Physical fitness (PF) in children and adolescents has been declining during
last decades along with physical activity (PA) level. As shown by numerous studies,
the beginning, rate and rapidity of these changes has been different in various parts of
the world as related to local environmental, social, economic, cultural, climatic, and
other life conditions. Significant relationship of these changes to health status and
prognosis was also revealed. The seriousness of this problem has been emphasized
especially that it started to appear already at very early periods of life. Studies of
children revealed increasing adiposity along with deteriorating motor abilities already
in preschool age, when the level of PA is spontaneously highest. This goes along with
earlier adiposity rebound (AR), increasing adiposity and decreasing PA level.
Preschool period is defined as one of the critical stages of development, when reduction
of natural activity can have more serious consequences than later on. In schoolchildren
and adolescents adiposity has been also increasing, and functional capacity along with
motor abilities decreasing in many coutries; positive consequences of increased PA
régimes have been greater due to the possibility for more intense exercise and sport
activities. Increased effort for intervention – which should be based on individual
somatic and functional evaluation – should start as early as possible.
Keywords: Adiposity, Adolescents, Aerobic power, Body composition (BC),
Energy expenditure (EE), Energy intake (EI), Fat-free mass (FFM), Functional
capacity, Lean body mass (LBM), Motor abilities, Physical activity (PA), Physical
fitness (PF), Preschool children, School children, Secular trends.
