Effect of the calculation methods on body moment of inertia estimations in individuals of different morphology.

Body segment moments of inertia (MOI) are estimated from data obtained from cadavers or living individuals. Though these methods can be valid for the general population, they usually are limited when applied to special populations (e.g., obese). The effect of two geometric methods, photogrammetry and two new methods, namely, inverse dynamics and angular momentum on the estimations of MOI in individuals of different body mass index (BMI) were compared to gain insight into their relative accuracy. The de Leva (1996) method was chosen as a criterion to determine how these methods behaved. MOI methods were not different in individuals with a normal BMI. On the average, MOI values obtained with inverse dynamics and angular momentum were respectively 13.2% lower for lean participants and 17.9% higher for obese subjects than those obtained from the de Leva method. The average Pearson coefficients of correlation between the MOI values, estimated by the de Leva method, and the other methods was 0.76 (+/-0.31). Since the proposed methods made no assumption on the mass distribution and segments' geometry, they appeared to be more sensitive to body morphology changes to estimate whole body MOI values in lean and obese subjects.