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Current Opinion
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Proactive control to navigate our daily environments
Department of Rehabilitation, Faculty of Medicine, Université Laval, Québec, Canada.
Centre for Interdisciplinary Research in Rehabilitation and Social Integration, CIUSSS-CN, IRDPQ, Canada.
School of Physical and Occupational Therapy, McGill University, Canada.
Feil and Oberfeld Research Centre, Jewish Rehabilitation Hospital CISSS Laval Site of Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal
(CRIR), Canada.
Univ Rennes, INRIA, CNRS, IRISA, M2S, Rennes, France.
Department of Kinesiology & Physical Education, Wilfrid Laurier University, Waterloo, ON, Canada.
Human Movement Research Laboratory (MOVI-LAB), Department of Physical Education, São Paulo State University (Unesp), Bauru, SP, Brazil.
Correspondence to: Bradford J. McFadyen. Centre for Interdisciplinary Research in Rehabilitation and Social Integration, CIUSSS-CN, IRDPQ, Canada.
ALAs Anticipatory Locomotor
Received 20 10 2022
Accepted 30 11 2022
Published 15 12 2022
Safely navigating our environment is crucial to daily living, but the study of locomotor navigational control in relation to the
complex interaction of personal and environmental factors is still in its infancy. Work to now has proposed different proactive
control variables for collision avoidance based on visual information. Such control has more recently been shown to be specific
to personal (e.g., age, neurological diseases) and environmental (e.g., obstacle type) characteristics. Continued study of the
complex person-environment interaction is required along with continued theorization on combined proactive and reactive control
KEYWORDS: Locomotion | Navigation | Vision | Anticipatory Control | Obstacle Avoidance | Cluttered Environment
The interest in understanding how humans walk dates back centuries while more
formal measurements using technology arrived later in the 19
century. The 20
saw an exponential growth in locomotor studies, especially with the advancement in kinetic
and motion capture technology, and from the latter part of that century to now, the advent of
virtual reality has provided ways to control environmental factors. In all this, the study of how
locomotion is adapted to the environment is fairly recent despite the fact that navigating and
adapting for the environment makes up a large part of our daily locomotor activity. Locomotor
navigation is performed best when the physical characteristics of the environment can be
anticipated. Such Anticipatory Locomotor Adjustments (ALAs) rely vitally on visual
information to both accommodate environmental facilitators (e.g., passing through a door
aperture) and avoid environmental obstacles (e.g., circumventing objects or another
To accommodate an aperture crossing requires accurate visuo-motor coupling.
Such crossing behaviours are dependent on the physical characteristics of the aperture (i.e.,
static, closing, people, poles, etc.) and are scaled either to one’s body size or action
capabilities. For instance, people use body scaled information when passing through static
apertures, and apertures smaller than about 1.3 times one’s shoulder width become a critical
point to elicit shoulder rotation
. Conversely, when apertures are dynamically changing size,
individuals tend to adjust their walking speed when they are approximately 2 m from the
aperture, although this distance can decrease when the individual’s knowledge of their
action capabilities is affected (e.g., fatigue)
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Such proactive control for locomotor navigation is also crucial for circumventing
objects. Circumvention involves first an ‘en bloc’ control of head and trunk rotation thought
to preserve visual attention on the obstruction
. This then initiates a two-phase trajectory
deviation beginning about 4.5m from the obstacle with a more a pronounced deviation within
2m that allows the preservation of an elliptical safety zone, or personal space, around the
. Like for aperture crossing noted above, these control variables that define ALAs for
single object circumvention are also adapted for different contexts related to personal and
environmental factors.
Yet, daily environmental contexts can involve more complex navigational situations
such as walking through crowds. Work involving crowd simulation
can be used to
understand if pedestrians use multiple strategies to navigate in a densely populated
environment that includes both path planning and local collision avoidance. Analysis of
pedestrians’ trajectories and gaze behaviour in crowds has shown that virtual pedestrians
with a perceived risk of collision are fixated 2.3 times more
. Within a crowd context, local
collision avoidance control needs to regulate a proxemics that both seeks apertures and
maintains social distancing, depending on the crowd properties (e.g., density, geometry).
The relative weighting between path planning and obstacle avoidance could be a dynamic
process which evolves depending on the environmental context.
The navigation tasks noted above are affected by changes in one’s sensorimotor
and cognitive capacities whether due to normal ageing or to more important changes from
impairments. For example, when circumventing obstacles mimicking diagonally approaching
pedestrians, people with stroke presented with approximately 25% larger obstacle
clearances and those with more functional limitations preferentially passed behind as
opposed to in front of the obstacles
. These alterations in collision avoidance strategies and
the ensuing number of collisions with surrounding obstacles or pedestrians become even
more pronounced in the presence of visual-perceptual disorders such as post-stroke
hemineglect as well as with the addition of a simultaneous cognitive task while walking (e.g.,
dual tasking)
. Similarly, it has also been shown that people with Parkinson’s Disease delay
their gaze fixations towards an obstacle to be circumvented by about 1s as compared to
neurologically healthy individuals, and this delay is increased when dual-tasking (about 2s).
This population also move their head 17.5% more than their trunk while preparing for
obstacle circumvention
. These are only brief examples of impaired locomotor navigation
ability. More research involving populations from mild to severe impairments in cognitive and
physical functioning is required in order to transfer evidence and better intervene on daily
mobility and social participation. The natural combination of cognitive, social, and motor
demands of locomotor navigation can be exploited to assess mobility within more ecological
contexts at various stages following impairments.
Overall, much more research is needed to better understand the complex human-
environment interaction underlying locomotor navigation. While it is of our opinion that the
control of ALAs is planned and predominantly proactive in nature, there is other research
suggesting that locomotor navigation is controlled more on-line
. Further modeling and
experimental studies exploring the trade-off between reactive and anticipatory factors are
needed to not only advance knowledge of locomotor navigation control but to continue to
develop more effective assessment and training tools for improving mobility in different
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Citation:!McFadyen BJ, Lamontagne A, Olivier A-H, Pettré J, Cinelli M, Barbieri FA. (2022). Proactive control to
navigate our daily environments. Brazilian Journal of Motor Behavior, 16(5):315-318.
Editor-in-chief: Dr Fabio Augusto Barbieri - São Paulo State University (UNESP), Bauru, SP, Brazil. !
Associate editors: Dr José Angelo Barela - São Paulo State University (UNESP), Rio Claro, SP, Brazil; Dr Natalia
Madalena Rinaldi - Federal University of Espírito Santo (UFES), Vitória, ES, Brazil; Dr Renato de Moraes University
of São Paulo (USP), Ribeirão Preto, SP, Brazil.
Section editor (Current Opinion): Dr Luis Augusto Teixeira - University of São Paulo (USP), São Paulo, SP, Brazil;
Dr Tibor Hortobágyi - University of Groningen, The Netherlands; Dr Renato de Moraes - University of São Paulo
(USP), Ribeirão Preto, SP, Brazil.
Copyright: © 2022 McFadyen, Lamontagne, Olivier, Pettré, Cinelli and Barbieri and BJMB. This is an open-access
article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives 4.0
International License which permits unrestricted use, distribution, and reproduction in any medium, provided the
original author and source are credited.
Funding: There was no funding for this study.
Competing interests: The authors have declared that no competing interests exist.