Biology subjects

Jubeau, M.

Publications and source records attributed to Jubeau, M..

3 recordsLinked to original sources

bioRxiv2026

Recurrent inhibition, not presynaptic inhibition, contributes to the velocity-dependent control of motoneuron output during eccentric contractions

It is well documented that both motoneuron output and the effectiveness of activated Ia afferents to discharge soleus -motoneurons decrease during eccentric (muscle lengthening) contractions. Evidence suggests that these modulations can be explained by recurrent inhibition and greater presynaptic inhibition of Ia afferents. However, the influence of angular velocity on the modulation of the effectiveness of activated Ia afferents to discharge -motoneurons observed during eccentric contractions remains unclear. We investigated the influence of angular velocity on spinal mechanisms involved in the effectiveness of activated Ia afferents to discharge -motoneurons during eccentric plantar flexor contractions using 16 healthy adults. We used both simple and conditioned Hoffmann reflex with different conditioning techniques to assess presynaptic inhibition, heteronymous Ia facilitation and heteronymous recurrent inhibition coupled with electromyography during eccentric contractions of the plantar flexors at three angular velocities. Our results showed that during eccentric contractions, the effectiveness of Ia afferents to discharge -motoneurons was lower at 90{degrees}{middle dot}s-{superscript 1} than 60{degrees}{middle dot}s-{superscript 1} and 20{degrees}{middle dot}s-{superscript 1} angular velocities. A similar velocity-dependent pattern was observed for heteronymous recurrent inhibition, decreasing at 90{degrees}{middle dot}s-{superscript 1} when compared with 60{degrees}{middle dot}s-{superscript 1} and 20{degrees}{middle dot}s-{superscript 1}. In contrast, presynaptic inhibition of Ia afferents was not different between the velocities. These demonstrate a differential influence of angular velocity on spinal recurrent inhibitory mechanisms during eccentric contractions and support distinct functional roles of recurrent and presynaptic inhibition in modulating -motoneurons discharge with increasing movement velocity. The findings provide new insights into the velocity-dependent and mechanism-specific modulation of spinal inhibitory circuits during eccentric contractions. KEY POINTSO_LIDuring eccentric contractions in soleus muscle, the effectiveness of activated Ia afferents to discharge -motoneurones decreases with increasing angular velocity, indicating a velocity-dependent modulation. C_LIO_LIPresynaptic inhibition of Ia afferents does not differ between angular velocities, suggesting that it does not contribute to the observed changes. C_LIO_LIHeteronymous recurrent inhibition from the quadriceps to the soleus increases with angular velocity, indicating that increasing movement velocity promotes a functional reorganization of intermuscular recurrent inhibition. C_LIO_LIThese findings suggest a differential functional role of the two spinal inhibitory mechanisms, indicating that increasing angular velocity primarily influences recurrent postsynaptic inhibition rather than presynaptic inhibition. C_LI

neuroscience↗

bioRxiv2026

Mental fatigue impairs cycling endurance performance and perception of effort, but not muscle activation

Mental fatigue is induced by prolonged engagement in cognitively demanding tasks and impairs endurance performance. The neuropsychophysiological mechanisms underlying this decreased performance remain unclear, with suggestion that mental fatigue may disrupt motor command and consequently muscle activation. We aimed to test this hypothesis in a repeated cross-over design study in which 18 participants completed two experimental sessions involving a time-to-task failure cycling test at 80% of peak power output. Each cycling task was preceded by 1h of a prolonged Stroop task (Stroop condition) or a neutral control task (Control condition). Mental fatigue was assessed using a visual analog scale anchored with "not fatigued at all" and "extremely fatigued. Perception of effort and surface electromyography from ten lower-limb muscles of the right leg were recorded at regular intervals during cycling. Mental fatigue was higher in the Stroop compared to the Control condition (p = .002). Endurance cycling time was shorter in the Stroop than in the Control condition (887 {+/-} 284 s vs. 999 {+/-} 379 s, respectively; -111 {+/-} 160 s, p = .009). No significant differences in electromyography parameters were observed between Stroop and Control conditions, for any muscle (p > .05). Perception of effort was higher in the Stroop condition from the onset of the cycling task (p = .006), and the rate of increase in perception of effort was significantly higher in the Stroop than Control condition (p = .031). Our findings do not support the hypothesis that mental fatigue alters motor control or increases central motor command, as no changes in muscle activation were detected. Conversely, our results reinforce the notion that prolonged cognitive engagement impairs endurance performance primarily through an increased perception of effort. Future research should consider combining surface electromyography with more sensitive neurophysiological techniques to investigate potential subtle changes in motor drive during dynamic, whole-body tasks under mental fatigue.

physiology↗

bioRxiv2024

Muscle length modulates recurrent inhibition and post-activation depression differently according to contraction type

It is well documented that, in soleus, motoneuron output and the effectiveness of activated Ia afferents to discharge -motoneurons both decrease during eccentric contractions. Evidence suggests that these regulations can be explained by (1) recurrent inhibition and (2) greater post-activation depression by primary afferent depolarization. However, the influence of muscle length on the regulation of the effectiveness of Ia afferents to discharge -motoneurons observed during eccentric contractions remains unclear. We conducted a study on 16 healthy young individuals. We used simple and conditioned Hoffmann reflex with different conditioning techniques such as paired H reflex, D1 method and heteronymous Ia facilitation coupled with electromyography during eccentric, isometric and concentric contractions at long, intermediate and short soleus muscle lengths. Our results confirm that during eccentric contraction the effectiveness of Ia afferents to discharge U-motoneurons decreases only at intermediate and short muscle lengths but is similar between all contraction types at long muscle length. Findings are similar for recurrent inhibition. Post-activation depression is significantly more pronounced during eccentric contractions compared with isometric and concentric contractions at long muscle length. Our analysis also shows that recurrent inhibition and post-activation depression are greater at long muscle length compared with short muscle length, whatever the contraction type. These new findings demonstrate an important influence of muscle length on the activity of spinal regulatory mechanisms and the effectiveness of activated Ia afferents to discharge -motoneurons during eccentric contractions.

neuroscience↗