Explaining automated gender classification of human gait

TL;DR

This study applies Layer-wise Relevance Propagation to a CNN model to explain which gait features influence automated gender classification, improving interpretability of ML predictions in gait analysis.

Contribution

It demonstrates how LRP can reveal relevant gait features for gender classification, enhancing explainability of ML models in biomechanics.

Findings

CNN achieved 83.3% accuracy in gender classification

LRP identified gait patterns consistent with literature

Explainability methods clarified model decision basis

Abstract

State-of-the-art machine learning (ML) models are highly effective in classifying gait analysis data, however, they lack in providing explanations for their predictions. This "black-box" characteristic makes it impossible to understand on which input patterns, ML models base their predictions. The present study investigates whether Explainable Artificial Intelligence methods, i.e., Layer-wise Relevance Propagation (LRP), can be useful to enhance the explainability of ML predictions in gait classification. The research question was: Which input patterns are most relevant for an automated gender classification model and do they correspond to characteristics identified in the literature? We utilized a subset of the GAITREC dataset containing five bilateral ground reaction force (GRF) recordings per person during barefoot walking of 62 healthy participants: 34 females and 28 males. Each input signal (right and left side) was min-max normalized before concatenation and fed into a multi-layer Convolutional Neural Network (CNN). The classification accuracy was obtained over a stratified ten-fold cross-validation. To identify gender-specific patterns, the input relevance scores were derived using LRP. The mean classification accuracy of the CNN with 83.3% showed a clear superiority over the zero-rule baseline of 54.8%.