Jumping Mechanography: Reference Centiles in Childhood and Introduction of the Nerve-Muscle Index to Quantify Motor Efficiency.

Jumping mechanography provides robust motor function indicators among children. The study aim was to develop centiles for the single 2-leg jump (S2LJ) in German children and adolescents and to identify differences in children with obesity. Data were collected in 2004-2021 through the German DOrtmund Nutritional and Anthropometric Longitudinally Designed (DONALD) study. All participants (6-18 years, mean age 11.4) performed annually an S2LJ aiming for maximum height on a Ground Reaction Force Platform. LMS (lambda-mu-sigma), including resampling, was used to develop centiles for velocity (v), jump height (h), relative force (F/BW), relative power (P/mass), impulse asymmetry and a new parameter to describe jump efficiency, the Nerve-Muscle Index (NMI), defined as v/(F/BW). Data from 882 children and adolescents were analyzed (3062 measurements, median 3 per individual). In females, F/BW values were higher in younger age but remained constant in adolescence. v, h and P/mass increased in childhood, reaching a plateau in adolescence. In males, v, h and P/mass showed a constant increase and the F/BW remained lower. Children with obesity showed lower F/BW, h, v and the NMI, hence, lower velocity per relative force unit and less efficient jump. The centiles should be used to monitor motor development in childhood. The NMI is a surrogate for motor efficiency.