Table 1.

Summary of the literature analysis.

Author	Title	Participants	Aims	Methodology	Main Results	Country	Trend
Ao, D. et al. [23]	Trends in Physical Fitness Among 12-Year-Old Children in Urban and Rural Areas During the Social Transformation Period in China	N = 136,539: 34,238 (in 1985); 11,664 (in 1991); 17,485 (in 1995); 18,057 (in 2000); 19,254 (in 2005); 17,962 (in 2010); and 17,906 (in 2014). Aged 12.	The study examines trends spanning 29 years (1985–2014) in body size and performance within physical fitness tests among 12-year-old Chinese children residing in both urban and rural areas.	The analysis draws on data obtained from seven cross-sectional surveys conducted as part of the China National Survey of Student Body Constitution and Health. These surveys encompass anthropometric measurements and assessments of physical performance among 12-year-old Chinese children residing in both rural and urban areas.	The physical fitness levels of children in both urban and rural areas have shown a consistent decline since the year 2000.	China	Physical fitness	ꜜ
Colley, et al. [24]	Trends in physical fitness among Canadian children and young people	N = 6284: 2081 (2007–2009), 2133 (2009–2011), 2070 (2016–2017). Aged 6–19 in 10– year period.	To examine the course of time of fitness.	Tests for measurements of body composition, muscle strength and power, flexibility, and cardiorespiratory fitness.	Physical fitness measurements varied across three cycles (2007–2009, 2009–2011, and 2016–2017) by gender and age group. Significant differences were found between cycles. There have been declines in cardiorespiratory fitness among boys aged 8 to 14 years. Additionally, grip strength has decreased in boys aged 11 to 19 years. However, flexibility remained relatively stable over time, with a slight improvement noted in girls aged 6 to 10 years.	Canada	Cardiorespiratory fitness and grip strength	ꜜ
							Flexibility	=ꜛ
Costa, et al. [25]	Secular Trends in Anthropometrics and Physical Fitness of Young Portuguese School-Aged Children	N = 1819 students, (881 males and 938 females). Age = 10 and 11 years old. Evaluation = during their 5th and 6th scholar grades throughout the entire 20-year timeframe.	Objective: to assess Portuguese children’s physical fitness and secular trends in anthropometrics.	An ANCOVA (Analysis of Covariance) model was employed to examine the variability in anthropometric measures (weight, height, and body mass index) and physical fitness indicators (horizontal jump, curl-up, sprint times, sit and reach) over four consecutive five-year periods (1993–1998; 1998–2003; 2003–2008; 2008–2013).	Throughout the past 20 years, heavier boys and more obese girls were present in the 5th and 6th grades. There was a presence of taller girls (up to the third grade). In tests of core strength and sprint times, both boys and girls did well, but as the years went by, flexibility declined. Average jumping ability remained unchanged for both sexes.	Portugal	Core strength test and sprint times	ꜛ
							Body composition	ꜜ
							Flexibility	ꜜ
							Jumping performance	=
Filippone, et al. [26]	Secular trend of involution of motor skills in school age	N = 1137 students (586 males and 551 females) of the secondary school of the 1st degree of Bolzano, which was assessed in the 1st class in 1989–2004.	To verify the existence of centuries-old trends of involution of motor skills.	Longitudinal–cross-sectional study	Secular trend of involution of aerobic resistance associated with an involution of coordinating performance. Secular trend of involution of aerobic endurance associated with involution of co-ordinative performance.	Italy	Aerobic resistance	ꜜ
							Coordination performance	ꜜ
Iannotti and Wang, [27]	Trends in Physical Activity, Sedentary Behavior, Diet, and BMI Among US teenagers, 2001–2009	N = total of 479,674 students; 49% male; aged 11 years (N = 156,383); 13 years (N = 163,729); 15 years (N = 159,562).	To examine 8-year trends in these behaviours in US teenagers ages 11 to 16.	The Health Behaviour Survey of School-Age Children was administered every four years, with the same questions assessing BMI, physical activity, sedentary behaviour, and eating behaviour at each grade level. Logistic and linear regression analysis controlling for age, gender, race/ethnicity, and family affluence were conducted to account for sampling design.	Significant increments were identified in the number of days with at least 60 min of PA, daily fruit and vegetable consumption, breakfast on weekdays and weekends, and BMI.	USA	Daily minutes PA	ꜛ
							Body composition	ꜜ
Kasović, et al. [28]	Secular trends in health-related physical fitness among 11–14-year-old Croatian children and teenagers from 1999 to 2014	N = 5077 children (50.8% female) and teenagers between the ages of 11 and 14 were recruited by five elementary schools.	Investigating secular trends in 7–14-year-old Croatian children and teenagers from 1999 and 2014 of health-related physical fitness	Cross-sectional study	Boys outperformed girls in all physical fitness tests except for the sit and reach test. Between 1999 and 2014, boys experienced increases in body size, upper body strength, and coordination/agility while observing declines in flexibility, lower body power, and cardiorespiratory fitness. Conversely, during the same period, girls demonstrated increases in body size, lower body power, upper body strength, coordination/agility, and flexibility, but showed a decrease in cardiorespiratory fitness.	Croatia	Physical fitness	ꜛ
							Sit and reach test	ꜜ
							Boys: Body size	ꜜ
							Upper body strength and coordination/agility	ꜛ
							Cardiorespiratory fitness	ꜜ
							Girls: Body size	ꜜ
							Lower body power, upper body strength, coordination/agility, and flexibility	ꜛ
							Cardiorespiratory fitness	ꜜ
Radulovic, et al. [29]	Secular trends in physical fitness of Slovenian boys and girls aged 7 to 15 years from 1989 to 2019: a population-based study.	N = 4,256,930; study period: 1989–2019.	To assess the trend of multiple components of physical fitness in children and young people during the entire educational cycle.	Population-based study: the SLOfit test battery consists of the following anthropometric measurements and fitness tests: BMI, triceps subcutaneous fat, 60 s abdominal crunches, 600-metre run, stand-and-reach, bent arm push-ups (BAHs), standing long jump, 60-metre run, backwards hurdle run, and 20 s arm plateau beat.	Increases in body mass index and skin triceps were recorded in all age groups and both sexes. A decline in cardiorespiratory efficiency was observed in each age group until the last ten years.	Slovenia	Body composition and triceps skinfold	ꜜ
							Cardiorespiratory fitness	ꜜ
Sigmundová, et al. [30]	Secular trends: a ten-year comparison of the amount and type of physical activity and inactivity of random samples of teenagers in the Czech Republic	N = 1573; random samples of teenagers (aged 14–18 years).	To estimate the trends and levels of adolescents’ PA and sedentary behaviour in the Czech Republic. To investigate the secular trends from 1998–2000 to 2008–2010 of PA by a pedometer tool and sedentary behaviour.	Two cross-sectional cohorts of adolescents after one decade. Data were collected through weekly monitoring of adolescents’ PA in 1998–2000 and 2008–2010. In the reference sample, an increase in overweight and obesity was found from 5.5% (oldest cohort, 1998–2000) to 10.4% (youngest cohort).	Overweight and obesity among Czech teenagers in the study increased from 5.5% (older cohort, 1998–2000) to 10.4% (younger cohort, 2008–2010). For boys, there were no relevant variations in the total quantity of sedentary behaviour between the cohorts. For girls, the total amount of sedentary behaviour increased significantly for the older cohort (1998–2000) in comparison with the younger cohort (2008–2010).	Czech Republic	Daily PA	ꜜ
							Body composition	ꜜ
Tomkinson, et al. [31]	Secular Trends in the Aerobic Fitness Test Performance and Body Mass Index of Korean Children and Teenagers (1968–2000)	N = 22,127,265 children aged 6–18 years.	Data from 600–1200 m distance running tests conducted between 1968 and 2000 by Koreans aged 6–18 years were analysed.	Three main methods. (1) The authors personally contacted the Korean Ministry of Education and the Ministry of Culture and Tourism to request relevant published and unpublished works. (2) All relevant references in the studies were followed when obtaining published reports. (3) Online research bibliographic databases and the Korean National Sports University library catalogue, using keywords fitness, performance, endurance, distance run, and aerobic.	Between 1968 and 1984, there was a gradual decline in aerobic capacity among Korean children, with a decrease averaging rate of 0.26% per year. However, after 1984, this decline accelerated significantly, averaging 0.80% per year. Moreover, the rate of decline was found to be higher among boys, younger children, and those residing outside the capital city of Seoul. Changes in running ability among Korean children exhibited a similar pattern to the alterations observed in estimated body mass index. Korean children’s performance on aerobic fitness tests sharply declined in comparison to children from other countries, a trend that coincided with an increase in estimated body mass index among Korean children.	Korea	Aerobic performance	ꜜ
							Body composition	ꜜ
							Running performance	ꜜ
Venckunas, et al. [32]	Secular trends in physical fitness and body size in Lithuanian children and teenagers between 1992 and 2012	N = 16,199 (8131 females, 8068 males); 5775 in 1992, 5325 in 2002, 5099 in 2012; aged 11–18 years.	To assess in Lithuanian schoolchildren between 1992 and 2002 and 2002 and 2012 the general decline in physical fitness.	The study used a Eurofit test battery to evaluate balance, flexibility, strength and muscle power, agility, and cardiorespiratory shape. Anthropometry (BMI) calculated.	There was a reduction observed in upper body strength, leg muscle power, flexibility, and cardiorespiratory fitness between the years, 1992 and 2012. Over the same time period, balance improved in both genders, boys’ agility increased, and girls’ abdominal muscle strength increased. Between 2002 and 2012, the detrimental trends in fitness-related aspects that had been noticed between 1992 and 2002 continued. While the improvement in balance continued at a faster pace, the previously observed positive trends in agility and abdominal muscle strength, noted before 2002, either regressed or reversed between 2002 and 2012.	Lithuania	Flexibility, leg muscle power, upper body strength, and cardiorespiratory fitness	ꜜ
							Abdominal muscle strength	ꜜ
							Balance	ꜛ

= stable.