Hip compression force estimation with a comprehensive musculo- skeletal model

(1) In many models muscle force can instantaneously drop to zero or rise to maximal force (e.g. [2]) However, in reality muscular dynamics will prevent such fast transitions in force. (2) Objective functions based on mechanical measures such as muscle force or stress are frequently used (e.g. [3]). However, the validity of these functions is unknown. A recent study posed an energy-related cost function that had a better correspondence with muscle energy consumption than cost functions based on muscle stress [4]. (3) Since the objective function and its boundaries are a function of anatomical parameters, the outcome of a muscle force optimization is highly dependent on such data. Frequently used datasets are either incomplete or constructed by merging of datasets based on different individuals. This might result in possible inaccuracies caused by inter-individual anatomical differences and co-variance between parameters.