Biology subjects

Crouzier, M.

Publications and source records attributed to Crouzier, M..

3 recordsLinked to original sources

bioRxiv2024

Estimation of the Achilles tendon twist in vivo by individual triceps surae muscle stimulation

The Achilles tendon (AT) is comprised of three distinct subtendons, each arising from the one of the three heads of the triceps surae muscles: gastrocnemius medialis (GM), gastrocnemius lateralis (GL) and soleus (SOL). These subtendons exhibit a twisted structure, classified as low (Type I), medium (Type II), and high (Type III) twist, based on cadaveric studies. Nevertheless, the in-vivo investigation of AT twist is notably scarce, resulting in a limited understanding of its functional significance. The aim of this study was to give insights into the complex 3D AT structure in vivo. 30 healthy participants underwent individual stimulation of each of the triceps surae muscles at rest with the foot attached to the pedal of an isokinetic dynamometer. Ultrasound images were captured to concomitantly examine the displacement of the superficial, middle and deep AT layers. SOL stimulation resulted in the highest AT displacement followed by GM and GL stimulation. Independent of the muscle stimulated, non-uniformity within the AT was observed with the deep layer exhibiting more displacement compared to the middle and superficial layers, hence important inter-individual differences in AT displacement were noticeable. By leveraging these individual displacement patterns during targeted stimulations in conjunction with cadaveric twist classifications providing insights into the area of each specific subtendon, our classification identified 19 subjects with a low and 11 subjects with a high AT twist. More research is needed to understand the complexity of the AT twisted structure in vivo to further understand its effect on AT properties and behaviour.

physiology↗

bioRxiv2024

Reduced intra-tendinous sliding in Achilles tendinopathy during active plantarflexion regardless of horizontal foot position

The Achilles tendon consists of three subtendons with the ability to slide relative to each other. As optimal intra-tendinous sliding is thought to reduce the overall stress in the tendon, alterations in sliding behavior could potentially play a role in the development of Achilles tendinopathy. The aims of this study were to investigate the difference in intra-tendinous sliding within the Achilles tendon during isometric contractions between asymptomatic controls and patients with Achilles tendinopathy and the effect of changing the horizontal foot position on intra-tendinous sliding in both groups. 29 participants (13 Achilles tendinopathy, 16 controls) performed isometric plantarflexion contractions at 60% of their maximal voluntary contraction (MVC), in toes-neutral, and at 30% MVC in toes-neutral, toes-in and toes-out positions during which ultrasound images were recorded. Intra-tendinous sliding was estimated as the superficial-to-middle and middle-to-deep relative displacement. Our results indicate that patients with Achilles tendinopathy present lower intra-tendinous sliding compared to asymptomatic controls. Regarding the horizontal foot position in both groups, the toes-out foot position resulted in increased sliding compared to both toes-neutral and toes-out foot position. We provided evidence that patients with Achilles tendinopathy show lower intra-tendinous sliding compared to asymptomatic controls. Since intra-tendinous sliding is a physiological feature of the Achilles tendon, the external foot position holds promise to increase sliding in patients with Achilles tendinopathy and promote healthy tendon behavior. Future research should investigate if implementing this external foot position in rehabilitation programs stimulates sliding within the Achilles tendon and improves clinical outcome.

pathology↗

bioRxiv2023

Estimates of persistent inward currents in lower limb muscles are not different between inactive, resistance-trained and endurance-trained young individuals

Persistent inward currents (PICs) increase the intrinsic excitability of -motoneurons. The main objective of this study was to determine whether estimates of -motoneuronal PIC magnitude is influenced by chronic endurance and resistance training. We also aimed to investigate whether there is a relationship in the estimates of -motoneuronal PIC magnitude between muscles. Estimates of PIC magnitude were obtained in three groups of young individuals: resistance-trained (n=12), endurance-trained (n=12), and inactive (n=13). We recorded high-density surface electromyography (HDsEMG) signals from tibialis anterior, gastrocnemius medialis, soleus, vastus medialis, and vastus lateralis. Then, signals were decomposed with convolutive blind source separation to identify motor units spike trains. Participants performed triangular isometric contractions to a peak of 20% of their maximum voluntary contraction. A paired-motor-unit analysis was used to calculate {Delta}F, which is assumed to be proportional to PIC magnitude. Despite the substantial differences in physical training experience between groups, we found no differences in {Delta}F, regardless of the muscle. Significant correlations of estimates of PICs magnitude were found between muscles of the same group (VL-VM, SOL-GM). Only one correlation (out of 8) between muscles of different groups was found (GM and TA). Overall, our findings suggest that estimates of PIC magnitude in the lower limb muscles are not influenced by physical training experience in healthy young individuals. They also suggest muscle-specific and muscle group-specific regulations of the diffuse monoamine inputs.

neuroscience↗