# Let's rock -Classification of Balance Recovery Steps in the Wild: Application to Punk Rock Concerts

Thomas Chatagnon, Anne-Hélène Olivier, Ludovic Hoyet, Julien Pettré, Charles Pontonnier

► To cite this version:

Thomas Chatagnon, Anne-Hélène Olivier, Ludovic Hoyet, Julien Pettré, Charles Pontonnier. Let's rock -Classification of Balance Recovery Steps in the Wild: Application to Punk Rock Concerts. ISPGR 2025 - International Society of Posture and Gait Research, Jun 2025, Maastricht, Netherlands. pp.1-1, 2025. [https://doi.org/10.4994/ispgr.2025-1](https://doi.org/10.4994/ispgr.2025-1).

HAL Id: hal-04994003

https://inria.hal.science/hal-04994003v1

Submitted on 17 Mar 2025

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# Let's rock - Classification of Balance Recovery Steps in the Wild: Application to Punk Rock Concerts

Thomas Chatagnon¹, Anne-Hélène Olivier², Ludovic Hoyet², Julien Pettré², and Charles Pontonnier²

¹IAS-7: Civil Safety Research, Forschungszentrum Juelich, Juelich, Germany

²Univ Rennes, Inria, CNRS, IRISA, M2S, France

## Background and Aim

Dense crowds are challenging environments in which individuals may experience external perturbations from multiple directions. These interactions may result in loss of standing balance, triggering recovery strategies. Since the risk of falling in dense crowds is a key element in crowd studies, understanding the motion induced by contacts and pushes in such situations is crucial. In this study, we present a novel classification method to label stepping recovery strategies following external perturbation. This approach does not require information regarding the perturbations, hence allowed us to investigate recovery strategies in an ecological crowded environment involving physical interactions: punk rock concert crowds.

## Methods

This work includes two main components. We first developed a novel *Unified* method to label recovery strategies. Unlike previous methods, this approach enables the classification of recovery steps without prior information about the perturbation itself. This method was first tested on a push-recovery dataset including more than 1400 recording of 21 healthy young adults undergoing perturbations from 5 different directions. We then propose an experimental protocol that allowed the recording of recovery strategies in a crowded environment using an IMU-based motion capture system. We used this protocol to create a proof of concept in which 147 recovery strategies of three participants were recorded during punk rock concerts. This proof of concept enables the comparison of recovery strategies recorded in real-world settings with observations collected during previous laboratory experiments.

## Results

Several results emerged from this study. First, despite the inherent polarization of the concert crowd, perturbations were estimated to originate from all possible directions. The majority of recovery strategies used by participants were similar to those observed in laboratory experiments under comparable conditions. However, the characteristics of recovery steps appear to be different compared to laboratory experiments. Participants in the concert crowd tend to use smaller and faster recovery steps compared to participants in laboratory experiments for comparable perturbations.

## Conclusions

This study presents a novel classification method for labeling recovery steps following external perturbation. This method does not rely on prior information about perturbations, enabling investigations in real-world settings. We then combined this approach with a novel experimental paradigm to create a proof of concept within a crowded environment. This enabled us to compare field observations to previous laboratory experiments and to suggest that recovery strategies in concert crowds are comparable to what was observed in laboratory experiments, despite differences in the characteristics of the recovery steps.