Wednesday, July 17, 2013

Youth Sports, Physical Activity and Energy Expenditure, Professor Donald Siegel

Over the years various organizations have called for children to get sufficient physical activity for the purpose of promoting lifelong health, and to minimize the potential for succumbing to a variety of morbidities associated with lifestyle choices such as obesity, Type II diabetes, heart disease, and some forms of cancer.[1] Currently, the common consensus is that children should get a minimum of 60 minutes of moderate to vigorous activity on most days of the week.[2] While this target may seem fairly modest, research shows that 61.5% of 9-13 year olds do not engage in physical activity during their non-school hours[3] and that underserved youth even fare more poorly.[4] An approach that is being embraced by experts in exercise science to increase physical activity levels in youth is to identify various periods in a child’s day and during each such epoch promote enhanced activity levels. For example, children are encouraged to be active prior to the start of school, be offered physical education and recess during the school day, and then be encouraged to participate in various afterschool sports programs. As an aggregate, experts believe that such multifaceted involvement will summate and result in more youth meeting the 60 minutes goal.

Clearly, physical activity is a core element of sports based youth development programs. Yet, sport is a rather amorphous concept, and depending upon activity type, duration, intensity and frequency, a wide range of experiences can exist among youth engaged in a sport’s program. Whether or not children realize the 60 minutes of moderate-vigorous activity goal, despite participating in a sports program is equivocal. This is not to argue that satisfying physical activity needs is the only or most compelling reason for a youth to participate in a sport based youth development program, but our research suggests that with some “tweaking” most such programs can be enhanced to produce greater energy expenditures in the youth that they serve. Everything else being equal, we believe that just as staff wish to enhance the acquisition of their youths developmental assets, and academic achievement, they should also be deliberate about promoting optimal levels of physical activity in the sports that they teach. 

[2] National Guidelines for Physical Activity from the National Association for Sport and Physical Education:

Connection Among Activity Data, Sports, and Coaching

While many studies have assessed the energy expenditures for adults engaged in various sports, relatively few have been done using children as subjects. The most recent study targeted at youth is a compendium of results, using mostly energy expenditure estimates derived from adults.[5], As well, a summary table produced by this study, which associates various activities with caloric expenditures, although helpful, is also somewhat difficult to interpret for sport based youth development practitioners who are interested in bridging the gap between theory and practice.[6] A previous study also provides general “ballpark” estimates of energy expenditure of children, grades 6 -8, engaged in sports, which also suffers from using estimates and subject recall of activity type and dosage, for youth participating in basketball, skiing, soccer, wrestling, football, cheerleading, volleyball, swimming, and tennis. Researchers concluded that, on average, boys and girls, expended 20.4% and 16.3% respectively, of their daily caloric expenditure in sports. From these data, they also concluded that 55% of these calories were burned in moderate-vigorous activity for boys, and 64.6% for girls.[7] While such studies provide rough estimates for energy expenditures in sports activities, in general, they provide little guidance for program staff orchestrating sports with a particular group of youth, for a limited amount of time, in a specific setting. Given that different sports normally lend themselves to lesser or larger amounts of activity, as does a participant’s maturity and skill level, what occurs in real time in a particular sport session is highly dependent on a coach’s goals and his pedagogical capabilities. For example, while descriptive studies of sport and energy expenditure may produce general guidelines on the relative merits of basketball, soccer or tennis, they tell us very little about how a particular youth, in a particular program, orchestrated by a particular coach expends energy during the time he or she is engaged in such a session. Over the years we have observed practices in these sports, and others, in which all youth were very active for a large percentage of the time they were there, while in other practices, in the same sports, we have seen youth being sedentary or only modestly engaged for the duration. As we surmise, what transpires during a practice or game is not only dependent on the sport, but also on the goals and expertise of those leading activities.

As a result of these observations, we have run a series of small studies during the past three years to examine the amount of activity our 3rd – 5th graders are actually getting as Project Coach participants. In these studies we attached accelerometers to youth while they engaged in randomly selected volleyball and basketball sessions. Accelerometers are devices that assess movement in three dimensions, and in contrast to the indirect measures used in the aforementioned studies, they come closer to providing data which more closely connects what a child is actually doing in real-time with energy expenditure measures. Based on the activity counts that are provided, algorithms can then convert raw data to more useable measures such as calories expended, percent of time in sedentary/moderate/vigorous activity (METS/unit of time), and steps taken. While accelerometers can really only provide estimates of these measures, they are easy to use, are relatively unobtrusive, and have been shown to have relatively high correlations with more direct measurements such as oxygen consumption[8]. As well, they can provide sport based youth development staff with critical information about how much activity kids in their program are really getting.

[5] Ridley, K., Ainsworth, B. E., and Olds, T. S. (2008). Development of a compendium of energy expenditures for youth. International Journal of Behavioral Nutrition and Physical Activity, 5: 45.
[6] For a table of activities and their metabolic equivalents (METS) see:
[7] Katzmarzyk, P. T. and Malina, R. M. (1998). Contribution of organized sports participation to estimated daily energy expenditure in youth. Pediatric Exercise Science, 10, 378-386.
[8] de Vries, S. I., van Hirtum, Helmi W. J. E. M., Bakker, I., Hopman-Rock, M., Hirasing, R. A., & van Mechelen, W. (2009). Validity and reproducibility of motion sensors in youth: A systematic update. Medicine & Science in Sports & Exercise, 41(4), 818-827

How Have Accelerometer Data Affected our Practice?  
In our first study we attempted to find out whether 3-5th graders, who were involved with the Project Coach basketball program, were actually getting more activity than they would normally get had they not been in the program and left to do whatever they typically do after school. Consequently, we had 19 girls and boys wear accelerometers on a day when they had Project Coach and a day when they did not.  The participants wore the devices from 8:00 a.m. to 5:30 p.m, basically from the start of school to the end of their after school hours. The data that we were particularly concerned with was the hour from 4:30 to 5:30, which is the time of the Project Coach sports session. However, having the data for the entire day was crucial because it allowed us to compute the percentages of physical activity that a child got throughout the day. That is, we were able to determine the level of activity the child was getting at each hour of the day. The measurements collected were then converted into percentages. Our hope was that Project Coach was contributing to a large percentage of the child’s daily physical activity. In Chart 1, we can see the percentages of calories burned at each hour of the day. We found that Project Coach participants burned approximately 28% of their calories during the sports session, which is the largest percentage represented in Chart 1. We also found that in comparison to the non-Project Coach day our participants were burning 10% more calories when they were in the Project Coach sports sessions.

Chart 1

Chart 2, portrays the average number of steps taken at each hour of the measurement period. According to our data, the average steps taken during the Project Coach sports hour was 2,000. On the non-Project Coach day, our participants took 500 steps in the hour from 4:30 to 5:30. We also noticed that there was an increase in steps taken during the 3:30 to 4:30 hour. Our hypothesis for this unexpected spike in steps is that the group of participants walked to the playing venue which was more distant than if they had simply walked home from their school to the gym at the Gerena school.

Chart 2

In Chart 3, the MET (Metabolic Equivalence) levels of nine of our participants are represented. Simply put, METs measure how hard your body is working. The harder your body works, the more oxygen it burns to release the energy it needs to perform the activity. At complete rest, on average, your MET level would be 1. We found during the Project Coach hour from 4:30 to 5:30 that 42% of the time our participants were at a level of 3 – 6 METs, which is considered moderate activity. For 12% of that hour, our participants were at a level of 6 – 9 METs, which is considered to be vigorous activity. On average, these 9 participants were at a level of 3.8 METs.

Chart 3 

Theory to Practice
While these data clearly support the added value of participation in Project Coach to enhancing a child’s daily physical activity level, we have also learned that a fairly high percentage of the time (approximately 45%) that a child is at Project Coach he/she is engaged in sedentary or light activity. Subsequent studies that we have done with our volleyball and basketball programs have corroborated these patterns. The obvious question for us is how to shift the distribution in Chart 3 so that the bars on the right side are incremented, while those on the left side are reduced?

Initially, our staff met, processed what we were finding with these energy expenditure data, and planned various interventions to increment activity levels. For instance, when we went back and looked at the actual activity that youth were getting in volleyball we found that because of low levels of skill, there was minimal ongoing action, a great deal of time spent retrieving balls that had gone astray, and, consequently, too much standing around. As a response, we purchased beach balls that were larger, softer, and floated back and forth more slowly so that children had more time to position themselves and successfully keep rallies going. We also reconfigured some game-like activities so that children had to quickly move from one side of the net to the other as they struck balls. Another variation that we tried entailed introducing random exercise breaks during which coaches blew their whistles and then asked children to do jumping jacks, run in place, or do sit-ups. These types of enhanced physical activity offerings also were used in our basketball program during games. Rather than simply having half of a team sit on the bench while the other half played, we asked coaches to engage those on the bench in various sideline drills while they waited for their turns to enter the game.

Having “the data” clearly sensitized us to where we were with regard to maximizing physical activity levels with our players. Coaches became acutely aware that they needed to get and keep their kids moving, and that periodically having players wear accelerators would provide feedback as to whether they were able to do so. Subsequent studies that we have run have produced promising results. Game modifications, and various types of “exercise breaks” within activities have resulted in increasing the overall activity levels of our youth, as well as moving more of them toward moderate and vigorous levels during the course of a session. However, we also realize that we can still do more. Currently, we are working on crafting more activities/games, within the sports that we run, that engage all players on a team simultaneously, and keep them moving as much as possible for the hour that they are with us. We are also working with our coaches to help them to reduce their talking time, and to get their players, as quickly as possible, into planned activities. In contrast to more traditional approaches that promote the notion that youth need to have acquired a higher level of technical/tactical knowledge before playing various games (which also means less physical activity), we believe that coaches can teach the technical and tactical aspects of games by using intermittent feedback to shape the play of their players from the start (i.e., the games approach). So far, we see little downside to this approach as youth seem to be learning as much, and enhancing their levels of physical activity.

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