Dexterous Manipulation During Rhythmic Arm Movements in Mars, Moon, and Micro-Gravity

Predicting the consequences of one’s own movements can be challenging when confronted with completely novel environmental dynamics, such as microgravity in space. The absence of gravitational force disrupts internal models of the central nervous system (CNS) that have been tuned to the dynamics of a constant 1-g environment since birth. In the context of object manipulation, inadequate internal models produce prediction uncertainty evidenced by increases in the grip force (GF) safety margin that ensures a stable grip during unpredicted load perturbations. This margin decreases with practice in a novel environment. However, it is not clear how the CNS might react to a reduced, but non-zero, gravitational field, and if adaptation to reduced gravity might be beneficial for subsequent microgravity exposure. That is, we wondered if a transfer of learning can occur across various reduced-gravity environments. In this study, we investigated the kinematics and dynamics of vertical arm oscillations during parabolic flight maneuvers that simulate Mars gravity, Moon gravity, and microgravity, in that order. While the ratio of and the correlation between GF and load force (LF) evolved progressively with practice in Mars gravity, these parameters stabilized much quicker to subsequently presented Moon and microgravity conditions. These data suggest that prior short-term adaptation to one reduced-gravity field facilitates the CNS’s ability to update its internal model during exposure to other reduced gravity fields

GRIP: Dexterous Manipulation of Objects in Weightlessness

The aim of the GRIP experiment is to investigate how gravity impacts the kinematics and dynamics of the upper limb during dexterous manipulation of objects and how the central nervous system adapts to long-term exposure to microgravity and subsequently back to Earth gravity. Hence, we proposed to conduct a set of experiments on healthy human subjects, involving the manipulation of an instrumented object during exposure to normal and microgravity, and to study how the central nervous system adapts motor control in order to cope with the new physical environment. More particularly, the coordination between the grasping force (or grip force, GF) and the load force (LF) is studied, as well as the adaptation of the movement dynamics and kinematics and the interaction between cognitive and sensory cues that establish a reference frame for the human brain. Here we describe the background motivation, the parabolic flight tests that initiated the scientific hypotheses and the technical and scientific process that led to the implementation of the GRIP experiment currently on board the International Space Station (ISS)

Short- and long-term adaptation of grip dynammics and arm kinematics to altered gravito-inertial environments

During object manipulation on Earth, muscular activities reflect an anticipation of the force of gravity. These loads must be compensated for or can be used to save muscular effort as well as to improve limb position sense. Furthermore, the gravitational vector constitutes a very important reference axis for spatial orientation. Given the promising future of Space exploration, a good understanding of the role played by gravity in sensorimotor control and of how the central nervous system adapts to novel gravito-inertial backgrounds is crucial. In this thesis, we study the dynamics of finger forces and the kinematics of the arm during object manipulation in humans exposed to such altered gravito-inertial environments. We first explore the coordination between arm movements and finger forces in Mars, Moon and micro- gravity during parabolic flight maneuvers. We then study sensorimotor coordination in upright and upside-down participants on the ground to test the contributions of body-centered and gravity-centered reference frames to upper-limb motor control. Finally, we study sensorimotor coordination in astronauts and observe that finger forces are finely tuned to object properties and to movement-induced inertial loads, both on the ground and in the weightless environment of the International Space Station. However, gravity appears to be critical to maintain movement accuracy in the absence of vision. These works contribute to our understanding of how gravity is accounted for during motor planning and control and of the impacts of novel gravito-inertial contexts on upper-limb motor control.(FSA - Sciences de l'ingénieur) -- UCL, 202

Dexterous Manipulation During Rhythmic Arm Movements in Mars, Moon, and Micro-Gravity.

Predicting the consequences of one's own movements can be challenging when confronted with completely novel environmental dynamics, such as microgravity in space. The absence of gravitational force disrupts internal models of the central nervous system (CNS) that have been tuned to the dynamics of a constant 1- environment since birth. In the context of object manipulation, inadequate internal models produce prediction uncertainty evidenced by increases in the grip force (GF) safety margin that ensures a stable grip during unpredicted load perturbations. This margin decreases with practice in a novel environment. However, it is not clear how the CNS might react to a reduced, but non-zero, gravitational field, and if adaptation to reduced gravity might be beneficial for subsequent microgravity exposure. That is, we wondered if a transfer of learning can occur across various reduced-gravity environments. In this study, we investigated the kinematics and dynamics of vertical arm oscillations during parabolic flight maneuvers that simulate Mars gravity, Moon gravity, and microgravity, in that order. While the ratio of and the correlation between GF and load force (LF) evolved progressively with practice in Mars gravity, these parameters stabilized much quicker to subsequently presented Moon and microgravity conditions. These data suggest that prior short-term adaptation to one reduced-gravity field facilitates the CNS's ability to update its internal model during exposure to other reduced gravity fields

Distinct adaptation patterns between grip dynamics and arm kinematics when the body is upside-down

In humans, practically all movements are learnt and performed in a constant gravitational field. Yet, studies on arm movements and object manipulation in parabolic flight have highlighted very fast sensorimotor adaptations to altered gravity environments. Here, we wondered if the motor adjustments observed in those altered gravity environments could also be observed on Earth in a situation where the body is upside-down. To address this question, we asked participants to perform rhythmic arm movements in two different body postures (right-side-up and upside-down) while holding an object in precision grip. Analyses of grip-load force coordination and of movement kinematics revealed distinct adaptation patterns between grip and arm control. Grip force and load force were tightly synchronized from the first movements performed in upside-down posture, reflecting a malleable allocentric grip control. In contrast, velocity profiles showed a more progressive adaptation to the upside-down posture and reflected an egocentric planning of arm kinematics. In addition to suggesting distinct mechanisms between grip dynamics and arm kinematics for adaptation to novel contexts, these results also suggest the existence of general mechanisms underlying gravity-dependent motor adaptation that can be used for fast sensorimotor coordination across different postures on Earth and, incidentally, across different gravitational conditions in parabolic flights, in human centrifuges, or in Space. NE

Troubles du bas appareil urinaire chez des patients atteints de la sclérose en plaques et kinésithérapie pelvi-périnéale : revue systématique

But : Notre but était d’objectiver l’efficacité de la kinésithérapie pelvi-périnéale pour la prise en charge des troubles du bas appareil urinaire des patients atteints de sclérose en plaques. Matériel : La revue de la littérature a été effectuée via PubMed, PEDro, Scopus et Cochrane Library. Les termes utilisés étaient multiple sclerosis, bladder dysfunction, overactive bladder, detrusor hyperreflexia, urge incontinence, urgency, stress incontinence, pelvic floor muscle, biofeedback, PTNS, tibial nerve, bladder training, physical therapy, physiotherapy, conservative treatment et behavioral therapy. Résultats : Six articles randomisés incluant 289 patients ont été sélectionnés. Quatre présentaient de bonnes qualités méthodologiques. Les paramètres qui étaient toujours significativement améliorés concernaient : le nombre d’épisodes d’incontinence urinaire (diminué de 64 % à 86 % après le traitement par rapport au début du traitement), la qualité de vie (p ≤ 0,001), la sévérité des symptômes irritatifs (diminuée de plus de 50 % après le traitement par rapport au début du traitement) et la nycturie (p = 0,035 à p < 0,001). La limitation d’activité, la restriction de participation, le débit maximum et le volume uriné ainsi que la pollakiurie n’étaient significativement améliorés que dans certaines études. Conclusions : La kinésithérapie pelvi-périnéale semblait efficace pour la prise en charge des problèmes du bas appareil urinaire des patients atteints modérément de la sclérose en plaques. Cependant, les résultats n’étaient basés que sur six études dont quatre de qualités méthodologiques satisfaisantes. Des recommandations sont difficiles à établir.Aim: To assess the effectiveness of conservative therapeutic approaches in a multiple sclerosis population. Material: Review was performed in PubMed, PEDro, Scopus and Cochrane Library using combinations of the following keywords: multiple sclerosis; bladder dysfunction; overactive bladder; detrusor hyperreflexia; urge incontinence; urgency; stress incontinence; pelvic floor muscle; biofeedback; PTNS; tibial nerve; bladder training; physical therapy; physiotherapy; conservative treatment and behavioral therapy. Results: Six randomized articles including 289 patients were selected. Four papers exhibited strong scores for the methodological quality assessment. The parameters always significantly improved concerned: number of incontinence episodes (decreased from 64% to 86% after treatment versus before treatment), quality of life (P ≤ 0.001), severity of irritative symptoms (decreased by more than 50% after treatment versus before treatment), and nocturia (P = 0.035 to P < 0.001). Activities and participation, maximum flow rate, mean voided volume and daytime frequency were not significantly improved in all trials. Conclusions: The physical therapy techniques could be effective for the treatment of urinary disorders in multiple sclerosis populations with mild disability. However, the analyses are based on six studies within only four showed good methodological quality. No strong conclusions regarding treatment approaches can be drawn from this review

A haptic illusion created by gravity

Summary: Human dexterity requires very fine and efficient control of fingertip forces, which relies on the integration of cutaneous and proprioceptive feedback. Here, we examined the influence of gravity on isometric force control. We trained participants to reproduce isometric vertical forces on a dynamometer held between the thumb and the index finger in normal gravity and tested them during parabolic flight creating phases of microgravity and hypergravity, thereby strongly influencing the motor commands and the proprioceptive feedback. We found that gravity creates the illusion that upward forces are larger than downward forces of the same magnitude. The illusion increased under hypergravity and was abolished under microgravity. Gravity also affected the control of the grip force employed to secure the grasp. These findings suggest that gravity biases the haptic estimation of forces, which has implications for the design of haptic devices to be used during flight or space activities

Kinésithérapie et symptômes du bas appareil urinaire chez des patients atteints de la sclérose en plaques : étude contrôlée randomisée

ABSTRACT AIM: this randomized controlled trial compare the efficacy of pelvic floor muscle training vs. transcutaneous posterior tibial nerve stimulation. PATIENTS AND METHODS: inclusion criteria were EDSS score < 7 and presence of lower urinary tract symptoms. Exclusion criteria were multiple sclerosis relapse during the study, active urinary tract infection and pregnancy. The primary outcome was quality of life (SF-Qualiveen questionnaire). Secondary outcomes included overactive bladder (USP questionnaire) score and frequency of urgency episodes (3-day bladder diary). Sample size was calculated after 18 patients were included. Data analysis was blinded. Each patient received 9 sesions of 30 minutes weekly. Patients were randomized in pelvic floor muscles exercices with biofeedback group (muscle endurance and relaxation) or transcutaneous posterior tibial nerve stimulation group (rectangular alternative biphasic current with low frequency). RESULTS: a total of 31 patients were included. No difference appeared between groups for quality of life, overactive bladder and frequency of urgency episodes (respectively p = 0.197, p = 0.532 et p = 0788). These parameters were significantly improved in pelvic floor muscle training group (n = 16) (respectively p = 0,004, p = 0,002 et p = 0,006) and in transcutaneous posterior tibial nerve stimulation group (n = 15) (respectively p = 0,001, p = ˂ 0,001 et p = 0,031). CONCLUSIONS: pelvic floor muscle training and transcutaneous posterior tibial nerve stimulation improved in the same way symptoms related to urgency in MS patients with mild disability. Keywords: multiple sclerosis; physiotherapy; lower urinary tract dysfunction; pelvic floor muscles training; posterior tibial nerve; rehabilitation. RESUME BUT: cet essai contrôlé randomisé comparait l’efficacité des exercices du plancher pelvien vs stimulation transcutanée du nerf tibial postérieur. PATIENTS ET METHODES: les critètres d’inclusion étaient un score EDSS < 7 et présence de symptômes du bas appareil urinaire. Les critères d’exclusion étaient une poussée de la maladie durant l’étude, une infection urinaire ou une grossesse. Le résultat principal concernait la qualité de vie (questionnaire SF-Qualiveen). Les résultats secondaires impliquaient un score d’hyperactivité vésicale (questionnaire USP) et la fréquence des urgences mictionnelles (catalogue mictionnel). Le calcul de la taille de l’échantillon était effectué après l’inclusion de 18 sujets. Les données était analysées en aveugle. Chaque patient suivait 9 séances hebdomadaires de 30 minutes comprenant aléatoirement soit des exercices du plancher pelvien avec biofeedback (travail de l’endurance et du relâchement périnéal), soit des stimulations transcutanées du nerf tibial postérieur (courant rectangulaire alternatif bi-phasique de basse fréquence). RESULTATS: au total, 31 patients étaient inclus. Aucune différence n’apparaissait entre les groupes pour la qualité de vie, l’hyperactivité vésicale et la fréquence des urgences mictionnelles journalière (respectivement p = 0.197, p = 0.532 et p = 0788). Ces paramètres étaient significativement améliorés dans le groupe exercices du plancher pelvien (n = 16) (respectivement p = 0,004, p = 0,002 et p = 0,006) et dans le groupe stimulation du nerf tibial (n = 15) (respectivement p = 0,001, p = ˂ 0,001 et p = 0,031). CONCLUSION: Les exercices du plancher pelvien ainsi que la stimulation transcutanée du nerf tibial postérieur amélioraient identiquement les symptômes liés à l’urgenturie chez des patients atteints modérément de la sclérose en plaques. Mots clés: sclérose en plaques ; kinésithérapie ; troubles du bas appareil urinaire ; exercices du plancher pelvien ; nerf tibial postérieur ; réadaptation

Arthroscopic Double-Layer Lasso Loop Technique to Repair Delaminated Rotator Cuff Tears.

To evaluate the arthroscopic double-layer lasso loop repair technique for delaminated posterosuperior rotator cuff tears. Forty-one patients underwent arthroscopic rotator cuff repair of a delaminated posterosuperior rotator cuff tear by the double-layer lasso loop technique. Their preoperative and postoperative clinical and functional scores were compared to evaluate surgical outcomes. The prerequisite for inclusion was a minimum follow-up period of 2 years. We excluded patients with a history of shoulder surgery before the double-layer lasso loop repair. Statistically significant improvements (P < .001) were found in the Constant score (54 vs 83) and University of California, Los Angeles functional score (6.4 vs 9.5). Pain and strength improved according to the Jobe test, bear-hug test, belly-press test, Gerber lift-off test, and external rotation test (P < .001). No significant difference in strength was noted between the operated and nonoperated sides. There was only 1 complete rerupture (3.1%), whereas 5 patients (15.6%) had partial ruptures. The arthroscopic double-layer lasso loop repair technique for delaminated posterosuperior rotator cuff tears is an effective procedure. Our series showed a low rerupture rate. At a mean follow-up of 44 months, postoperative recovery with resultant functional, pain, and patient satisfaction scores was good to excellent and was comparable with the nonoperated side. Level IV, case series