Muscle Function and Bone Strength in Children and Adolescents with Tall Stature

Introduction: Muscle functions are dependent on age, weight and height. The question of how the muscle–bone unit is adapted for tall stature is yet to be elucidated. The aim of this study was to evaluate muscle functions and markers of bone strength in children and adolescents with tall stature. Methods: A total of 98 children and adolescents participated in the study and were divided into two groups: the tall stature (TS) group included 63 non-trained participants (mean age 13.4±3.2 years, height Z-score 3.0±0.7); the basketball players (BP) group included 35 actively training basketball players (mean age 16.8±1.9 years, height Z-score 2.7±0.4). Dynamic muscle functions—relative muscle power (Pmax/mass) and force (Fmax/body weight)—were assessed using jumping mechanography and compared between groups. Parameters of bone strength were assessed in the TS group using pQCT and DXA. Results: Z-scores of Pmax/mass and Fmax/body weight were significantly decreased in the TS group compared with age- and sex-specific normative values (mean −1.28±1.15; p<0.001, and −1.10±1.06; p<0.001), but increased in the BP group (mean 0.99±1.15; p<0.001 and 0.64±1.42; p<0.05). Children in the TS group had decreased cortical bone mineral density (BMD) and cortical thickness (mean Z-scores −0.78±1.0 and −0.57±1.12; p<0.001 for both). Trabecular BMD was normal (mean Z-score 0.31±1.46; p=0.14) and the Stress–Strain Index (SSI) was increased (1.93±0.96; p<0.001). Z-scores of lumbar spine BMD and whole-body bone mineral content (BMC) measured by DXA were increased (0.99±1.22; p<0.001; 1.81±1.04; p<0.001), whereas whole-body BMD was normal (0.19±1.16; p=0.24). Conclusion: Dynamic muscle functions relative to body mass are decreased in healthy untrained individuals with tall stature, unlike trained individuals with tall stature. Reduced mechanical stimulation may contribute to decreased cortical BMD and thickness at the tibia in this group.