title: Developmental differences between boys and girls result in sex-specific physical fitness changes from fourth to fifth grade.
abstract: To better understand how developmental differences impact performance on a broad selection of common physical fitness measures, we examined changes in boys and girls from fourth to fifth grade. Subjects included 273 boys (age, 9.5 ± 0.6 years; height, 139.86 ± 7.52 cm; mass, 38.00 ± 9.55 kg) and 295 girls (age, 9.6 ± 0.5 years; height, 139.30 ± 7.19 cm; weight, 37.44 ± 9.35 kg). We compared anthropometrics, cardiorespiratory and local muscular endurance, flexibility, power, and strength. A mixed-method analysis of variance was used to compare boys and girls at the 2 time points. Pearson correlation coefficients were used to examine relationships between anthropometric and fitness measurements. Significance was set at p ≤ 0.05. Weight increased significantly (>10%) in both sexes, and girls became significantly taller than boys after growing 4.9% by fifth grade (vs. 3.5%). Both groups improved cardiorespiratory endurance and power, although boys performed better than girls at both time points. Boys were stronger in fourth grade, but girls improved more, leading to similar fifth-grade values. Girls were more flexible in fourth grade, but their significant decreases (∼32.4%) coupled with large improvements in boys (∼105%) resulted in similar fifth-grade scores. Body mass index (BMI) was positively correlated with run time regardless of grade or sex. Power was negatively correlated with BMI and run time in fourth grade. In conclusion, sex-specific differences in physical fitness are apparent before pubescence. Furthermore, this selection of measures reveals sexually dimorphic changes, which likely reflect the onset of puberty in girls. Coaches and teachers should account these developmental differences and their effects on anthropometrics and fitness in boys and girls.
authors.affiliation: 1Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, Connecticut; 2Department of Health Sciences, School of Science and Engineering, Merrimack College, North Andover, Massachusetts; 3Department of Kinesiology, University of Rhode Island, Kingston, Rhode Island; 4Department of Educational and Human Sciences, College of Education and Human Performance, University of Central Florida, Orlando, Florida; 5Department of Wellness and Fitness, Chambersburg Area School District, Chambersburg, Pennsylvania; 6Department of Human Sciences, Society and Health, University of Cassino and Lazio Meridionale, Cassino, Italy; 7Cumberland Valley Family Physicians, Chambersburg, Pennsylvania; and 8Department of Human Sciences, The Ohio State University, Columbus, Ohio.
authors.forename: Shawn D
authors.initials: SD
authors.lastname: Flanagan
authors.forename: Courtenay
authors.initials: C
authors.lastname: Dunn-Lewis
authors.forename: Disa L
authors.initials: DL
authors.lastname: Hatfield
authors.forename: Lindsay J
authors.initials: LJ
authors.lastname: Distefano
authors.forename: Maren S
authors.initials: MS
authors.lastname: Fragala
authors.forename: Mark
authors.initials: M
authors.lastname: Shoap
authors.forename: Mary
authors.initials: M
authors.lastname: Gotwald
authors.forename: John
authors.initials: J
authors.lastname: Trail
authors.forename: Ana L
authors.initials: AL
authors.lastname: Gomez
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Volek
authors.forename: Cristina
authors.initials: C
authors.lastname: Cortis
authors.forename: Brett A
authors.initials: BA
authors.lastname: Comstock
authors.forename: David R
authors.initials: DR
authors.lastname: Hooper
authors.forename: Tunde K
authors.initials: TK
authors.lastname: Szivak
authors.forename: David P
authors.initials: DP
authors.lastname: Looney
authors.forename: William H
authors.initials: WH
authors.lastname: DuPont
authors.forename: Danielle M
authors.initials: DM
authors.lastname: McDermott
authors.forename: Michael C
authors.initials: MC
authors.lastname: Gaudiose
authors.forename: William J
authors.initials: WJ
authors.lastname: Kraemer
mesh_terms: D001823:Body Composition; D015992:Body Mass Index; D001835:Body Weight; D002648:Child; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D010807:Physical Endurance / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D012727:Sex Characteristics; D046468:Sexual Development / Q000502:physiology*