Background and aims: In the recent decade, obesity and physical inactivity due to internet addiction among children and adolescent, has become a global concern. This study investigated the effects of 2 and weeks of the Whole-Body Functional Training (WB-FT) on central obesity indices include abdominal volume index (AVI), Conicity Index (CI), body adiposity index (BAI), Waist-to-Height Ratio (WHtR), A Body Shape Index (ABSI) and on exercise capacity indices such as peak oxygen consumption (VO2Peak), maximum heart rate (HRmax), myocardial oxygen consumption (MVO2), myocardial oxygen consumption recovery (MVO2R), and heart rate recovery (HRR) in internet-addicted adolescents in Saqqez, Iran.

Methods: This quasi-experimental study with a pre-test and post-test design involved 80 adolescents (40 boys and 40 girls). Participants were randomly divided into four exercise and control groups, and the intervention was implemented for 2 and 4 weeks. Body composition indices and cardiorespiratory endurance were assessed before and after the intervention using standard protocols.

Results: 4 weeks of WB-FT improved WHtR, BAI, and CI in boys (P<0.05). Additionally, even 2 weeks of WB-FT resulted in significant improvements in VO2Peak in both sexes compared to control groups(P<0.05). However, changes in central obesity indices were not significant in girls.

Conclusions: Unlike VO2Peak, the improvement in body composition resulting from WB-FT training, especially in internet addicted girls, requires a longer intervention period (4 weeks). These findings demonstrate the importance of even short-term training interventions of up to 4 weeks in reducing the complications of inactivity and obesity in adolescents.