Author(s): ROGGIO, F., POLITI, M., MUSUMECI, G., Institution: UNIVERSITY OF CATANIA, Country: ITALY, Abstract-ID: 925

INTRODUCTION:
Gait analysis is commonly performed in controlled settings such as laboratories or treadmills, often assuming that these conditions reflect natural walking behavior. However, locomotion is strongly context-dependent, as environmental constraints can alter both spatiotemporal parameters and neuromuscular control. Understanding how different walking environments influence gait outcomes is therefore crucial for the correct interpretation of gait analysis results. This study investigated how laboratory, treadmill, and real-world walking environments modulate spatiotemporal parameters and neuromuscular control strategies.

METHODS:
Fifty-three healthy adults performed three walking trials in randomized order: laboratory overground, outdoor, and treadmill walking, with five minutes of rest between trials. Gait analysis was recorded using the inertial measurement unit BTS G-Walk® system, while surface electromyography was collected using the FREEEMG system (BTS Bioengineering, Italy). EMG electrodes were placed bilaterally on tibialis anterior, medial gastrocnemius, semitendinosus, and rectus femoris muscles. A familiarization period was completed before treadmill walking. EMG signals were peak-normalized, and a total muscle activation cost was computed as the sum of squared normalized activations. Linear mixed-effects models were used to compare conditions and to assess condition-by-speed interactions.

RESULTS:
Spatiotemporal parameters differed significantly across walking conditions (all p < 0.05). Total muscle activation cost showed a significant main effect of condition when adjusting for walking speed (p = 0.001), with higher values during outdoor compared to laboratory walking (mean difference = 0.29, p = 0.001). A significant condition × speed interaction was observed (p = 0.031), indicating a context-dependent relationship between walking speed and neuromuscular demand. Slope analyses indicated that muscle activation cost increased with speed during outdoor walking (β = 0.67), showed a weaker, non-significant association during laboratory walking (β = 0.39), and was not associated with speed during treadmill walking (β = −0.19). The increase in activation cost with speed was significantly greater outdoors than on the treadmill (p = 0.038).

CONCLUSION:
The environment in which gait is assessed plays a critical role in shaping both spatiotemporal outcomes and neuromuscular strategies. Laboratory, outdoor, and treadmill walking cannot be considered interchangeable contexts, as each condition emphasizes different dimensions of gait behavior. These findings highlight the importance of contextualizing gait analysis results and caution against direct comparisons across environments without considering their specific biomechanical and neuromuscular constraints.

Acknowledgments
The work is funded by the Italian Ministry of University and Research (MUR) as part of the PRO-BEN - UNIST-HEALTH Project.