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Brazilian Journal of Motor Behavior
Current Opinion
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Faster walking under muscle fatigability: a strategy to improve stability or a warm-up
effect?
PAULO C. R. SANTOS
1,2,3
| CLAUDINE LAMOTH
4
| NICOLAS VUILLERME
5,6,7
| FABIO A. BARBIERI
2,3
1
Weizmann Institute of Science, Department of Computer Science and Applied Mathematics, Rehovot, Israel.
2
São Paulo State University (UNESP), Human Movement Research Laboratory (MOVI-LAB), Department of Physical Education, Bauru, SP, Brazil.
3
São Paulo State University (UNESP), Graduate Program in Movement Sciences, Bauru, SP, Brazil.
4
University of Groningen, University Medical Center Groningen, Department of Human Movement Sciences, Groningen, The Netherlands.
5
University of Grenoble Alpes, AGEIS, Grenoble, France.
6
Institut Universitaire de France, Paris, France.
7
LabCom Telecom4Health, University of Grenoble Alpes and Orange Labs, Grenoble, France.
Correspondence to:!Paulo Cezar Rocha dos Santos
email: paulocezarr@hotmail.com
https://doi.org/10.20338/bjmb.v15i3.241
PUBLICATION DATA
Received 06 04 2021
Accepted 16 04 2021
Published 01 09 2021
INTRODUCTION
Conceptually, fatigability as a model is biologically relevant to explore gait-related
adaptabilities since fatigability depletes the internal resources available
1,2
and impacts
peripherical and central mechanisms involved in muscle contraction
1
and control of
movements such as gait.
3
Although the term “fatigue” is ubiquitous in sports and, more
recently in healthy aging, the scope of fatigue usage and its effects on gait are still
inconclusive. A potential reason for that is the widespread use of different fatigue
terminologies which complicates translating fatigue to human performance.
1
A taxonomy
was proposed to accommodate the scope of fatigue for different contexts. The taxonomy
conceptualizes fatigue as a trait level - fatigue experienced/reported during the preceding
several days, normally ascribed to diseases or hospitalization - or a state – as a result of
the continuous interaction between performance (a decline in an objective measure of
performance) and perceived fatigability (changes in the self-reported fatigue sensations
associated with the performance).
Regarding the fatigue state, several studies are experimentally inducing fatigability
to examine gait-related adaptability. Normally, such studies design sustained physical or
muscle effort protocols and measure fatigability by a decrease in the level of performance
and/or increase in the perceived exertion. Therefore, it is reasonable to experimentally
induce fatigability to safely examine how humans can adapt their functional tasks to this
internal perturbation,
3
mainly in populations in which fatigue state might be daily
experienced.
Albeit the heterogeneity of endurance or muscle fatiguing protocols, similar
adaptations in gait are observed.
3,4
Among those, unexpected and counterintuitive
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increases in gait velocity (~9%) are consistently observed during overground walking after
different fatiguing protocols in different populations (healthy young and older adults,
Parkinson’s disease).
3–7
Besides, the mechanisms that explain such increases are still
uncertain. Between the attempts to explain such increase, the literature uses two main
theoretical arguments: a potential compensatory strategy to improve stability during
walking;
4,7
and a response of the motor system in increasing the neural drive,
8
similar to
the effects of warm-up activities.
9
Regarding the first argument (the compensatory strategy), the increase in gait
velocity during overground walking after a fatiguing protocol was associated with a more
stable gait pattern,
4,7
because the faster walking velocity is accompanied by longer
stride/step length and shorter step duration.
4,5
Such gait adaptations are attributed to an
improved balance control
9
by seeking more stability in the anterior-posterior direction. For
instance, the extrapolated center of mass, which is velocity-dependent, is anterior to the
base of support, and the increased forward step (length) is a natural response to enhanced
stability by decreasing the magnitude of the margin of stability during walking.
9
Increasing
the step length and decreasing the duration (to increase gait velocity) may be a safe, fast,
effective compensatory strategy to increase the stability and avoid further consequences of
fatigability on gait.
Considering the second argument (warm-up), fatiguing protocols might result in a
preparatory elevation of muscle temperature, alertness, cardiovascular, and hormonal
functions, invoking an increase in gait velocity. Since the metabolic and mechanical
energy-wise minimal effort required during overground walking is low, gait performance
would hardly be limited by fatiguing protocols. Additionally, typical fatigability-related
increases in neural drive
8
might also be an after-effect of warm-up activities that, in some
tasks, result in increased muscle activation amplitude.
9
Thus, the interpretation that
fatigability causes compensatory increase neural drive to maintain the desired
performance, may also be due to warm-up effects, mainly in submaximal tasks (as gait) in
which the power/strength demands are below the levels of reductions in power/strength
that fatiguing protocols could induce.
Although these two hypothetical explanations are described separately, those
arguments might be complementary to elucidate the unexpected increase in gait velocity
after fatigability. However, to the best of our knowledge, there is no direct evidence that
could support these two hypothetical explanations. Accordingly, future studies aiming to
verify the effects of performance fatigability on walking should measure fatigability in a
broader domain (e.g., physiological and biomechanical) combined with assessments of
neuromuscular control, kinetics, stability, and kinematics of gait. Fatiguing protocols should
consider the specificity of muscles on gait and populations since most studies induced
fatigability on knee extensors despite the fact that in old populations mainly, the
plantarflexors thrust is the putative mechanism driving gait. Additionally, study designs
should consider long-distance walking in a less controlled environment (outside walking) -
most studies assessed short-distance (~10m) lab walking tasks since it may interfere with
movement economy and affect gait velocity. These protocol characteristics may avoid
alternative explanations that the increase in gait velocity induced by performance
fatigability may be a strategy of finishing the task rapidly.
5
Also, protocols comparing
maximum vs. self-selected speed after muscle fatigability would provide information on
whether underlying neuromechanims related to fatigability-induced gait changes support
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the usual, yet unexpected, increase in gait velocity.
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review with new insights on internal models and posture-movement coordination. Hum
Mov Sci. 2015;44:225–33.
3. Santos PCR, Barbieri FA, Zijdewind I, Gobbi LTB, Lamoth C, Hortobágyi T. Effects of
experimentally induced fatigue on healthy older adults’ gait: A systematic review. PLoS
One. 2019;14(12):e0226939. 10.1371/journal.pone.0226939
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Gait Posture. 2014;39(3):985–90. 10.1016/J.GAITPOST.2013.12.021
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10.1016/j.gaitpost.2016.04.002
8. Santos PCR, Lamoth CJC, Barbieri FA, Zijdewind I, Gobbi LTB, Hortobágyi T. Age-specific
modulation of intermuscular beta coherence during gait before and after experimentally
induced fatigue. Sci Rep. 2020;10(1). 10.1038/s41598-020-72839-1
9. Sotiropoulos K, Smilios I, Christou M, Barzouka K, Spaias A, Douda H, et al. Effects of
warm-up on vertical jump performance and muscle electrical activity using half-squats at
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10. Hak L, Houdijk H, Steenbrink F, Mert A, Van der Wurff P, Beek PJ, et al. Speeding up or
slowing down?: Gait adaptations to preserve gait stability in response to balance
perturbations. Gait Posture. 2012;36(2):260–4. 10.1016/j.gaitpost.2012.03.005
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Citation: Santos PCR, Lamoth C, Vuillerme N, Barbieri FA. (2021). Faster walking under muscle fatigability: a strategy
to improve stability or muscle post-activation effect?. Brazilian Journal of Motor Behavior, 15(3): 149-152.
Editors: Dr Fabio Augusto Barbieri - São Paulo State University (UNESP), Bauru, SP, Brazil; 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.
Section Editors (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:© 2021 Santos, Lamoth, Vuillerme 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: This work was partially supported by CNPq (FAB, project number: #445438/2014-2).
Competing interests: The authors have declared that no competing interests exist.
DOI:!https://doi.org/10.20338/bjmb.v15i3.241