Changes in corticospinal transmission following 8 weeks of ankle joint immobilization

Joint immobilization has previously been shown to modulate corticospinal excitability. The present study investigated changes in the excitability of distinct fractions of the corticospinal pathway by means of conditioning the H-reflex with transcranial magnetic stimulation (TMS) of the primary motor cortex (Hcond). This method allows assessment of transmission in fast (monosynaptic) and slow(er) (polysynaptic) corticospinal pathways.Methods: 9 subjects underwent 8 weeks of unilateral ankle joint immobilization during daytime, 7 subjects served as controls. The measures obtained before and after immobilization included stretch- and H-reflexes assessing excitability of the spinal reflex circuitries, TMS recruitment curves estimating overall changes in corticospinal excitability, and Hcond.Results: TMS recruitment curves showed an overall increase in corticospinal excitability following immobilization. Importantly, Hcond revealed significant facilitation of conditioned reflexes, but only for longer conditioning intervals, suggesting that immobilization increased excitability only of slower, indirect corticospinal pathways. No changes were observed in the control group. Immobilization had no significant effects on spinal reflex measures.Conclusions: 8 weeks of ankle joint immobilization was accompanied by pathway-specific modulation of corticospinal transmission.Significance: It is particularly interesting that fast corticospinal projections were unaffected as these are involved in controlling many, if not most, movements in humans

The relationship between exercise-induced muscle fatigue, arterial blood flow and muscle perfusion after 56 days of muscle unloading

In the light of the dynamic nature of habitual plantar flexor activity, we utilized an incremental isokinetic exercise test (IIET) to assess the work-related power deficit (WoRPD) as a measure for exercise-induced muscle fatigue before and after prolonged calf muscle unloading and in relation to arterial blood flow and muscle perfusion. Eleven male subjects (31 ± 6 years) wore the HEPHAISTOS unloading orthosis unilaterally for 56 days. It allows habitual ambulation while greatly reducing plantar flexor activity and torque production. Endpoint measurements encompassed arterial blood flow, measured in the femoral artery using Doppler ultrasound, oxygenation of the soleus muscle assessed by near-infrared spectroscopy, lactate concentrations determined in capillary blood and muscle activity using soleus muscle surface electromyography. Furthermore, soleus muscle biopsies were taken to investigate morphological muscle changes. After the intervention, maximal isokinetic torque was reduced by 23·4 ± 8·2% (P<0·001) and soleus fibre size was reduced by 8·5 ± 13% (P = 0·016). However, WoRPD remained unaffected as indicated by an unchanged loss of relative plantar flexor power between pre- and postexperiments (P = 0·88). Blood flow, tissue oxygenation, lactate concentrations and EMG median frequency kinematics during the exercise test were comparable before and after the intervention, whereas the increase of RMS in response to IIET was less following the intervention (P = 0·03). In conclusion, following submaximal isokinetic muscle work exercise-induced muscle fatigue is unaffected after prolonged local muscle unloading. The observation that arterial blood flow was maintained may underlie the unchanged fatigability

Quantum cascade laser frequency stabilisation at the sub-Hz level

Quantum Cascade Lasers (QCL) are increasingly being used to probe the mid-infrared "molecular fingerprint" region. This prompted efforts towards improving their spectral performance, in order to reach ever-higher resolution and precision. Here, we report the stabilisation of a QCL onto an optical frequency comb. We demonstrate a relative stability and accuracy of 2x10-15 and 10-14, respectively. The comb is stabilised to a remote near-infrared ultra-stable laser referenced to frequency primary standards, whose signal is transferred via an optical fibre link. The stability and frequency traceability of our QCL exceed those demonstrated so far by two orders of magnitude. As a demonstration of its capability, we then use it to perform high-resolution molecular spectroscopy. We measure absorption frequencies with an 8x10-13 relative uncertainty. This confirms the potential of this setup for ultra-high precision measurements with molecules, such as our ongoing effort towards testing the parity symmetry by probing chiral species

Développement d'une chaîne de synthèse de fréquences optiques (application a la mesure de la fréquence absolue d'un laser nd)

PARIS-CNAM (751032301) / SudocSudocFranceF

The HEPHAISTOS study: compliance and adherence with a novel orthotic device for calf muscle unloading

The present manuscript seeks to discuss methodological aspects regarding the application of the novel unloading orthosis 'HEPHAISTOS' that has been specifically developed to study physiological effects of muscular unloading without altering the impact of gravitational loading. The 'HEPHAISTOS' has been applied in an ambulatory clinical interventional study. During gait, the 'HEPHAISTOS' significantly reduces activation and force production of calf muscles while it completely retains body mass-related force on the tibia. Eleven healthy male subjects participated in the study and followed their normal everyday lives while wearing the orthosis. Several measurement sessions have been performed to investigate the time course of structural and functional adaptations during intervention and recovery. Follow-up measurements were performed for one year after the intervention. In consideration of the experiences of a unique ambulant unloading study, organizational and methodological recommendations are discussed in this manuscript. Activity monitoring data obtained with portable accelerometers reveal unchanged gait activities and good subject compliance throughout the intervention. Moreover, electromyography (EMG) and motion data investigating gait properties on reambulation day are illustrated. These data show that during the initial steps following removal of 'HEPHAISTOS', gait was significantly asynchronous indicating an acutely altered motor control in the unloaded lower leg muscles

Ultra-sonic testing of the splat-substrate interface

International audienc

WP6 follow-up: Studied measures within the French case

Note explicative concernant la mesure 0301A (couverture des sols nus en hiver), sur le département de la Manch

Influence of powder characteristics on the microstructure and bond strength of cold-sprayed aluminum coating

International audienceCold spray aluminum coatings are today developed for a wide range of applications such as the repair of aircraftcomponents, or additive manufacturing. However, powders specifically tailored for cold spray, are yet not availabledue to a rather low amount of results on the effect of powder characteristics on cold spray coatings properties. Theinfluence of powder morphology on the microstructure and bond strength of cold-sprayed aluminum coating isshown in this study. Aluminum powders with spherical and irregular particle shapes were selected and cold-sprayedonto shot-peened steel. These powders were mixed with two alumina powders with either a spherical or an angularparticle shape to improve coating properties. The effect of powder characteristics on coating microstructure wasstudied using X-Ray diffraction, optical and scanning electron microscopy. In addition, coating adhesion propertieswere determined using conventional pull-off testing. Aluminum coatings with extremely high adhesion weresuccessfully cold-sprayed on steel. Alumina addition reduced the porosity and increased the hardness of thealuminum coating. Aluminum-alumina mixtures with the same particle shape seem to be more suitable to obtaindense coatings on steel with a high bond strengt

WP6 follow-up: Feedback after the first field visits and interviews [Internal Communication]

ITAES - SPECIFIC TARGETED RESEARCH PROJECT n°SSPE-CT-2003-502070WP6 follow-up: Feedback after the first field visits and interviews [Internal Communication

WP6 follow-up: Feedback after the first field visits and interviews [Internal Communication]

ITAES - SPECIFIC TARGETED RESEARCH PROJECT n°SSPE-CT-2003-502070WP6 follow-up: Feedback after the first field visits and interviews [Internal Communication