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Diffusion in Phase Space as a Tool to Assess Variability of Vertical Centre-of-Mass Motion during Long-Range Walking
06 février 2023,
- CeREF Santé
- CeREF Technique
,
- Article scientifique
Article scientifique
When a Hamiltonian system undergoes a stochastic, time-dependent anharmonic perturbation,
the values of its adiabatic invariants as a function of time follow a distribution whose shape
obeys a Fokker–Planck equation. The effective dynamics of the body’s centre-of-mass during human
walking is expected to represent such a stochastically perturbed dynamical system. By studying, in
phase space, the ...
Adiabatic Invariant of Center-of-Mass Motion during Walking as a Dynamical Stability Constraint on Stride Interval Variability and Predictability
09 septembre 2022,
- HE Louvain en Hainaut
,
- Article scientifique
Article scientifique
Human walking exhibits properties of both stability and variability. On the one
hand, the variability of the interval of time between heel strikes is autocorrelated, i.e., not randomly
organized. On the other hand, walking is highly stereotyped and arguments from general mechanics
suggest that the stability of gait can be assessed according to invariant properties. This study aims
at proposing ...
Motor strategies and adiabatic invariants: The case of rhythmic motion in parabolic flights
05 août 2021,
- CeREF Technique
,
- Article scientifique
Article scientifique
The role of gravity in human motor control is at the same time obvious and difficult to isolate. It can be
assessed by performing experiments in variable gravity. We propose that adiabatic invariant theory may be used
to reveal nearly conserved quantities in human voluntary rhythmic motion, an individual being seen as a complex
time-dependent dynamical system with bounded motion in phase space. ...
Fine adaptive precision grip control without maximum pinch strength changes after upper limb neurodynamic mobilization
30 juin 2021,
- HE Louvain en Hainaut
,
- Article scientifique
Article scientifique
Before and immediately after passive upper limb neurodynamic mobilizations targeting the median
nerve, grip ( GF ) and load ( LF ) forces applied by the thumb, index and major fingers (three-jaw chuck
pinch) were collected using a manipulandum during three different grip precision tasks: grip-lifthold-
replace (GLHR), vertical oscillations (OSC), and vertical oscillations with up and down ...
Benefits of nonlinear analysis indices of walking stride interval in the evaluation of neurodegenerative diseases
12 décembre 2020,
- HE Louvain en Hainaut
,
- Article scientifique
Article scientifique
Indices characterising the long-range temporal structure of walking stride interval (SI) variability such as Hurst exponent (H) and fractal dimension (D) may be used in addition to indices measuring the amount of variability like the coefficient of variation (CV). We assess the added value of the former indices in a clinical neurological context. Our aim is to demonstrate that they provide a clinical ...
Adiabatic invariants drive rhythmic human motion in variable gravity
01 décembre 2020,
- CeREF Technique
,
- Article scientifique
Article scientifique
Voluntary human movements are stereotyped. When modeled in the framework of classical mechanics they are expected to minimize cost functions that may include energy, a natural candidate from a physiological point of view also. In time-changing environments, however, energy is no longer conserved—regardless of frictional energy dissipation—and it is therefore not the preferred candidate for any cost ...
Higher-derivative harmonic oscillators: stability of classical dynamics and adiabatic invariants
06 janvier 2019,
- CERISIC
,
- Article scientifique
Article scientifique
he status of classical stability in higher-deriv- ative systems is still subject to discussions. In this note, we argue that, contrary to general belief, many higher-derivative systems are classically stable. The main tool to see this prop- erty are Nekhoroshev’s estimates relying on the action-angle formulation of classical mechanics. The latter formulation can be reached provided the Hamiltonian ...
Fractal analyses reveal independent complexity and predictability of gait
28 novembre 2017,
- HE Louvain en Hainaut
,
- Livre/Ouvrage ou monographie
Livre/Ouvrage ou monographie
Locomotion is a natural task that has been assessed for decades and used as a proxy to highlight impairments of various origins. So far, most studies adopted classical linear analy- ses of spatio-temporal gait parameters. Here, we use more advanced, yet not less practical, non-linear techniques to analyse gait time series of healthy subjects. We aimed at finding more sensitive indexes related to ...