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 HRsubmax was 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.
Highlights
IntroductionIt is well known that regular physical activity plays a crucial role in preventing a number of diseases challenging modern society [1], and studies show that children who are involved in regular activities in sports clubs have better aerobic fitness and higher bone mineralisation than children who are not members of local clubs [2,3,4]
After 10 months, no significant between-group differences were observed for Yo-Yo IR1 children’s tests (YYIR1C) performance and heart rate (HR) after 2 min of YYIR1C (HRsubmax), but median-split analyses showed that HRsubmax was 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]; interval running (IR) versus CON: 2.6% HRmax [95% CI: 1.1–5.2])
It is well known that regular physical activity plays a crucial role in preventing a number of diseases challenging modern society [1], and studies show that children who are involved in regular activities in sports clubs have better aerobic fitness and higher bone mineralisation than children who are not members of local clubs [2,3,4]
Summary
It is well known that regular physical activity plays a crucial role in preventing a number of diseases challenging modern society [1], and studies show that children who are involved in regular activities in sports clubs have better aerobic fitness and higher bone mineralisation than children who are not members of local clubs [2,3,4]. Most recommendations on physical activity in childhood, to which schoolbased activities contribute, focus on training duration, for example, 60 min/day [5, 6], as recommended by WHO. Recent evidence has shown that intense training is more effective for adults and adolescents in terms of improving musculoskeletal, metabolic, and cardiovascular. In large Danish and international school-based interventions, which have attempted to increase physical activity in children for health improvement, the duration of each physical activity session has often been prolonged, for example, 60 min [13]. If schools are to contribute to children’s health, a timesaving and potentially health-promoting model is desirable. Such a model has not yet been scientifically tested
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