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.
[2]
National Guidelines for Physical Activity from the National Association for
Sport and Physical Education: http://www.aahperd.org/naspe/standards/nationalGuidelines/PAguidelines.cfm
[4] http://www.womenssportsfoundation.org/home/research/articles-and-reports/mental-and-physical-health/go-out-and-play
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. http://www.ijbnpa.org/content/5/1/45
[6]
For a table of activities and their metabolic equivalents (METS) see: http://www.ijbnpa.org/content/supplementary/1479-5868-5-45-s1.pdf
[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 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.
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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