Biology subjects

Ronsse, R.

Publications and source records attributed to Ronsse, R..

3 recordsLinked to original sources

bioRxiv2025

Measured and modelled transitions between self-paced walking and synchronization with rhythmic auditory cues

Constraining gait rhythm with a metronome has been shown to influence gait pattern in many different ways. While rhythmic cues can improve several parameters in some clinical populations, they do alter the long-range autocorrelations naturally exhibited in series of stride durations. However, transitions between walking with and without a metronome (and vice versa) have not been measured; it is therefore unclear how people adapt to such a change in task. To address this gap, a total of 21 healthy volunteers were asked to walk overground under three conditions: one unconstrained control condition, followed by two conditions in which a metronome was activated during either the first or second half of the trial to test both transitions. The long-range autocorrelations were assessed over a sliding window on the stride series to measure their evolution. Our observations were reproduced with a computational model allowing us to relate sudden changes in movement parameters to the long-range autocorrelations, which are typically measured over longer timescales. The results showed a clear transition in both conditions involving a metronome, with long-range autocorrelations of the series of stride durations gradually reduced when the metronome was turned on and recovered when it was turned off. In these two conditions, the change in long-range autocorrelations could be reproduced in the model by an instantaneous switching of the control policy associated with the presence or not of the metronome, suggesting that long-range autocorrelations emerge from a flexible control strategy that rapidly regulates timing and amplitude parameters according to task requirements. Significant statementThrough an experiment involving transitions between walking with and without a metronome, we studied how people adapt to such a change of task by measuring the evolution of long-range autocorrelations (LRA) in the stride series. The results were reproduced in a model by an instantaneous change in the control policy, which validates the hypothesis that LRA emerge from a flexible control that rapidly regulates timing and amplitude parameters according to task requirements.

neuroscience↗

bioRxiv2025

Speeding up, not slowing down, decreases the energy needed to control walking balance

There is a metabolic cost associated with controlling walking balance but it remains unclear to what extent sagittal plane balance control contributes to this cost. Furthermore, sagittal plane balance control strategies vary with speed but it is unclear whether this also leads to a speed-dependent balance-related metabolic cost. Here, we explored the metabolic cost of stabilizing walking in the sagittal plane across speeds and its relationship with balance control strategies. To this aim, we applied continuous treadmill belt speed perturbations (standard deviation of 0.13 ms-1) to 22 healthy individuals walking at 0.8, 1.2, and 1.6 m/s. We evaluated changes in metabolic energy consumption and balance control strategies between perturbed and unperturbed walking and explored relationships between both. Perturbations induced larger increases in metabolic rate and changes in balance control strategies at slower than faster walking speeds, suggesting that walking is more robust against perturbations at faster speeds. Perturbations increased the metabolic rate by 16.7% at the slowest versus 4.6% at the fastest walking speed. When perturbed, subjects took shorter, wider, and more variable steps, and variability in ankle muscle activation increased but most changes were larger at slower speeds. Metabolic rate increased more due to perturbations in individuals who reduced step length more, i.e. relied more on anticipatory adjustments of the walking pattern. Our findings are especially relevant for explaining the increased metabolic cost of individuals with mobility impairments, who often walk slower and have altered balance control.

physiology↗

bioRxiv2022

On the role of tail in stability and energetic cost of bird flapping flight

Migratory birds travel over impressively long distances. Consequently, they have to adopt flight regimes being both efficient - in order to spare their metabolic resources - and robust to perturbations. This paper investigates the relationship between both aspects, i.e. mechanical performance and stability in flapping flight of migratory birds. Relying on a poly-articulated wing morphing model and a tail-like surface, several families of steady flight regime have been identified and analyzed. These families differ by their wing kinematics and tail opening. A systematic parametric search analysis has been carried out, in order to evaluate power consumption and cost of transport. A framework tailored for assessing limit cycles, namely Floquet theory, is used to numerically study flight stability. Our results show that under certain conditions, an inherent passive stability of steady and level flight can be achieved. In particular, we find that progressively opening the tail leads to passively stable flight regimes. Within these passively stable regimes, the tail can produce either upward or downward lift. However, these configurations entail an increase of cost of transport at high velocities penalizing fast forward flight regimes. Our model-based predictions suggest that long range flights require a furled tail configuration, as confirmed by field observations, and consequently need to rely on alternative mechanisms to stabilize the flight.

bioengineering↗