Effect of timing of school enrollment on physical fitness in third graders

Abstract

Timing of initial school enrollment may vary considerably for various reasons such as early or delayed enrollment, skipped or repeated school classes. Accordingly, the age range within school grades includes older-(OTK) and younger-than-keyage (YTK) children. Hardly any information is available on the impact of timing of school enrollment on physical fitness. There is evidence from a related research topic showing large differences in academic performance between OTK and YTK children versus keyage children. Thus, the aim of this study was to compare physical fitness of OTK (N = 26,540) and YTK (N = 2586) children versus keyage children (N = 108,295) in a representative sample of German third graders. Physical fitness tests comprised cardiorespiratory endurance, coordination, speed, lower, and upper limbs muscle power. Predictions of physical fitness performance for YTK and OTK children were estimated using data from keyage children by taking age, sex, school, and assessment year into account. Data were annually recorded between 2011 and 2019. The difference between observed and predicted z-scores yielded a delta z-score that was used as a dependent variable in the linear mixed models. Findings indicate that OTK children showed poorer performance compared to keyage children, especially in coordination, and that YTK children outperformed keyage children, especially in coordination. Teachers should be aware that OTK children show poorer physical fitness performance compared to keyage children.

Physical fitness of primary school children differs depending on their timing of school enrollment

“…In a sample of 108,295 keyage third-graders from nine cohorts, the age-related gains were different for the five components, but statistically parallel for boys and girls. However, OTK third-graders (i.e., between 9.0 and 10.0 years old) exhibited significantly poorer physical fitness compared to what would be expected for their age 23 . Using the growth rates of keyage boys and girls, Fühner et al 23 predicted the performance of 26,540 OTK third-graders with a linear mixed effects model (i.e., LMM; taking into account school- and cohort-related random effects) and compared the observed physical fitness with test scores extrapolated from the LMM.…”

“…However, OTK third-graders (i.e., between 9.0 and 10.0 years old) exhibited significantly poorer physical fitness compared to what would be expected for their age 23 . Using the growth rates of keyage boys and girls, Fühner et al 23 predicted the performance of 26,540 OTK third-graders with a linear mixed effects model (i.e., LMM; taking into account school- and cohort-related random effects) and compared the observed physical fitness with test scores extrapolated from the LMM. In this cross-sectional study, OTK children performed below their predicted performance in all fitness tests (i.e., 6-min run test, star-run coordination test, 20-m sprint, standing long jump, and ball-push test).…”

“…These hypotheses cannot be tested using within-grade cross-sectional data such as those reported in previous research 23 , 24 . From within-grade cross-sectional data, we cannot determine whether the observed physical fitness of OTK children indeed indicates a delayed physical fitness development, or is due to physiological or psychological changes occurring in the tenth year of life.…”

“…A strong predictor for physical fitness in childhood is children’s age 22 , and there is evidence that physical fitness may vary depending on the timing of school enrollment 23 , 24 . The same school grade spans a wide age range of children due to factors such as timing of school enrollment or the skipping or repetition of a grade.…”

“…An alternative hypothesis for the lower physical fitness of OTK children relative to their predicted performance, is that physiological changes due to biological maturation (e.g., rise of circulating anabolic hormones and changes in body composition 33 ) or due to psychological factors (e.g., motivation) cause a somewhat abrupt stagnation of physical fitness development in the tenth year of life. Thus, if fitness development slowed down after the age of 9.0 years, the extrapolated test scores based on data from children aged 8.0–9.0 years in the analyses conducted by Fühner et al 23 would overestimate the performance of children who are one year older. The observed performance of OTK children aged 9.0–10.0 years might actually indicate ‘normal’ physical fitness development during this short time span, instead of the reported physical fitness deficit.…”