Data-driven modelling of low-dimensional dynamical structures underlying complex full-body human movement

TL;DR

This study employs neural ordinary differential equations to model complex full-body human movements as low-dimensional dynamical systems, demonstrating accurate predictions and the potential to extend dynamical systems analysis to ecologically valid movements.

Contribution

It introduces a novel application of NODEs to model non-cyclic, complex human movements, advancing the dynamical systems approach beyond simple or cyclic motions.

Findings

Accurately predicted complex pitching motion (R^2 > 0.45)

Half of the variance in late movement phases explained by initial 8%

Demonstrated potential to extend DSA to complex, real-world movements

Abstract

One of the central challenges in the study of human motor control and learning is the degrees-of-freedom problem. Although the dynamical systems approach (DSA) has provided valuable insights into addressing this issue, its application has largely been confined to cyclic or simplified motor movements. To overcome this limitation, the present study employs neural ordinary differential equations (NODEs) to model the time evolution of non-cyclic full-body movements as a low-dimensional latent dynamical system. Given the temporal complexity full-body kinematic chains, baseball pitching was selected as a representative target movement to examine whether DSA could be extended to more complex, ecologically valid human movements. Results of the verification experiment demonstrated that the time evolution of a complex pitching motion could be accurately predicted (R^2 > 0.45) using the NODE-based dynamical model. Notably, approximately 50% of the variance in the latter half of the pitching motion was explained using only the initial ~8% of the temporal sequence, underscoring how subsequent movement evolves from initial conditions according to ODE-defined dynamics in latent space. These findings indicate the potential to extend the DSA to more complex and ecologically valid forms of human movement.