Mechanical determinants of 100-m sprint running performance

International audienceSprint mechanics and field 100-m performances were tested in 13 subjects including 9 non-specialists, 3 French national-level sprinters and a world-class sprinter, to further study the mechanical factors associated with sprint performance. 6-s sprints performed on an instrumented treadmill allowed continuous recording of step kinematics, ground reaction forces (GRF), and belt velocity and computation of mechanical power output and linear force–velocity relationships. An index of the force application technique was computed as the slope of the linear relationship between the decrease in the ratio of horizontal-to-resultant GRF and the increase in velocity. Mechanical power output was positively correlated to mean 100-m speed (P0.683; P0.21). Last, anthropometric data of body mass index and lowerlimb- to-height ratio showed no significant correlation with 100-m performance. We concluded that the main mechanical determinants of 100-m performance were (1) a ‘‘velocity-oriented’’ force–velocity profile, likely explained by (2) a higher ability to apply the resultant GRF vector with a forward orientation over the acceleration, and (3) a higher step frequency resulting from a shorter contact time

Impact of Emergent Cervical Carotid Stenting in Tandem Occlusion Strokes Treated by Thrombectomy: A Review of the TITAN Collaboration

Introduction: Endovascular therapy has been shown to be an effective and safe treatment for tandem occlusion. The endovascular therapeutic strategies for tandem occlusions strokes have not been adequately evaluated and the best approach is still controversial. The TITAN (Thrombectomy in TANdem occlusions) registry was a result of a collaborative effort to identify the best therapeutic approach for acute ischemic stroke due to tandem lesion. In this review, we aim to summarize the main findings of the TITAN study and discuss the challenges of treatment for tandem occlusion in the era of endovascular thrombectomy.Methods: A review of the data from the multicenter international observational and non-randomized TITAN registry was performed. The TITAN registry included acute ischemic stroke patients with tandem lesions (proximal intracranial occlusion and cervical carotid artery occlusion or stenosis>90%) who were treated with thrombectomy with or without carotid artery stenting.Results: Prior intravenous thrombolysis and emergent cervical carotid stenting were associated with higher reperfusion (mTICI 2b-3 and mTICI 3) rates at the end of the intervention. Poor outcome did not occur more frequently after stenting than after conservative treatment of the cervical carotid lesion. Emergent carotid stenting with antithrombotic agents and intracranial thrombectomy yielded higher reperfusion rate and good outcome (90 day mRS 0–2) compared to other strategies (carotid artery stenting and thrombectomy without antithrombotic, angioplasty and thrombectomy, or thrombectomy alone). Pretreatment intravenous thrombolysis was not associated with increased risk of hemorrhagic complications. Likewise, periprocedural unfractionated heparin did not modify the efficacy and safety results. Etiology of carotid artery lesion (atherosclerosis vs. dissection) did not emerge as predictor of outcome or recanalization.Conclusion: Emergent stenting of the cervical carotid lesion with antithrombotic agents in conjunction to thrombectomy appears to be the best treatment strategy for acute ischemic strokes with tandem lesions. These findings will be further investigated in the ongoing randomized controlled TITAN trial

Patent Foramen Ovale Closure or Anticoagulation vs. Antiplatelets after Stroke

BACKGROUND Trials of patent foramen ovale (PFO) closure to prevent recurrent stroke have been inconclusive. We investigated whether patients with cryptogenic stroke and echocardiographic features representing risk of stroke would benefit from PFO closure or anticoagulation, as compared with antiplatelet therapy. METHODS In a multicenter, randomized, open-label trial, we assigned, in a 1:1:1 ratio, patients 16 to 60 years of age who had had a recent stroke attributed to PFO, with an associated atrial septal aneurysm or large interatrial shunt, to transcatheter PFO closure plus long-term antiplatelet therapy (PFO closure group), antiplatelet therapy alone (antiplatelet-only group), or oral anticoagulation (anticoagulation group) (randomization group 1). Patients with contraindications to anticoagulants or to PFO closure were randomly assigned to the alternative noncontraindicated treatment or to antiplatelet therapy (randomization groups 2 and 3). The primary outcome was occurrence of stroke. The comparison of PFO closure plus antiplatelet therapy with antiplatelet therapy alone was performed with combined data from randomization groups 1 and 2, and the comparison of oral anticoagulation with antiplatelet therapy alone was performed with combined data from randomization groups 1 and 3. RESULTS A total of 663 patients underwent randomization and were followed for a mean (+/- SD) of 5.3 +/- 2.0 years. In the analysis of randomization groups 1 and 2, no stroke occurred among the 238 patients in the PFO closure group, whereas stroke occurred in 14 of the 235 patients in the antiplatelet-only group (hazard ratio, 0.03; 95% confidence interval, 0 to 0.26; P<0.001). Procedural complications from PFO closure occurred in 14 patients (5.9%). The rate of atrial fibrillation was higher in the PFO closure group than in the antiplatelet-only group (4.6% vs. 0.9%, P = 0.02). The number of serious adverse events did not differ significantly between the treatment groups (P = 0.56). In the analysis of randomization groups 1 and 3, stroke occurred in 3 of 187 patients assigned to oral anticoagulants and in 7 of 174 patients assigned to antiplatelet therapy alone. CONCLUSIONS Among patients who had had a recent cryptogenic stroke attributed to PFO with an associated atrial septal aneurysm or large interatrial shunt, the rate of stroke recurrence was lower among those assigned to PFO closure combined with antiplatelet therapy than among those assigned to antiplatelet therapy alone. PFO closure was associated with an increased risk of atrial fibrillation

Les adaptations croisées climatiques chez l humain (caractérisation, mécanismes et risques thermophysiologiques)

Les voyages transcontinentaux mais aussi les opérations militaires extérieures peuvent soumettre des personnes adaptées à une contrainte thermique donnée à une contrainte thermique opposée, les exposant à des risques médicaux thermophysiologiques (RMT) non évalués à ce jour. Cette situation recouvre le concept peu documenté des adaptations thermiques croisées (AC) dont les RMT sont inconnus. Utilisant des tests de sudation (Tdb=45 C, RH=10 %, 90 min) et des tests froids (Tdb=1 C, 120 min) chez l humain avant et après adaptation à la chaleur (28 j en Guyane) ou au froid (55 j en Arctique), nous avons caractérisé les AC chaleur/froid et froid/chaleur, décrit les mécanismes thermophysiologiques impliqués dans leur développement par manipulation en laboratoire des charges thermiques subies par 24 sujets et évalué les RMT. Une méthodologie générale pour l étude, la caractérisation et l évaluation des risques pour d autres AC est proposée afin d optimiser la prévention médicaleIntercontinental travels, but also overseas deployment of troops may submit adapted persons to a given thermal strain to an opposite thermal strain, exposing them to unassessed thermophysiological risks. This problem encompassed the poorly researched concept of thermal cross-adaptation. Using sweating tests (Tdb=45 C, RH=10 %, 90 min) and standard cold air tests (Tdb=1 C, 120 min) in humans, before and after heat acclimatization (28 d in French Guyana) or cold acclimatization (55 d in Artic), we characterized heat/cold and cold/heat cross-adaptations. The thermophysiological mechanisms involved in their development were described in 24 subjects submitted to different thermal loads. The resulting thermophysiological risks were evaluated. A methodology for studying, characterizing and assessing the medical risks for other cross-adaptations is proposed in order to optimize the medical preventionLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Le suivi médical du sportif en milieu libéral (étude des dossiers médicaux d'une population de cyclistes de tous les niveaux suivis par un médecin du sport de 1978 à 2001)

LYON1-BU Santé (693882101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Etude de la variabilité cardiaque nocturne au cours d'un cycle d'entraînement chez le coureur d'endurance

LYON1-BU Santé (693882101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

REPONSES PHYSIOLOGIQUES LORS DE L'EXPOSITION LOCALE DES EXTREMITES AU FROID CHEZ L'HOMME (ETUDE DE LA VARIABILITE DE LA VASODILATATION PARADOXALE)

LYON1-BU Santé (693882101) / SudocPARIS-BIUM (751062103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

MESURE DE LA FORCE MUSCULAIRE A PARTIR DE L'ACCELERATION APPLIQUEE A UNE CHARGE (RELATION FORCE-VITESSE DANS DES CONDITIONS BALISTIQUES (DOCTORAT : GENIE BIOMEDICAL))

LYON1-BU Santé (693882101) / SudocPARIS-BIUM (751062103) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Qualités neuro-musculaires et métabolisme du lactate (relation avec la performance sur 100 m et dans différentes spécialités athlétiques (400 à 1500 m))

Ce travail prote d'une part sur l'étude des facteurs mécaniques et physiologiques qui influencent la performance au cours du sprint. D'autre part, une analyse de l'aptitude à échanger et à éliminer le lactate a été réalisée afin de pourvoir établir une comparaison entre les coureurs de 100 m et ceux spécialistes de 400, 800 et 1500 m. Les courbes d'évolution de la concentration sanguine de lactate, lors de la récupération peuvent précisément être décrites par l'équation proposée par Freund et Gendry (1978) : [La](t) = [La](0) + A1(1-e-g1t) + A2(1-e-g2t) où g1 donne des informations sur l'aptitude à échanger le lactate des muscle précédemment actifs vers le sang, et g2 renseigne sur l'aptitude à éliminer le lactate de l'organisme. Enfin, nous avons exploré une éventuelle différence concernant le métabolisme du lactate dans deux populations de coureurs de 400 m d'origine ethniques différente : caucasiens et africains. L'étude 1 montre que la force maximale développée par les membres inférieurs est reliée à la vitesse moyenne soutenue sur les trois phases, constituant chronologiquement le 100 m. La raideur musculo-tendineuse est significativement corrélée à la vitesse moyenne de la seconde phase. La relation entre la vitesse moyenne sur 100 m et la concentration sanguine de lactate, obtenue dans l'étude 2, démontre que la production d'énergie, via la glycolyse anaérobie, est un facteur déterminant de la performance. De plus, il est démontré que la plus grande partie de l'énergie métabolique, nécessaire pour effectuer 100 m, provient de la glycose anaérobie. Les résultats d'une troisième étude montrent que les coureurs de demi-fonds (800 et 1500 m) possèdent une aptitude à échanger le lactate supérieure à celle des coureurs de sprint court et long (100 et 400 m), lors d'un exercice de 1 mn à 25,2 km.h-1. Dans le cadre de l'étude 4; les coureurs de 400 m caucasiens semblent obtenir une meilleure aptitude à échanger et à éliminer le lactate que leurs homologues africains.LYON1-BU.Sciences (692662101) / SudocSudocFranceF