Previous research has shown that children who were enrolled according to the legal key date (i.e.... more Previous research has shown that children who were enrolled according to the legal key date (i.e., keyage children, between eight and nine years in third grade) exhibit a linear physical fitness development in the ninth year of life. In contrast, children who were enrolled with a delay (i.e., older-than-keyage children, OTK, between nine and ten years in third grade) exhibited a lower physical fitness compared to what would be expected for their age. In these cross-sectional studies, age and timing of school enrollment were confounded. In the present longitudinal study, we compared keyage and OTK children at the same age to separately examine effects of timing of school enrollment and age on six physical fitness components: cardiorespiratory endurance (i.e., 6-min run), coordination (i.e., star-run), speed (20-m sprint), power of lower (i.e., powerLOW, standing long jump) and upper (i.e., powerUP, ball-push test) limbs, and static balance (i.e., one-legged-stance test with eyes closed). 1,274 children (i.e., 1,030 keyage and 244 OTK children; 14,516 test scores) from 32 schools were tested in third grade and retested one year later in fourth grade. Both, keyage and OTK children, exhibited a positive longitudinal development in all six fitness components. However, keyage children outperformed age-matched OTK children (both groups on average 9.5 years old) in all six fitness tests. In a post-hoc exploratory analysis, we tested the assumption that some OTK children are biologically younger than indicated by their chronological age. Specifically, one reason for a delayed enrollment could be a child’s perceived biological age at the school-entry exam. In this case, chronological age would correlate negatively with biological age of OTK children. Indeed, a simple reflection of chronological age brought the developmental rate of the chronologically youngest OTK children in line with the one observed for keyage children, but did not eliminate all differences. The mapping of chronological and biological age of OTK children and other possible reasons for lower physical fitness of OTK children remain a task for future research.
Journal of Strength and Conditioning Research, Aug 21, 2020
Chaouachi, A, Ben Othman, A, Chaouachi, M, Hechmi, A, Farthing, JP, Granacher, U, and Behm, DG. C... more Chaouachi, A, Ben Othman, A, Chaouachi, M, Hechmi, A, Farthing, JP, Granacher, U, and Behm, DG. Comparison of cross-education and global training effects in adults and youth after unilateral strength training. J Strength Cond Res 36(8): 2121–2131, 2022—Youth strength training research examining contralateral, homologous (cross-education), and heterologous (global training) effects after unilateral training have provided mixed results and the relationship to adults has not been compared. The objective was to compare adult and youth cross-education and global training effects on dominant and nondominant limb testing. Initially, 15 men and 15 prepubertal boys volunteered for each unilateral chest press (CP), handgrip training, and control groups (n = 89). Individuals trained their dominant limb 3 times per week for 8 weeks and had their dominant and nondominant limbs tested for CP and leg press 1 repetition maximum (1RM), handgrip, knee extension and flexion, and elbow extension and flexion maximum voluntary isometric contractions (MVICs). Adult CP training gains were significantly greater than youth with lower-body testing (p = 0.002–0.06), whereas youth CP training gains exceeded adults with upper-body tests (p = 0.03–0.07). Training specificity was evident with greater CP 1RM increases with CP vs. handgrip training for both youth (p < 0.0001) and adults (p < 0.0001). Handgrip training elicited greater gains in handgrip MVICs compared with other strength tests (p < 0.0001). In conclusion, only contralateral CP 1RM showed a training advantage for unilateral CP over unilateral handgrip training. Adults showed greater gains with lower-body testing, whereas youth showed greater gains with upper-body testing.
Primary school children perform parts of their everyday activities while carrying school supplies... more Primary school children perform parts of their everyday activities while carrying school supplies and being involved in attention-demanding situations. Twenty-eight children (8-10 years old) performed a 1-legged stance and a 10 m walking test under single- and dual-task situations in unloaded (i.e., no backpack) and loaded conditions (i.e., backpack with 20% of body mass). Results showed that load carriage did not significantly influence children's standing and walking performance (all p > .05), while divided attention affected all proxies of walking (all p < .001). Last, no significant load by attention interactions was detected. The single application of attentional but not load demand negatively affects children's walking performance. A combined application of both did not further deteriorate their gait behavior.
The Frontiers Research Topic entitled "Neuromuscular Training and Adaptations in Youth Athle... more The Frontiers Research Topic entitled "Neuromuscular Training and Adaptations in Youth Athletes" contains one editorial and 22 articles in the form of original work, narrative and systematic reviews and meta-analyses. From a performance and health-related standpoint, neuromuscular training stimulates young athletes' physical development and it builds a strong foundation for later success as an elite athlete. The 22 articles provide current scientific knowledge on the effectiveness of neuromuscular training in young athletes
Scandinavian Journal of Medicine & Science in Sports, Jul 26, 2016
The purpose of this study was to examine whether drop height‐induced changes in leg muscle activi... more The purpose of this study was to examine whether drop height‐induced changes in leg muscle activity during drop jumps (DJ) are additionally modulated by surface condition. Twenty‐four healthy participants (23.7 ± 1.8 years) performed DJs on a force plate on stable, unstable, and highly unstable surfaces using different drop heights (i.e., 20 cm, 40 cm, 60 cm). Electromyographic (EMG) activity of soleus (SOL), gastrocnemius (GM), tibialis anterior (TA) muscles and coactivation of TA/SOL and TA/GM were analyzed for time intervals 100 ms prior to ground contact (preactivation) and 30–60 ms after ground contact [short latency response (SLR)]. Increasing drop heights resulted in progressively increased SOL and GM activity during preactivation and SLR (P < 0.01; 1.01 ≤ d ≤ 5.34) while TA/SOL coactivation decreased (P < 0.05; 0.51 ≤ d ≤ 3.01). Increasing surface instability produced decreased activities during preactivation (GM) and SLR (GM, SOL) (P < 0.05; 1.36 ≤ d ≤ 4.30). Coactivation increased during SLR (P < 0.05; 1.50 ≤ d ≤ 2.58). A significant drop height × surface interaction was observed for SOL during SLR. Lower SOL activity was found on unstable compared to stable surfaces for drop heights ≥40 cm (P < 0.05; 1.25 ≤ d ≤ 2.12). Findings revealed that instability‐related changes in activity of selected leg muscles are minimally affected by drop height.
Background In spring of 2020, the Sars-CoV-2 incidence rate increased rapidly in Germany and arou... more Background In spring of 2020, the Sars-CoV-2 incidence rate increased rapidly in Germany and around the world. Throughout the next 2 years, schools were temporarily closed and social distancing measures were put in place to slow the spread of the Covid-19 virus. Did these social restrictions and temporary school lockdowns affect children’s physical fitness? The EMOTIKON project annually tests the physical fitness of all third-graders in the Federal State of Brandenburg, Germany. The tests assess cardiorespiratory endurance (6-min-run test), coordination (star-run test), speed (20-m sprint test), lower (powerLOW, standing long jump test), and upper (powerUP, ball-push test) limbs muscle power, and static balance (one-legged stance test with eyes closed). A total of 125,893 children were tested in the falls from 2016 to 2022. Primary analyses focused on 98,510 keyage third-graders (i.e., school enrollment according to the legal key date, aged 8 to 9 years) from 515 schools. Secondary ...
Die Muskelkraft stellt eine wesentliche Grundlage der korperlichen Leistungsfahigkeit dar, um spo... more Die Muskelkraft stellt eine wesentliche Grundlage der korperlichen Leistungsfahigkeit dar, um sport- und alltagsmotorische Bewegungsfertigkeiten zu erlernen, auszufuhren und zu verbessern. Gleichzeitig bedingt ein effektives und gesundheitsforderliches Training der Kraft eine korrekte Ausfuhrung der Trainingsubungen bzw. der Bewegungskoordination. Ohne ausreichende Kraft ware es auch nicht moglich, eine Ausdauerleistung okonomisch und gesundheitssteigernd zu erbringen. Die Diagnostik und das Training der Kraft sowie der Schnelligkeit, die eine aus Kraft und Koordination zusammengesetzte Einflussgrose der korperlichen Leistungsfahigkeit darstellt, sind bedeutsame Komponenten fur eine wunschenswerte langfristige korperliche Entwicklung von Kindern und Jugendlichen. In diesem Kapitel werden die wesentlichen Leistungs- und Entwicklungskriterien sowie Trainingsempfehlungen zusammengefasst.
Journal of Strength and Conditioning Research, 2021
Ramirez-Campillo, R, Garcia-Pinillos, F, Chaabene, H, Moran, J, Behm, DG, and Granacher, U. Effec... more Ramirez-Campillo, R, Garcia-Pinillos, F, Chaabene, H, Moran, J, Behm, DG, and Granacher, U. Effects of plyometric jump training on electromyographic activity and its relationship to strength and jump performance in healthy trained and untrained populations: a systematic review of randomized controlled trials. J Strength Cond Res 35(7): 2053–2065, 2021—This systematic review analyzed the effects of plyometric jump training (PJT) on muscle activation assessed with surface electromyography during the performance of strength and jumping tasks in healthy populations across the lifespan. A systematic literature search was conducted in the electronic databases PubMed/MEDLINE, Web of Science, and SCOPUS. Only randomized controlled studies were eligible to be included in this study. Our search identified 17 studies comprising 23 experimental groups and 266 subjects aged 13–73 years, which were eligible for inclusion. The included studies achieved a median Physiotherapy Evidence Database scor...
Many adults older than 60 yr experience mobility limitations. Although physical exercise improves... more Many adults older than 60 yr experience mobility limitations. Although physical exercise improves older adults' mobility, differences in baseline mobility produce large variations in individual responses to interventions, and these responses could further vary by the type and dose of exercise. Here, we propose an exercise prescription model for older adults based on their current mobility status.
Several studies have investigated the effects of music on both submaximal and maximal exercise pe... more Several studies have investigated the effects of music on both submaximal and maximal exercise performance at a constant work-rate. However, there is a lack of research that has examined the effects of music on the pacing strategy during self-paced exercise. The aim of this study was to examine the effects of preferred music on performance and pacing during a 6 min run test (6-MSPRT) in young male adults. Twenty healthy male participants volunteered for this study. They performed two randomly assigned trials (with or without music) of a 6-MSPRT three days apart. Mean running speed, the adopted pacing strategy, total distance covered (TDC), peak and mean heart rate (HRpeak, HRmean), blood lactate (3 min after the test), and rate of perceived exertion (RPE) were measured. Listening to preferred music during the 6-MSPRT resulted in significant TDC improvement (Δ10%; p = 0.016; effect size (ES) = 0.80). A significantly faster mean running speed was observed when listening to music compa...
Previous research has shown that children who were enrolled according to the legal key date (i.e.... more Previous research has shown that children who were enrolled according to the legal key date (i.e., keyage children, between eight and nine years in third grade) exhibit a linear physical fitness development in the ninth year of life. In contrast, children who were enrolled with a delay (i.e., older-than-keyage children, OTK, between nine and ten years in third grade) exhibited a lower physical fitness compared to what would be expected for their age. In these cross-sectional studies, age and timing of school enrollment were confounded. In the present longitudinal study, we compared keyage and OTK children at the same age to separately examine effects of timing of school enrollment and age on six physical fitness components: cardiorespiratory endurance (i.e., 6-min run), coordination (i.e., star-run), speed (20-m sprint), power of lower (i.e., powerLOW, standing long jump) and upper (i.e., powerUP, ball-push test) limbs, and static balance (i.e., one-legged-stance test with eyes closed). 1,274 children (i.e., 1,030 keyage and 244 OTK children; 14,516 test scores) from 32 schools were tested in third grade and retested one year later in fourth grade. Both, keyage and OTK children, exhibited a positive longitudinal development in all six fitness components. However, keyage children outperformed age-matched OTK children (both groups on average 9.5 years old) in all six fitness tests. In a post-hoc exploratory analysis, we tested the assumption that some OTK children are biologically younger than indicated by their chronological age. Specifically, one reason for a delayed enrollment could be a child’s perceived biological age at the school-entry exam. In this case, chronological age would correlate negatively with biological age of OTK children. Indeed, a simple reflection of chronological age brought the developmental rate of the chronologically youngest OTK children in line with the one observed for keyage children, but did not eliminate all differences. The mapping of chronological and biological age of OTK children and other possible reasons for lower physical fitness of OTK children remain a task for future research.
Journal of Strength and Conditioning Research, Aug 21, 2020
Chaouachi, A, Ben Othman, A, Chaouachi, M, Hechmi, A, Farthing, JP, Granacher, U, and Behm, DG. C... more Chaouachi, A, Ben Othman, A, Chaouachi, M, Hechmi, A, Farthing, JP, Granacher, U, and Behm, DG. Comparison of cross-education and global training effects in adults and youth after unilateral strength training. J Strength Cond Res 36(8): 2121–2131, 2022—Youth strength training research examining contralateral, homologous (cross-education), and heterologous (global training) effects after unilateral training have provided mixed results and the relationship to adults has not been compared. The objective was to compare adult and youth cross-education and global training effects on dominant and nondominant limb testing. Initially, 15 men and 15 prepubertal boys volunteered for each unilateral chest press (CP), handgrip training, and control groups (n = 89). Individuals trained their dominant limb 3 times per week for 8 weeks and had their dominant and nondominant limbs tested for CP and leg press 1 repetition maximum (1RM), handgrip, knee extension and flexion, and elbow extension and flexion maximum voluntary isometric contractions (MVICs). Adult CP training gains were significantly greater than youth with lower-body testing (p = 0.002–0.06), whereas youth CP training gains exceeded adults with upper-body tests (p = 0.03–0.07). Training specificity was evident with greater CP 1RM increases with CP vs. handgrip training for both youth (p < 0.0001) and adults (p < 0.0001). Handgrip training elicited greater gains in handgrip MVICs compared with other strength tests (p < 0.0001). In conclusion, only contralateral CP 1RM showed a training advantage for unilateral CP over unilateral handgrip training. Adults showed greater gains with lower-body testing, whereas youth showed greater gains with upper-body testing.
Primary school children perform parts of their everyday activities while carrying school supplies... more Primary school children perform parts of their everyday activities while carrying school supplies and being involved in attention-demanding situations. Twenty-eight children (8-10 years old) performed a 1-legged stance and a 10 m walking test under single- and dual-task situations in unloaded (i.e., no backpack) and loaded conditions (i.e., backpack with 20% of body mass). Results showed that load carriage did not significantly influence children's standing and walking performance (all p > .05), while divided attention affected all proxies of walking (all p < .001). Last, no significant load by attention interactions was detected. The single application of attentional but not load demand negatively affects children's walking performance. A combined application of both did not further deteriorate their gait behavior.
The Frontiers Research Topic entitled "Neuromuscular Training and Adaptations in Youth Athle... more The Frontiers Research Topic entitled "Neuromuscular Training and Adaptations in Youth Athletes" contains one editorial and 22 articles in the form of original work, narrative and systematic reviews and meta-analyses. From a performance and health-related standpoint, neuromuscular training stimulates young athletes' physical development and it builds a strong foundation for later success as an elite athlete. The 22 articles provide current scientific knowledge on the effectiveness of neuromuscular training in young athletes
Scandinavian Journal of Medicine & Science in Sports, Jul 26, 2016
The purpose of this study was to examine whether drop height‐induced changes in leg muscle activi... more The purpose of this study was to examine whether drop height‐induced changes in leg muscle activity during drop jumps (DJ) are additionally modulated by surface condition. Twenty‐four healthy participants (23.7 ± 1.8 years) performed DJs on a force plate on stable, unstable, and highly unstable surfaces using different drop heights (i.e., 20 cm, 40 cm, 60 cm). Electromyographic (EMG) activity of soleus (SOL), gastrocnemius (GM), tibialis anterior (TA) muscles and coactivation of TA/SOL and TA/GM were analyzed for time intervals 100 ms prior to ground contact (preactivation) and 30–60 ms after ground contact [short latency response (SLR)]. Increasing drop heights resulted in progressively increased SOL and GM activity during preactivation and SLR (P < 0.01; 1.01 ≤ d ≤ 5.34) while TA/SOL coactivation decreased (P < 0.05; 0.51 ≤ d ≤ 3.01). Increasing surface instability produced decreased activities during preactivation (GM) and SLR (GM, SOL) (P < 0.05; 1.36 ≤ d ≤ 4.30). Coactivation increased during SLR (P < 0.05; 1.50 ≤ d ≤ 2.58). A significant drop height × surface interaction was observed for SOL during SLR. Lower SOL activity was found on unstable compared to stable surfaces for drop heights ≥40 cm (P < 0.05; 1.25 ≤ d ≤ 2.12). Findings revealed that instability‐related changes in activity of selected leg muscles are minimally affected by drop height.
Background In spring of 2020, the Sars-CoV-2 incidence rate increased rapidly in Germany and arou... more Background In spring of 2020, the Sars-CoV-2 incidence rate increased rapidly in Germany and around the world. Throughout the next 2 years, schools were temporarily closed and social distancing measures were put in place to slow the spread of the Covid-19 virus. Did these social restrictions and temporary school lockdowns affect children’s physical fitness? The EMOTIKON project annually tests the physical fitness of all third-graders in the Federal State of Brandenburg, Germany. The tests assess cardiorespiratory endurance (6-min-run test), coordination (star-run test), speed (20-m sprint test), lower (powerLOW, standing long jump test), and upper (powerUP, ball-push test) limbs muscle power, and static balance (one-legged stance test with eyes closed). A total of 125,893 children were tested in the falls from 2016 to 2022. Primary analyses focused on 98,510 keyage third-graders (i.e., school enrollment according to the legal key date, aged 8 to 9 years) from 515 schools. Secondary ...
Die Muskelkraft stellt eine wesentliche Grundlage der korperlichen Leistungsfahigkeit dar, um spo... more Die Muskelkraft stellt eine wesentliche Grundlage der korperlichen Leistungsfahigkeit dar, um sport- und alltagsmotorische Bewegungsfertigkeiten zu erlernen, auszufuhren und zu verbessern. Gleichzeitig bedingt ein effektives und gesundheitsforderliches Training der Kraft eine korrekte Ausfuhrung der Trainingsubungen bzw. der Bewegungskoordination. Ohne ausreichende Kraft ware es auch nicht moglich, eine Ausdauerleistung okonomisch und gesundheitssteigernd zu erbringen. Die Diagnostik und das Training der Kraft sowie der Schnelligkeit, die eine aus Kraft und Koordination zusammengesetzte Einflussgrose der korperlichen Leistungsfahigkeit darstellt, sind bedeutsame Komponenten fur eine wunschenswerte langfristige korperliche Entwicklung von Kindern und Jugendlichen. In diesem Kapitel werden die wesentlichen Leistungs- und Entwicklungskriterien sowie Trainingsempfehlungen zusammengefasst.
Journal of Strength and Conditioning Research, 2021
Ramirez-Campillo, R, Garcia-Pinillos, F, Chaabene, H, Moran, J, Behm, DG, and Granacher, U. Effec... more Ramirez-Campillo, R, Garcia-Pinillos, F, Chaabene, H, Moran, J, Behm, DG, and Granacher, U. Effects of plyometric jump training on electromyographic activity and its relationship to strength and jump performance in healthy trained and untrained populations: a systematic review of randomized controlled trials. J Strength Cond Res 35(7): 2053–2065, 2021—This systematic review analyzed the effects of plyometric jump training (PJT) on muscle activation assessed with surface electromyography during the performance of strength and jumping tasks in healthy populations across the lifespan. A systematic literature search was conducted in the electronic databases PubMed/MEDLINE, Web of Science, and SCOPUS. Only randomized controlled studies were eligible to be included in this study. Our search identified 17 studies comprising 23 experimental groups and 266 subjects aged 13–73 years, which were eligible for inclusion. The included studies achieved a median Physiotherapy Evidence Database scor...
Many adults older than 60 yr experience mobility limitations. Although physical exercise improves... more Many adults older than 60 yr experience mobility limitations. Although physical exercise improves older adults' mobility, differences in baseline mobility produce large variations in individual responses to interventions, and these responses could further vary by the type and dose of exercise. Here, we propose an exercise prescription model for older adults based on their current mobility status.
Several studies have investigated the effects of music on both submaximal and maximal exercise pe... more Several studies have investigated the effects of music on both submaximal and maximal exercise performance at a constant work-rate. However, there is a lack of research that has examined the effects of music on the pacing strategy during self-paced exercise. The aim of this study was to examine the effects of preferred music on performance and pacing during a 6 min run test (6-MSPRT) in young male adults. Twenty healthy male participants volunteered for this study. They performed two randomly assigned trials (with or without music) of a 6-MSPRT three days apart. Mean running speed, the adopted pacing strategy, total distance covered (TDC), peak and mean heart rate (HRpeak, HRmean), blood lactate (3 min after the test), and rate of perceived exertion (RPE) were measured. Listening to preferred music during the 6-MSPRT resulted in significant TDC improvement (Δ10%; p = 0.016; effect size (ES) = 0.80). A significantly faster mean running speed was observed when listening to music compa...
Background There is evidence that physical fitness of children and adolescents (particularly card... more Background There is evidence that physical fitness of children and adolescents (particularly cardiorespiratory endurance) has declined globally over the past decades. Ever since the first reports on negative trends in physical fitness, efforts have been undertaken by for instance the World Health Organization (WHO) to promote physical activity and fitness in children and adolescents. Therefore, it is timely to re-analyze the literature to examine whether previous reports on secular declines in physical fitness are still detectable or whether they need to be updated
.Objectives The objective of this systematic review is to provide an ‘update’ on secular trends in selected components of physical fitness (i.e., cardiorespiratory endurance, relative muscle strength, proxies of muscle power, speed) in children and adolescents aged 6–18 years.
Data Sources A systematic computerized literature search was conducted in the electronic databases PubMed and Web of Science to locate studies that explicitly reported secular trends in physical fitness of children and adolescents.Study Eligibility Criteria Studies were included in this systematic review if they examined secular trends between at least two time points across a minimum of 5 years. In addition, they had to document secular trends in any measure of cardiorespira-tory endurance, relative muscle strength, proxies of muscle power or speed in apparently healthy children and adolescents aged 6–18 years.
Study Appraisal and Synthesis Methods The included studies were coded for the following criteria: nation, physical fitness component (cardiorespiratory endurance, relative muscle strength, proxies of muscle power, speed), chronological age, sex (boys vs. girls), and year of assessment. Scores were standardized (i.e., converted to z scores) with sample-weighted means and standard deviations, pooled across sex and year of assessment within cells defined by study, test, and children’s age.
Results The original search identified 524 hits. In the end, 22 studies met the inclusion criteria for review. The observation period was between 1972 and 2015. Fifteen of the 22 studies used tests for cardiorespiratory endurance, eight for relative muscle strength, eleven for proxies of muscle power, and eight for speed. Measures of cardiorespiratory endurance exhibited a large initial increase and an equally large subsequent decrease, but the decrease appears to have reached a floor for all children between 2010 and 2015. Measures of relative muscle strength showed a general trend towards a small increase. Measures of proxies of muscle power indicated an overall small negative quadratic trend. For measures of speed, a small-to-medium increase was observed in recent years.Limitations Biological maturity was not considered in the analysis because biological maturity was not reported in most included studies.
Conclusions Negative secular trends were particularly found for cardiorespiratory endurance between 1986 and 2010–12, irrespective of sex. Relative muscle strength and speed showed small increases while proxies of muscle power declined. Although the negative trend in cardiorespiratory endurance appears to have reached a floor in recent years, because of its association with markers of health, we recommend further initiatives in PA and fitness promotion for children and adoles-cents. More specifically, public health efforts should focus on exercise that increases cardiorespiratory endurance to prevent adverse health effects (i.e., overweight and obesity) and muscle strength to lay a foundation for motor skill learning
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Papers by Urs Granacher
.Objectives The objective of this systematic review is to provide an ‘update’ on secular trends in selected components of physical fitness (i.e., cardiorespiratory endurance, relative muscle strength, proxies of muscle power, speed) in children and adolescents aged 6–18 years.
Data Sources
A systematic computerized literature search was conducted in the electronic databases PubMed and Web of Science to locate studies that explicitly reported secular trends in physical fitness of children and adolescents.Study Eligibility Criteria Studies were included in this systematic review if they examined secular trends between at least two time points across a minimum of 5 years. In addition, they had to document secular trends in any measure of cardiorespira-tory endurance, relative muscle strength, proxies of muscle power or speed in apparently healthy children and adolescents aged 6–18 years.
Study Appraisal and Synthesis Methods
The included studies were coded for the following criteria: nation, physical fitness component (cardiorespiratory endurance, relative muscle strength, proxies of muscle power, speed), chronological age, sex (boys vs. girls), and year of assessment. Scores were standardized (i.e., converted to z scores) with sample-weighted means and standard deviations, pooled across sex and year of assessment within cells defined by study, test, and children’s age.
Results
The original search identified 524 hits. In the end, 22 studies met the inclusion criteria for review. The observation period was between 1972 and 2015. Fifteen of the 22 studies used tests for cardiorespiratory endurance, eight for relative muscle strength, eleven for proxies of muscle power, and eight for speed. Measures of cardiorespiratory endurance exhibited a large initial increase and an equally large subsequent decrease, but the decrease appears to have reached a floor for all children between 2010 and 2015. Measures of relative muscle strength showed a general trend towards a small increase. Measures of proxies of muscle power indicated an overall small negative quadratic trend. For measures of speed, a small-to-medium increase was observed in recent years.Limitations Biological maturity was not considered in the analysis because biological maturity was not reported in most included studies.
Conclusions
Negative secular trends were particularly found for cardiorespiratory endurance between 1986 and 2010–12, irrespective of sex. Relative muscle strength and speed showed small increases while proxies of muscle power declined. Although the negative trend in cardiorespiratory endurance appears to have reached a floor in recent years, because of its association with markers of health, we recommend further initiatives in PA and fitness promotion for children and adoles-cents. More specifically, public health efforts should focus on exercise that increases cardiorespiratory endurance to prevent adverse health effects (i.e., overweight and obesity) and muscle strength to lay a foundation for motor skill learning