A rationale is presented for examining the relationship between the inertia of a segment and the torque curve for the corresponding joint, during childhood and adolescence. Joint torque impulse was selected as the criterion variable and segment mass, segment moment of in ertia about the transverse joint axis and age selected as predictor variables. The designated segment was the combined head, arms and trunk (HAT) in the reference configuration. Two joints, the hip and the ankle, were selected for torque analysis. The purpose of the study was to examine through visual inspection, intra-individual curves of the relationships. Data were taken from a mixed longitudinal investigation of twelve boys followed over five years for an age range of five to eighteen years. Segment inertias were estimated using the elliptical zone model and joint torques were calculated from cinematographic records of a standing jump for distance using the inverse dynamics approach. The results show an increasing slope for joint torque impulse with age. This is similar to the reported relationship for strength. The relationships between hip torque impulse and the mass and moment of inertia of HAT are essentially rectilinear. This is in contrast with the reported relationships between strength and weight, height and height squared which show an increasing slope. The relationships for the ankle were similar to those for the hip but the curves were more dispersed, possibly due to the more remote linkage between the ankle and the HAT. It is concluded that the relationship between structure and function, when an impulse/momentum rationale is used to select appropriate variables, approaches collinearity.
Jensen, Robert K.
"Developmental Relationships between Body Inertia and Joint Torques,"
5, Article 3.
Available at: http://digitalcommons.wayne.edu/humbiol/vol60/iss5/3