Model of joint displacement using sigmoid function. Experimental   approach for planar pointing task and squat jump
  Using an experimental optimization approach, this study investigated whether two human movements, pointing tasks and squat-jumps, could be modelled with a reduced set of kinematic parameters. Three sigmoid models were proposed to model the evolution of joint angles. The models parameters were optimized to fit the 2D position of the joints obtained from 304 pointing tasks and 120 squat-jumps. The models were accurate for both movements. This study provides a new framework to model planar movements with a small number of meaningful kinematic parameters, allowing a continuous description of both kinematics and kinetics. Further researches should investigate the implication of the control parameters in relation to motor control and validate this approach for three dimensional movements. 
Thomas Creveaux, J\'er\^ome Bastien, Cl\'ement Villars, and Pierre   Legreneur
q-bio.QM physics.bio-ph