling and walking to school have also declined tremendously, and wherever they go, children are usually transported by car, which also increases their dependence towards adults (Strong et al., 2005, Barnett et al., 2006, McDonald, 2007). Nevertheless, experts say that active transportation has been largely ignored as a possible source of physical activity among children (Tudor Locke et al., 2001). There is no unique solution for increasing the physical activity level of children, but a closer look at how

4 4 they are moving around could help design new avenues in the promotion of active transportation. The aim of this study is to examine the modal choices for the daily trips taken by children in the Greater Montreal Area, and to estimate to what extent short motorised trips could rather be made on foot, thus helping them to reach a higher level of physical activity. Converting short motorised trips into walking steps has recently allowed estimating how many residents of the Greater Montreal Area have Steps in Reserve and how many daily steps they have which constitutes an original way to look at active transportation in a promotion perspective (Morency et al., 2007). In this previous publication, we showed that children aged 5 to 14 were more numerous to have steps in reserve and had more steps in reserve compared to other segments of the population for trips less than 1.6 km. Since this distance might be considered too long for young children under certain circumstances, it was decided to investigate the situation among children when a shorter distance was considered. The technique allowed estimating how many steps could be added to the daily routine of children if their short motorised trips were replaced by walking. METHOD DATABASE, STUDY AREA AND POPULATION The Greater Montreal Area (GMA) is the largest urban area in the province of Quebec, covering 5,500 square km and including 3.5 million residents, i.e. nearly half of the province population. A large scale Origin Destination (OD) travel survey is conducted in the area approximately every five years since The latest survey, conducted in the fall of 2003, allowed collecting detailed information regarding the daily travel behaviors of approximately 5% of the people

5 5 residing in the area. The survey provides information on travel behaviors during a typical weekday and on the socio demographic characteristics of travelers. In 2003, around 70,000 households were interviewed by phone; data were gathered on more than 360,000 trips made by some 165,000 people, including more than 17,000 children aged 5 to 14. The information is available for 16,837 children who made 41,104 trips. Since the sample survey is weighted in order to represent the whole population, this sample represents the daily travel behaviors of nearly 450,000 children residing in the area. Travel distance estimation Every individual trip was precisely detailed in space and time. Contrary to the often used zoning systems for the coding of trip ends, origin and destination points were geocoded at the x y coordinate using various types of identifiers such as trip generator, address or intersection. Hence, the estimation of travel distances, using a trip assignment model, is quite straightforward and precise. Travel distances of short motorised trips were obtained using a trip assignment model that assigned every individual trip on a detailed road network rather than as the crow flies. Precise x y coordinates of the origin and destination points were inputted in the assignment model which determined the shortest path on the available network. Since the idea was to convert motorised trips into non motorised ones, distance was used as generalized cost instead of travel time. It seemed like the most relevant hypothesis because the focus was on short trips and the purpose was to estimate the walking distance between two closest points. This technique has been used previously for all population segments (Morency et al., 2007). The distribution of children s travel distances for walking trips shows that 76.3% were 1 km or less.

6 6 This proportion declined with age but the average distance increased as children grow older (Table 1). Table 1. Proportion of short walking trips (1 km or less) and average distance by age group It was then decided to use 1 km as a cut off point as a suitable walking distance for the conversion of motorised trips into potential walking steps (called "steps in reserve"). In order to do so, a few methods and hypotheses needed to be used. The first tool required is a trip assignment model to precisely estimate the length of each trip on the transportation networks. A conversion process relying on adapted stride lengths for age groups by gender was then applied to every single trip to estimate the number of steps that would be made if there were a switch in mode to walking. We hypothesized that all short motorised trips could be traveled by foot if the appropriate measures were implemented. A more realistic estimation would eventually require the precise examination of the spatio temporal circumstances under which each trip is made, as well as all the other constraints such as tight scheduling, bags to carry, safety and so on. Again, even with these constraints, some measures could be implemented to facilitate the transfer. Distance to steps conversion Very few attempts have been made to determine the number of steps required to cover a specific distance. Among adults, there is an agreement that one mile accounts for about 2,000 steps (1,243 steps per kilometer), which means an average stride length of 2.5 feet (Fletcher, 2005, The Walking Site). Due to their smaller size, children have a shorter stride length. Average stride lengths were estimated under the hypothesis that they correspond to approximately 42% of a person height (UCLA Recreation Department, 2008). Hence, growth charts for boys and girls

7 7 were used to determine average heights for two year age groups by gender. The resulting stride lengths and steps per km used in the estimation of steps in reserve are presented in Table 2. Table 2. Average stride lengths for children per age and sex RESULTS Traveling habits of children Details on the mode choice among children are given in Figure 1 where the proportion of daily trips made using six main transportation modes are illustrated by age group whatever the distance traveled. It clearly shows that for young children, traveling highly relies on car and thereby on adults with almost half the trips being made as car passenger. Walking was more common among the 9 10 years old and reached a lower level among older children (13 14 y.o.); for the latter, school bus was the most important transportation mode. Figure 1. Mode choice of children for their daily trips according to age group (2003 OD Survey) An important portion of daily trips made by children were relatively short. More than half the trips made on a daily basis by the children living in the Greater Montreal Area were 2 km or less in 2003 and 31.2% of all daily trips made by children were 1 km or less, one third involving a motorised mode (Figure 2). Whatever the distance considered, walking and cycling never accounted for more than 29% of daily trips. The proportion of short motorised trips varied from 46.3% for youngest children to 20.1% in the oldest group. Most of these short motorised trips (77.6%) were made as car passengers (Table 3). As shown in Table 3, cycling accounted for only a small portion of short daily trips. Figure 2. Cumulative distribution of traveled distances by mode (2003 OD Survey)

8 8 Table 3. Modal split for short trips according to age group Steps in reserve among children All short motorised trips 1 km or less were then converted into steps using the average stride lengths reported in the method section and the specific distance computed for each of these short trips. Overall, 13.1% of the children had steps in reserve i.e. they made at least a part of their daily short trips using a motorised mode rather than walk (Table 4) and could benefit from a potential conversion from a motorised mode of transportation to walking. Between 5 and 8 years of age, the proportion of children with steps in reserve reached approximately 20%. The average number of daily steps in reserve was 2,238 for the whole sample and reached a maximum of 2,510 steps among the 5 to 6 years old, declining to 1,612 steps for the 13 to 14 years old. The lower amount of steps in reserve among the older groups was partly attributable to a longer stride length but also to a lower overall distance covered by short motorised trips. A similar proportion of boys and girls had steps in reserve, but boys had slightly more steps in reserve than girls, overall and for all age group except the oldest. Table 4. Children with steps in reserve per age and sex Three quarters of the steps in reserve stemmed from short daily trips as car passenger; the proportion was slightly higher among the younger age groups (Figure 3). School bus trips also accounted for a significant portion of steps in reserve. It is noteworthy that 20% of short daily trips were made by school bus instead of walking on such a short distance even among the oldest groups. Moreover, some members of the oldest group used transit for trips shorter than one km, as revealed by their steps in reserve resulting from this mode of transportation. When

9 9 the destination was examined, it was found that most steps in reserve were related to daily trips to school (Figure 4). Among the years old, leisure and shopping activities accounted for at least 25% of short daily trips. Figure 3. Distribution of steps in reserve according to mode choice per age group Figure 4. Distribution of steps in reserve according to trip purpose per age group (excluding journey home) DISCUSSION Even when short distances are involved, traveling to school in the Greater Montreal Area relies often on a motorised mode of transportation. This situation is not unique to cold countries but characterizes also southern countries such as Australia (Wen et al., 2007). The conversion of short daily motorised trips into walking steps could contribute to increase the physical activity volume for 13.1% of the children in the Greater Montreal Area. Considering the number of daily steps recommended for youth physical activity (12,000 steps for girls and 15,000 steps for boys aged 6 to 12) (Tudor Locke et al., 2004), the average number of steps in reserve estimated in this study would represent approximately 16.6% of the daily recommended volume for those children who have steps in reserve, most of it stemming from commuting to school. A study carried out in the US found that regular active commuters to elementary school accumulated 3% more minutes of moderate to vigorous physical activity during weekdays compared to other groups, which translated into 24 additional minutes of physical activity per day among fifth graders (Sirard et al., 2005). Studies are still inconclusive about the influence of active commuting to school on BMI (Heelan et al., 2005, Landsberg et al., 2007, Rosenberg et al., 2006) but walking to school was associated with higher levels of overall physical activity

10 10 among primary school aged children (Cooper et al., 2005, Cooper et al, 2003) and therefore may contribute to the attainment of physical activity recommendations (Heelan et al., 2005). Nevertheless, the caloric energy expended while walking is higher than when traveling by car (Ainsworth, 2006). Measuring children s physical activity with the help of sensors, British researchers found that on average, children aged 10 to 13 gained 9% of their daily physical activity traveling to and from school (Mackett et al., 2004); they even found that children spend more calories commuting to school daily than they would from two hours of physical education per week (Mackett et al., 2003), which suggests the high potential of active transportation as a source of physical activity at the population level if appropriate policies were implemented. One might argue that walking to school even for short distances may be too dangerous, due to poor road design, inadequate pedestrian infrastructures and heavy traffic, but these factors can be modified to encourage walking among children, particularly in a context of increasing childhood obesity and physical inactivity. Some programs like the Walking Bus and Safe Routes to School have already been implemented in many countries to encourage active commuting to school among children. Relevant policies for active transportation to and from school have recently been identified and include measures on school speed zone, drop off, no transport zones, school siting, school start/dismissal time, school choice, and factors related to the built environment such as the presence of sidewalks, crosswalks and crossing guards (Eyler et al. (2007). According to Tudor Locke et al (2001), active commuting to school has been largely ignored in surveys of physical activity among children and thereby represents a missed opportunity for children s health related physical activity in motorized societies (Tudor Locke et al., 2002).

11 11 The 1 km cut off point adopted in this study represents a rather short walking distance for older children, especially for those attending high school (children aged between 12 and 14, which account for 32% of the sample), suggesting that longer motorised trips (all trips less than 1.6 km for instance) could be converted into steps in reserve for this part of the sample. This would increase the proportion of children with steps in reserve. Thus, our estimate of 13.1% is probably an underestimation of what could be expected from the conversion of short motorised trips into walking steps. This study does not rely on step counts from pedometers but is based on the conversion of traveling distances into steps which lead to estimations rather than real counts, so the results should be interpreted cautiously. Inferences have to be made about the average stride length per age group in order to determine the number of steps required to travel one km or less. This approach does not provide an accurate measure of steps for a specific child or a small sample of children but should be more valuable at the population level. Considering the sample size of the study (i.e. nearly 17,000 children), the use of pedometers would be unrealistic; in this situation, estimates based on exact traveling distances provide a valuable tool for examining at the population level how walking can be integrated in children s daily routine. Another limitation is the absence of data on the environmental constraints for walking among children who used a motorised mode of travel on a 1 km distance. Since the precise x y coordinates for each trip are known, it would be possible to address this issue in a further study and examine how environmental characteristics encourage or limit walking. For example, it has been shown that children from grade 6 to 8 were more likely to walk to school when the intersection density was high and fewer dead ends present (Schlossberg et al., 2006). But here,

12 12 the purpose was to illustrate how this new technique could be used to measure the steps in reserve among children at the population level and see how active transportation could contribute to increase the physical activity level of children, considering the fact that a large portion of their daily trips are rather short. Other benefits would be a lesser dependence of children towards adults for moving around (Merom et al., 2006) and a reduction of traffic induced around school by parents driving their children, as well as of vehicle emissions from these trips (Ewing et al., 2005).

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