Analysis of the physical fitness development trajectory of children and adolescents with severe intellectual disabilities in orphanages: A three-year longitudinal follow-up study

PURPOSE: This study aimed to systematically characterise the development trajectory of physical fitness in children (7-12 years) and adolescents (13-18 years) with severe intellectual disability living in orphanages, based on 12 repeated assessments over three years. METHODS: A total of 132 children and adolescents aged 7-18 years with severe intellectual disabilities from orphanages in four regions of China were selected. Longitudinal trends in fitness indicators were assessed using generalised estimating equations (GEE). RESULTS: At baseline, the cohort included 93 boys (70.5%) and 39 girls (29.5%), comprising 57 children aged 7-12 years (9.29 ± 1.81 years) and 75 adolescents aged 13-18 years (14.80 ± 1.65 years). Most participants were normal weight (81.8%), with 3.1% overweight/obese and 15.1% underweight/severely thin at baseline. Baseline analyses indicated sex differences in several strength-related indicators (P ≤ 0.008), whereas BMI did not differ by sex (P = 0.21). Longitudinal analyses showed that (1) The BMI of children and adolescents with severe intellectual disabilities is on the rise (P < 0.01); (2) gains in strength and balance were more pronounced and developmentally sensitive during childhood; (3) in adolescents, core strength and balance displayed an atypical pattern with a mid-period decline followed by gradual recovery, suggesting potential neuromuscular coordination challenges; (4) overall physical fitness improved over time in children and adolescents (7-18 years) (P < 0.001), but remained lower than typically developing reference levels, indicating an atypical developmental trajectory. CONCLUSION: Physical fitness development in children and adolescents with severe intellectual disability is age-specific. Strength and balance training should be prioritised in childhood, whereas weight monitoring and core stability interventions should be strengthened in adolescence. Orphanage-based programmes should integrate motor skill development with metabolic risk management to address the dual challenges of developmental delay and obesity.