Lower Limb Joint Reaction Forces and Moments Calculations for a “Dabke Jump”: Application of 3D Inverse Dynamics Technique

Abstract

The study involves applying the inverse dynamics to calculate the 3-dimensional (3D) reaction forces and moments at the lower limbs namely: hip, knee, and ankle joints. The study is specific to performing the Lebanese folkloric dance known as the “Dabke jump”. The aim is to compare the impact forces generated at the three joints. Also envisioned is to contrast the forces generated for a male (63 Kg) and a female (50.4 kg) dancer (barefoot and while she wears 8.5 cm high heels). The experimental part of the study consists of measuring position data of the right lower limb of the participant when performing the jump. All at once, the reaction forces generated at the impact are synchronously measured. The position data are obtained using the OptiTrack™ motion capture system. The ground reaction forces are measured using the AMTI force plate. Using kinematics analysis in conjunction with inverse dynamics, the filtered and fitted experimental data are then imported into MATLAB® to obtain a table containing all the internal forces and moments at each joint (ankle, knee, and hip joints) as function of time. Next, the results are plotted and compared. Force and moment data are analyzed using R Project for statistical computing software. The boxplot technique is used to identify the presence of outliers. Using both MannWhitney and Krustkal Wallis tests, all joint reaction forces and moments in three dimensions are analyzed, at different time intervals to instantaneously identify the prominent effect on each joint. It is found that the largest impact force is generated at the ankle joint for both subjects. For the male participant, the impact maximum vertical force measured at the ankle is about 2.2 of body weight (BW). For the female participant, a maximum vertical force of 1.84 BW is recorded both barefoot and with heals. The forces and moments obtained for this male individual are larger than those obtained for this female individual. Moreover, for the female participant the vertical forces obtained for all joints when wearing an 8.5 cm high heel are found to be lower than those obtained when she is barefoot. This is most notably recorded at the hip joint where a maximum decrease of 21.2% is observed. This finding suggests that when a dancer performs the “Dabke jump”, wearing an appropriate heel of suitable height will decrease the vertical impact forces on the lower limb joints and decrease the risk of injuries.