The role of fatness on physical fitness in adolescents with and without Down syndrome: The UP&DOWN study

Background/Objectives: Adolescents with Down syndrome (DS) exhibit higher levels of fatness and low levels of physical fitness compared with those without DS. In adolescents without DS, fatness is tightly associated with physical fitness, but this association is unclear in adolescents with DS. The aim of this study was to examine the association between several markers of fatness and physical fitness in a relative large sample of adolescents with and without DS. Subjects/Methods: A total of 111 adolescents with DS (41 females) aged 11–20 years participated in this cross-sectional study. We also included a sex-matched control group (ratio 1:2) of 222 adolescents without DS aged 12–18 years, participating in the UP&DOWN Study. The Assessing Level of Physical Activity (ALPHA) health-related fitness test battery for adolescents was used to assess fatness and physical fitness. Results: Our results show that fatness is not associated with low levels of physical fitness in adolescents with DS (that is, 3 of the 16 analyses identified differences in physical fitness variables by groups of fatness). In contrast, fatness, as expected, is associated with levels of physical fitness in adolescents without DS (that is, 13 of the 16 analyses identified differences in physical fitness variables by groups of fatness). Conclusions: The present finding contributes to new knowledge by suggesting that the role of fatness on physical fitness is different in adolescents with and without DS, and consequently, the poor levels of physical fitness in adolescents with DS may be due to the syndrome rather than the high prevalence of obesity from this population.