title: Fitness Effects of 10-Month Frequent Low-Volume Ball Game Training or Interval Running for 8-10-Year-Old School Children.
abstract: We investigated the exercise intensity and fitness effects of frequent school-based low-volume high-intensity training for 10 months in 8-10-year-old children. 239 Danish 3rd-grade school children from four schools were cluster-randomised into a control group (CON,n= 116) or two training groups performing either 5 × 12 min/wk small-sided football plus other ball games (SSG,n= 62) or interval running (IR,n= 61). Whole-body DXA scans, flamingo balance, standing long-jump, 20 m sprint, and Yo-Yo IR1 children's tests (YYIR1C) were performed before and after the intervention. Mean running velocity was higher (p< 0.05) in SSG than in IR (0.88 ± 0.14 versus 0.63 ± 0.20 m/s), while more time (p< 0.05) was spent in the highest player load zone (>2; 5.6 ± 3.4 versus 3.7 ± 3.4%) and highest HR zone (>90% HRmax; 12.4 ± 8.9 versus 8.4 ± 8.0%) in IR compared to SSG. After 10 months, no significant between-group differences were observed for YYIR1C performance and HR after 2 min of YYIR1C (HRsubmax), but median-split analyses showed that HRsubmaxwas reduced (p< 0.05) in both training groups compared to CON for those with the lowest aerobic fitness (SSG versus CON: 3.2%  HRmax[95% CI: 0.8-5.5]; IR versus CON: 2.6%  HRmax[95% CI: 1.1-5.2]). After 10 months, IR had improved (p< 0.05) 20 m sprint performance (IR versus CON: 154 ms [95% CI: 61-241]). No between-group differences (p> 0.05) were observed for whole-body or leg aBMD, lean mass, postural balance, or jump length. In conclusion, frequent low-volume ball games and interval running can be conducted over a full school year with high intensity rate but has limited positive fitness effects in 8-10-year-old children.
authors.affiliation: Department of Sports Science and Clinical Biomechanics, SDU Sport and Health Sciences Cluster (SHSC), University of Southern Denmark, Odense, Denmark; Department of Nutrition, Exercise and Sports, Copenhagen Centre for Team Sport and Health, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Malte Nejst
authors.identifier: 0000-0002-2600-7126
authors.initials: MN
authors.lastname: Larsen
authors.affiliation: Department of Nutrition, Exercise and Sports, Copenhagen Centre for Team Sport and Health, University of Copenhagen, Copenhagen, Denmark; Health Frederikssund Municipality, Frederikssund, Denmark.
authors.forename: Claus Malta
authors.initials: CM
authors.lastname: Nielsen
authors.affiliation: Department of Sports Science and Clinical Biomechanics, SDU Sport and Health Sciences Cluster (SHSC), University of Southern Denmark, Odense, Denmark; Department of Nutrition, Exercise and Sports, Copenhagen Centre for Team Sport and Health, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Christina
authors.initials: C
authors.lastname: Ørntoft
authors.affiliation: Department of Sports Science and Clinical Biomechanics, SDU Sport and Health Sciences Cluster (SHSC), University of Southern Denmark, Odense, Denmark.
authors.forename: Morten Bredsgaard
authors.initials: MB
authors.lastname: Randers
authors.affiliation: Department of Nutrition, Exercise and Sports, Copenhagen Centre for Team Sport and Health, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Eva Wulff
authors.initials: EW
authors.lastname: Helge
authors.affiliation: Department of Sports Science and Clinical Biomechanics, SDU Sport and Health Sciences Cluster (SHSC), University of Southern Denmark, Odense, Denmark.
authors.forename: Mads
authors.initials: M
authors.lastname: Madsen
authors.affiliation: LIVA Group, Holte, Denmark.
authors.forename: Vibeke
authors.initials: V
authors.lastname: Manniche
authors.affiliation: Team Denmark, Brøndby, Denmark.
authors.forename: Lone
authors.initials: L
authors.lastname: Hansen
authors.affiliation: Department of Cardiology, Herlev-Gentofte University Hospital, Gentofte, Denmark.
authors.forename: Peter Riis
authors.identifier: 0000-0002-9056-535X
authors.initials: PR
authors.lastname: Hansen
authors.affiliation: Department of Nutrition, Exercise and Sports, Copenhagen Centre for Team Sport and Health, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Jens
authors.initials: J
authors.lastname: Bangsbo
authors.affiliation: Department of Sports Science and Clinical Biomechanics, SDU Sport and Health Sciences Cluster (SHSC), University of Southern Denmark, Odense, Denmark; Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK.
authors.forename: Peter
authors.identifier: 0000-0002-1461-9838
authors.initials: P
authors.lastname: Krustrup
mesh_terms: D054874:Athletic Performance / Q000502:physiology*; D002648:Child; D003718:Denmark; D015444:Exercise / Q000502:physiology; D005260:Female; D005538:Football; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D010807:Physical Endurance; D010809:Physical Fitness; D004856:Postural Balance / Q000502:physiology; D012420:Running; D012574:Schools