Background and methods There is a paucity of data on contemporary secular trends on the different aspects of physical fitness in school-aged children and adolescents. This study presents the largest ever data set on changes in fitness between 1992, 2002 and 2012 for both genders of schoolchildren aged 11–18 years (n=16 199). Eurofit test battery was used to assess the balance, flexibility, muscular strength and power, agility and cardiorespiratory fitness. Anthropometrics were also measured and body mass index (BMI) was calculated.

Results The study has shown loss of flexibility, leg muscle power, upper body strength and cardiorespiratory fitness between 1992 and 2012, although there was an improvement in abdominal muscle strength in girls, agility in boys and balance in both genders during the same period. At large, negative trends in aspects of fitness seen between 1992 and 2002 have not slowed down between 2002 and 2012. Positive trends in agility and abdominal muscle strength seen before 2002 have regressed or were reversed between 2002 and 2012, while balance continued to improve at increased pace. While the BMI continued to increase in all groups, analysis of covariance has shown that it was not the main cause of changes in fitness.

Conclusions The general decline in physical fitness in Lithuanian schoolchildren observed between 1992 and 2002 continued between 2002 and 2012, although some aspects of fitness showed a positive trend. If this general negative trend continues, it will compromise the well-being of future adults and create a serious economic burden on the society.