Short- and long-term effects of a multi-component physical activity intervention in primary school

There is compelling evidence that physical activity has numerous health benefits
during childhood and adolescence. Insufficient levels of physical activity on the other hand
can consequently affect cardiovascular and bone health, which may result in severe chronic
diseases later in life. Cardiovascular disease and osteoporosis are two of the major chronic
diseases affecting a large proportion of the adult population. Both diseases have their origins
in childhood and it has been shown that for both, physical activity plays an important role in
their prevention. The number of children not being sufficiently active has reached an
alarming level and threatens to impose major health burdens worldwide. Thus, developing
effective strategies to enhance children’s physical activity levels is of paramount interest for
public health. School provides an optimal setting for physical activity promotion, since all
children spend a large portion of their time there. This dissertation discusses a school-based
randomized controlled trial aimed at increasing children’s physical activity levels and
consequently their cardiovascular and bone health.
The „Kinder- und Jugendsportstudie“ (KISS) is a school-based physical activity
intervention lasting one school year. Of all primary school classes in the cantons of Aargau
and Baselland comprising about 10% of the Swiss population, 28 first and fifth grade classes
were randomly selected and allocated into an intervention (16 classes; n=297 children) and a
control (12 classes, n=205 children) group. The mandatory and stringent multi-component
intervention program consisted of daily physical education lessons, daily short activity breaks
during academic lessons, and physical activity homework. Children in the control group had
the compulsory three physical educations per week.
The aim of this dissertation was to assess the effectiveness of KISS on cardiovascular
risk and bone health and to explore whether the program was sufficiently effective in order
to maintain health benefits over the following three years. In addition, this dissertation will
provide a systematic update of existing school-based intervention studies aiming at
increasing children’s physical activity and a quantification of physical education-related
physical activity.
There is strong evidence that school provides a promising setting for physical activity
promotion. All school-based intervention studies done in recent years showed positive effects
in at least one domain of physical activity. The most successful interventions had the design
of a randomized controlled trial, were done over one school year using a multi-component
approach integrated into the school curriculum, taught by physical education experts and
involving family members. A common intervention strategy was to increase quantity and/or
quality of physical education lessons. The particular role of physical education and its
contribution to overall physical activity was the center of attention in the second publication
of this dissertation. Even if children’s physical activity levels during physical education are
relatively low, physical education contributes substantially to overall physical activity.
Due to its nature of being a randomized controlled trial in children with a stringent
physical activity program in and outside physical education over one school year and with
the inclusion of physical education experts, KISS had excellent pre-conditions for being an
effective program. Indeed, the results after nine month of intervention are promising.
Compared to controls, children of the intervention group showed 14% reduced
cardiovascular risk score, 5% reduced body mass index and skinfold thickness, 6% improved
aerobic fitness, 18% higher physical activity levels, and 5-8% higher bone mineral content
and bone mineral density. Three years after cessation of the program, intervention children
still showed higher aerobic fitness and bone mineral content levels at weight-bearing sites of
the skeleton compared to the control group. All other beneficial effects have disappeared.
Even if short-term effects of the intervention are promising, the major key from a
public health perspective is whether the effects of the prevention done during childhood will
persist into late adolescence and adulthood. Although the maintained effects on aerobic
fitness and bone health have considerable impact on public health, most of the beneficial
health effects were not maintained three years after the intervention. This indicates that an
intervention over one year is too short for maintained overall health effects. Thus, physical
activity programs throughout the school years are needed. Our findings contribute to the
growing body of evidence that school-based interventions can increase children’s health;
however the major challenge now, is to find effective implementation strategies to transfer
such programs into the real-world setting.