Agenda

PhD defense Qi Gan: Sports Motion Analysis

Friday 12 September 2025, at 14.00 (Paris time) at Télécom Paris

Télécom Paris, 19 place Marguerite Perey F-91120 Palaiseau [getting there], amphi 6 and in videoconferencing

Full title: Sports Motion Analysis: From Competition Videos to Data-Driven Interpretations

Jury

  • Saïd LADJAL, Professor, Télécom Paris, France (President)
  • Sotiris MANITSARIS, Deputy Director of the Robotics Center, Mines Paris – PSL, France (Reviewer)
  • François RIOULT, Associate Professor, University of Caen – CNRS UMR6072 GREYC, France (Reviewer)
  • Rikke GADE, Associate Professor, Aalborg University, Denmark (Examiner)
  • Germain FORESTIER, Professor, Université de Haute Alsace, France (Examiner)
  • Stephan CLEMENÇON, Professor, Télécom Paris, France (Thesis Director)
  • Mounîm A. El YACOUBI, Professor, Télécom SudParis, France (Thesis Co-supervisor)

Abstract

Understanding human movement is fundamental to human-centered activities. In this study, we focus on a specific category: sports motions. Our investigation begins by addressing the challenges of collecting sports motion data from online videos, which include estimating human poses from low-quality frames and reconstructing global 3D poses from single-view, moving-camera footage.

We then pursue two complementary approaches...

… to analyze sports motions. The first involves biomechanical feature analysis. We adopt a classical pipeline that trains a machine learning model and interprets it using explainable AI techniques. A quantile random forest regressor is employed to emphasize top performance, and the model is interpreted using SHapley Additive exPlanations (SHAP), along with Partial Dependence Plots (PDPs) and Individual Conditional Expectation (ICE) plots. The analysis yields insights consistent with prior literature. However, this approach is limited in its ability to capture interactions between features, which are often critical. To address this, we introduce a novel method to estimate functional interactions, which not only quantifies interaction strength but also characterizes how and where these interactions occur. The second approach focuses on analyzing pose sequences, with an emphasis on interpreting black-box time-series models. We generate counterfactual explanations using a sparse autoencoder-based framework. Experimental results demonstrate that our method produces explanations that are both faithful and robust.