# A comparative analysis of whole-body angular momentum during treadmill and overground Walking

Florian Etheve, Jérémie Begue, Margaux Levasseur, Eve Charbonneau, Ophélie Larivière, Teddy Caderby

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Florian Etheve, Jérémie Begue, Margaux Levasseur, Eve Charbonneau, Ophélie Larivière, et al. A comparative analysis of whole-body angular momentum during treadmill and overground Walking. Multidisciplinary Biomechanics Journal, 2025, 50th congress of the Société de Biomécanique, 10.46298/mbj.16191. hal-05191744v2

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# A comparative analysis of whole-body angular momentum during treadmill and overground Walking

Florian Etheve*, Jérémie Begue, Margaux Levasseur, Eve Charbonneau, Ophélie Larivière, Teddy Caderby

IRISSE, Le Tampon, La Réunion

*Corresponding author: florian.etheve@univ-reunion.fr

Received date: 06/04/2025

Accepted date: 27/06/2025

Publication date: 27/10/2025

**Keywords:** walking, balance, treadmill, overground

© 2025 The Authors

Licence CC-BY 4.0

Published by Société de Biomécanique

## 1. Introduction

Whole-body angular momentum ($H$) is a mechanical quantity that characterizes the rotational behavior of the whole body. It is defined as the sum of angular momenta of all body segments relative to the body's center of mass (CoM). This parameter has been used to investigate balance maintenance during various motor tasks, including walking. Notably, it has been highlighted that $H$ is tightly controlled by the central nervous system, i.e., $H$ is kept small during normal walking conditions (Herr & Popovic, 2008). However, when balance is challenged by external disturbances, an increase in $H$ (has been observed (Martelli et al., 2013)).

Treadmill walking is commonly used for gait assessments and training due to its controlled environment, but it differs biomechanically from overground walking. In comparison with overground walking, treadmill walking increases cadence, and, conversely, decreases stride length and step length (Vickery-Howe et al., 2023). These spatiotemporal alterations are accompanied by changes in ground reaction forces (GRF) and joint kinetics. Specifically, peak ground reaction forces, knee extension moments, and ankle dorsiflexion moments are lower during treadmill walking, whereas hip extension moments tend to be higher (Vickery-Howe et al., 2023). These findings suggest that treadmill walking may influence both foot placement and force generation, which could, in turn, affect control of $H$ (Pijnappels et al., 2004).

The aim of this study was to compare whole-body angular momentum ($H$) between treadmill and overground walking. We hypothesize that $H$ differs between treadmill and overground walking due to biomechanical adaptations imposed by the treadmill environment.

## 2. Methods

### 2.1 Population and experimental procedures

Eight healthy young adults (23 ± 3 years; 5 males) participated after providing informed consent. After a 10-min walking familiarization session on an instrumented dual-belt treadmill (Bertec Corporation, USA), the preferred speed was determined via incremental and decremental protocols on the treadmill. Then, participants completed ten walking trials at their preferred speed on a 7 m walkway and a one-minute treadmill trial, presented in a randomized order. Overground walking speed was monitored using photoelectric cells to ensure consistency with the treadmill speed. Forty-nine retroreflective markers were placed bilaterally. Kinematics were recorded at 100 Hz (Vicon: overground; Qualisys: treadmill).

### 2.2 Data processing and analysis

Kinematic data were filtered using a zero-lag, fourth-order Butterworth filter (10 Hz). The inverse kinematics problem was solved using Biorbd, and $H$ expressed at the CoM was calculated as:
$$ \vec{H} = \sum_{i}^{n} [\vec{r}_{i} \times \mathbf{m}_{i} \vec{v}_{i} + I_{i} \vec{\omega}_{i}] $$

where $\vec{r}_i$ is the position vector of the CoM of segment i relative to the whole-body CoM, $\vec{v}_i$ is the linear velocity vector of segment i relative to the velocity vector of the whole-body CoM, $\mathbf{m}_i$ and $I_i$ are the mass and inertia tensor of segment i, respectively, and $\vec{\omega}_i$ is the angular velocity of segment i around its own CoM. H was normalized by $h \cdot m \sqrt{g \cdot h}$, where h and m are the participant's height and mass, respectively, and g = 9.81 m·s⁻². The peak-to-peak range of H (difference between maximum and minimum values of H) and spatiotemporal parameters (cadence, step length, step width and stride length) were calculated for each cycle and then averaged across 10 cycles.

## 2.3 Statistical analysis

Shapiro-Wilk and Levene's tests assessed normality and variance homogeneity. For normally distributed variables, a paired t-test was used; otherwise, a Wilcoxon signed-rank test was applied. Statistical significance was set at $p < 0.05$.

## 3. Results and discussion

Statistical analyses revealed significant differences in the H ranges between treadmill and overground walking conditions (Fig. 1). A smaller range of H was observed during treadmill walking compared with overground walking, in both the sagittal plane and the transversal plane. No significant difference was found between treadmill and overground walking conditions in the frontal plane.

<table><caption>**Table 1:** Spatiotemporal gait parameters for treadmill and overground walking. \* p < .05, \*\* p < .01, \*\*\* p < .001.</caption><thead><tr><th></th><th>Treadmill</th><th>Overground</th></tr></thead><tbody><tr><td>Cadence (step/min)</td><td>106.03 ± 8.07</td><td>97.45 ± 7.50***</td></tr><tr><td>Step length (cm)</td><td>43.36 ± 4.68</td><td>62.44 ± 4.45***</td></tr><tr><td>Step width (cm)</td><td>11.92 ± 2.59</td><td>10.56 ± 1.87</td></tr><tr><td>Stride length (cm)</td><td>120.35 ± 20.54</td><td>140.70 ± 11.62**</td></tr></tbody></table>

All spatiotemporal gait parameters are presented in Table 1. Compared to overground walking, treadmill walking resulted in shorter step length and stride length, as well as increased cadence.

<figure><img src="image_2.png" /><figcaption>**Figure 1:** Mean and SD values of Hrange in the frontal, sagittal and transversal planes during treadmill (blue) and overground (red) conditions. \* p < .05, \*\* p < .01, \*\*\* p < .001.</figcaption></figure>

The results indicate that treadmill walking results in smaller variations in H in the sagittal and transversal planes compared to overground walking. This reduced range of H may reflect lower demands for balance control, as larger variations in H are typically observed under challenging balance conditions (Martelli et al., 2013). This difference may be explained by treadmill walking does not replicate ecological walking conditions. Consequently, the lower range of H observed during treadmill walking may reflect a more cautious strategy adopted by individuals to enhance stability. This hypothesis is supported by spatiotemporal gait changes observed in our study, such as increased cadence and decreased step length, which are commonly considered stability-enhancing strategies (Hak et al., 2013).

In the frontal plane, the lack of differences between the two walking conditions might be explained by the tendency for a wider step width during treadmill walking, likely promoted by the dual-belt design.

## 4. Conclusions

Compared to overground walking at matched speed, treadmill walking reduced H range in the sagittal and transversal planes, with no change in the frontal plane. These findings may be valuable when designing protocols for gait assessment or retraining.

### Conflict of interest statement

The authors report no conflict of interest.
## Contributor Roles

FE: Conceptualization, Methodology, Data curation, Formal analysis, Software, Writing original draft; JB: Conceptualization, Methodology, Writing-review & editing; ML: Methodology, Investigation, Formal analysis, Writing-review & editing; EC: Methodology, Software, Writing-review & editing; OL: Methodology, Software, Writing-review & editing; TC: Conceptualization, Methodology, Funding acquisition, Supervision, Writing-review & editing.

## Funding

Our work was supported by a Regional Research Grant from the Réunion Region (grant #301410) and the European Regional Development Fund. This research is part of the e-WALKING project (ANR-22-CE19-0009), funded by the French National Research Agency.

## Data, software, code availability

The author declares that no open-source data, software, or code is available for this study.

## References

Hak, L., Houdijk, H., Beek, P. J., & Van Dieën, J. H. (2013). Steps to take to enhance gait stability: The effect of stride frequency, stride length, and walking speed on local dynamic stability and margins of stability. *PLoS ONE*, 8(12), e82842. https://doi.org/10.1371/journal.pone.0082842

Herr, H., & Popovic, M. (2008). Angular momentum in human walking. *Journal of Experimental Biology*, 211(4), 467-481. https://doi.org/10.1242/jeb.008573

Martelli, D., Monaco, V., Luciani, L. B., & Micera, S. (2013). Angular momentum during unexpected multidirectional perturbations delivered while walking. *IEEE Transactions on Biomedical Engineering*, 60(7), 1785-1795. https://doi.org/10.1109/TBME.2013.2241434

Pijnappels, M., Bobbert, M. F., & Van Dieën, J. H. (2004). Contribution of the support limb in control of angular momentum after tripping. *Journal of Biomechanics*, 37(12), 1811-1818. https://doi.org/10.1016/j.jbiomech.2004.02.038

Vickery-Howe, D. M., Bonanno, D. R., Dascombe, B. J., Drain, J. R., Clarke, A. C., Hoolihan, B., Willy, R. W., & Middleton, K. J. (2023). Physiological, perceptual, and biomechanical differences between

treadmill and overground walking in healthy adults: A systematic review and meta-analysis. *Journal of Sports Sciences*, 41(23), 2088-2120. https://doi.org/10.1080/02640414.2024.2312481