# Energy Assessment of the Soldier's Technique for Load-carrying Obstacle Crossing

Aurélien Schuster, Charles Pontonnier, Georges Dumont

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Aurélien Schuster, Charles Pontonnier, Georges Dumont. Energy Assessment of the Soldier's Technique for Load-carrying Obstacle Crossing. ESB 2025 - 30th Congress of the European Society of Biomechanics, Jul 2025, Zürich, Switzerland. pp.1-1. hal-05008537

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Submitted on 27 Mar 2025

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Distributed under a Creative Commons Attribution 4.0 International License
# ENERGY ASSESSMENT OF THE SOLDIER'S TECHNIQUE FOR LOAD-CARRYING OBSTACLE CROSSING

Aurélien Schuster (1,2), Charles Pontonnier (2), Georges Dumont (2)

1. Centre de Recherches des écoles de Saint-Cyr Coëtquidan, France

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

## Introduction

The impact of carrying heavy loads on soldiers' physiology has a great interest in armed forces. However, energy assessment of soldier's mobility mainly focuses on locomotion. Thus, a standardized obstacle course was designed as part of the LEAP (Load Effect Assessment Program, [1]) to study the US Army soldier's equipment with better representation of the mission. However, the results of the literature on this obstacle course are mainly composed of chronometric values, but it would be interesting to quantify the energy expenditure of this type of movement in the framework of load carriage optimization. The aim of this study is to quantify the soldier's mechanical energy and work of an obstacle crossing movement using motion analysis.

## Methods

A volunteer participant (male, 1m77, 85.3kg) completed 10 obstacle crossings (low barrier of 1 meter height) with the same technique (1 or 2 hands and 1 foot simultaneously on the barrier), without load and with a backpack of 11.3kg and 17kg. 45 markers were placed on the body landmarks according to the ISB recommendations and technical markers were placed on the pelvis and torso to reconstruct the markers hidden by the backpack. Reaction forces were measured using force platforms and a force sensor on the obstacle. The position of the center of mass, joint velocities ($\dot{q}$) and joint torques ($\tau$) were then computed by inverse kinematics and inverse dynamics using the biomechanical toolbox CusToM [2]. Mechanical energy [3] and joint work were computed. The net joint work explains the variation of mechanical energy during the movement (Eq. 1) and the absolute joint work is resulting from the soldier's energy expenditure (Eq. 2):

$$ \Delta E_{\text{m, phase}} = \sum_{N_q} \int \tau_i \dot{q}_i dt_{\text{phase}} \quad (1) $$

$$ W_{\text{abs, phase}} = \sum_{N_q} \int |\tau_i \dot{q}_i| dt_{\text{phase}} \quad (2) $$

## Results

Different phases were identified based on the soldier's energy (Fig. 1). The first phase corresponds to a gain in mechanical energy and highlights positive net joint work (Fig. 2). The second phase corresponds to a constant state of mechanical energy, where the net joint work is low compared to the absolute joint work (as for the whole movement). The last phase linked to the loss of mechanical energy highlights negative net joint work.

Furthermore, absolute work increases with the load carried for the gain phase and the whole movement, which is not the case for the constant and loss phases (Fig. 2).

<figure><img src="image_2.png" /><figcaption>Figure 1: Kinetic, potential and mechanical energy (J) of obstacle crossing (no-load condition).</figcaption></figure>

<figure><img src="image_3.png" /><figcaption>Figure 2: Net joint and absolute joint work (J) for each phase and whole movement.</figcaption></figure>

## Discussion

In the present study, absolute and net joint work were considered as the image of muscular work. However, metabolic criteria should be considered to assess the soldiers' energy expenditure. A more in-depth study will be carried out to validate these results, using a larger number of participants and physiological measurements.

## References

1. Mitchell et al, Proceed. Hum. Fac. and Erg., 45:1-10, 2018.

2. Muller et al, JOSS, 4(33), 927, 2020

3. Peyré-Tartaruga et al., Exp. Physio. 106:1897-1908, 2021

## Acknowledgements

The present study was partly funded by the chair of the enhanced soldier in the digital battlefield from the St-Cyr Foundation and supported by French government funding managed by the National Research Agency under the Investments for the Future program (PIA) with the grant ANR-21-ESRE-0030 (CONTINUUM project).

<figure><img src="image_4.png" /></figure>