Age- and gender-related development of stretch shortening cycle during a sub-maximal hopping task

The aim of this study was to analyse the effects of age and gender (and their interaction) on a stretch shortening cycle solicited during a hopping task. For this aim, 147 girls and 148 boys aged 11 to 20 years, who were enrolled in middle school or secondary school with no experience in sport activity, or training less than three times per week, performed 3 75 hops in place. Leg-stiffness, jump-height and reactive-strength indices were assessed using an accelerometer (Myotest). The participants were selected in order to form five age groups: 11 12, 13-14, 15-16, 17-18 and 19-20 years. Regression analysis between force and centre of mass displacement revealed spring-mass behaviour for all groups (r(2)=.73-.89), meaning that beginning at the age of 11 years, children are able to perform complex inter-muscular coordination of the lower limbs, revealing efficient neural control early in childhood. Leg stiffness increased from 24.7 \ub1 10.6 kN \ub7 m(-1) at 11-12 years to 44.1 \ub1 14 kN \ub7 m(-1) in boys, with a small increase until 16 years (+17%) and a large increase between 17 and 20 years (+32.7%). In girls, leg stiffness increased from 26.6 \ub1 9 kN \ub7 m(-1) at 11-12 years to 39.4 \ub1 10.9 kN \ub7 m(-1) at 19-20 years, with a curious decrease in leg stiffness at 17-18 years, probably due to an increase in the percentage of fat at this age (25%). While no gender effect was found, the reactive-strength index revealed that, from 15-16 years onward, boys were better able to produce high levels of force in a shorter time than girls. The age of 15-16 years is a threshold of maturity and gender differentiation, where the boys investigated are more efficient in the stretch shortening cycle

Statins but Not Aspirin Reduce Thrombotic Risk Assessed by Thrombin Generation in Diabetic Patients without Cardiovascular Events: The RATIONAL Trial

The systematic use of aspirin and statins in patients with diabetes and no previous cardiovascular events is controversial. We sought to assess the effects of aspirin and statins on the thrombotic risk assessed by thrombin generation (TG) among patients with type II diabetes mellitus and no previous cardiovascular events.Prospective, randomized, open, blinded to events evaluation, controlled, 2×2 factorial clinical trial including 30 patients randomly allocated to aspirin 100 mg/d, atorvastatin 40 mg/d, both or none. Outcome measurements included changes in TG levels after treatment (8 to 10 weeks), assessed by a calibrated automated thrombogram. At baseline all groups had similar clinical and biochemical profiles, including TG levels. There was no interaction between aspirin and atorvastatin. Atorvastatin significantly reduced TG measured as peak TG with saline (85.09±55.34 nmol vs 153.26±75.55 nmol for atorvastatin and control groups, respectively; p = 0.018). On the other hand, aspirin had no effect on TG (121.51±81.83 nmol vs 116.85±67.66 nmol, for aspirin and control groups, respectively; p = 0.716). The effects of treatments on measurements of TG using other agonists were consistent.While waiting for data from ongoing large clinical randomized trials to definitively outline the role of aspirin in primary prevention, our study shows that among diabetic patients without previous vascular events, statins but not aspirin reduce thrombotic risk assessed by TG.ClinicalTrials.gov NCT00793754

Beyond in-phase and anti-phase coordination in a model of joint action

In 1985, Haken, Kelso and Bunz proposed a system of coupled nonlinear oscillators as a model of rhythmic movement patterns in human bimanual coordination. Since then, the Haken–Kelso–Bunz (HKB) model has become a modelling paradigm applied extensively in all areas of movement science, including interpersonal motor coordination. However, all previous studies have followed a line of analysis based on slowly varying amplitudes and rotating wave approximations. These approximations lead to a reduced system, consisting of a single differential equation representing the evolution of the relative phase of the two coupled oscillators: the HKB model of the relative phase. Here we take a different approach and systematically investigate the behaviour of the HKB model in the full four-dimensional state space and for general coupling strengths. We perform detailed numerical bifurcation analyses and reveal that the HKB model supports previously unreported dynamical regimes as well as bistability between a variety of coordination patterns. Furthermore, we identify the stability boundaries of distinct coordination regimes in the model and discuss the applicability of our findings to interpersonal coordination and other joint action tasks

A New Direction to Athletic Performance: Understanding the Acute and Longitudinal Responses to Backward Running

Backward running (BR) is a form of locomotion that occurs in short bursts during many overground field and court sports. It has also traditionally been used in clinical settings as a method to rehabilitate lower body injuries. Comparisons between BR and forward running (FR) have led to the discovery that both may be generated by the same neural circuitry. Comparisons of the acute responses to FR reveal that BR is characterised by a smaller ratio of braking to propulsive forces, increased step frequency, decreased step length, increased muscle activity and reliance on isometric and concentric muscle actions. These biomechanical differences have been critical in informing recent scientific explorations which have discovered that BR can be used as a method for reducing injury and improving a variety of physical attributes deemed advantageous to sports performance. This includes improved lower body strength and power, decreased injury prevalence and improvements in change of direction performance following BR training. The current findings from research help improve our understanding of BR biomechanics and provide evidence which supports BR as a useful method to improve athlete performance. However, further acute and longitudinal research is needed to better understand the utility of BR in athletic performance programs

Erratum: The solar orbiter radio and plasma waves (RPW) instrument (Astronomy and Astrophysics (2020) 642 (A12) DOI: 10.1051/0004-6361/201936214)

The erratum concerns Fig. 9 entitled "Antenna radio-electrical properties" for which some of the parameters are not correct. The new figure with new parameters is provided in Fig. 1 of this corrigendum. Fig. 1. Corrected Antenna radio-electrical properties. (Figure Presented)

How to prevent COVID-19 by means of a daily micronutrition protocol? An overview

Aim. Coronavirus, also known as COVID-19, has officially been declared as a pandemic, and the world now has to manage this pandemic disease as a major public health issue at different levels, not only from a political aspect, but also from an individual aspect at the lower end of the scale. The goal of this paper is to focus on how individuals could optimize their health, and particularly their immune systems, to reduce the risk of respiratory tract infections by means of a daily micronutrition strategy. Material and Methods. A narrative review was conducted on 85 articles evaluating the mechanisms which allow vitamin D, vitamin C and Zinc to lower viral replication rates and reduce pro-inflammatory cytokine storm. Furthermore, we focus on high-risk populations with the prism of deficiency of these vitamins and this mineral. Results. According to literature, it seems that Zinc and vitamins C and D, particularly when taken as supplementation at an early stage, could be clinically useful micronutrients as adjuvant therapies in the prevention of deficiency amplification in COVID-19 unaffected and at-risk populations, and/or in the treatment of severe forms in affected patients. Conclusion. Further randomized control trials through the use of genomics and metabolomic techniques are needed in order to understand the role of these micronutrients in the treatment of severe forms of the COVID-19 disease in different types of at-risk populations

La régulation de la raideur au cours du saut

Les sauts sont des habiletés complexes qui requièrent des stratégies multiples de contrôle moteur. Les modèles masse ressort permettent de comprendre les modes de régulation dans des tâches de saut et de réduire la complexité de ce contrôle. Le but de cette thèse est de savoir comment la raideur mécanique participe à la régulation du comportement du sujet et s'il existe dans l'impulsion une signature mécanique liée à l'appartenance sportive. Dans une expérience de transition course-saut appel un pied, réalisée avec des experts en saut, nous avons constaté qu'une raideur minimale était nécessaire pour sauter haut. Cependant, aucune corrélation significative n'a été trouvée entre raideur et performance verticale. Lors de saut de contre-haut, nous avons montré qu'il était possible de réguler la raideur en donnant des consignes sur la flexion maximale du genou. Ces résultats soutiennent l'idée qu'il est possible de sauter haut avec des valeurs de raideur différentes. Deux autres expérimentations montrent l'existence d'une signature de l'appartenance à une catégorie sportive, visible à travers les paramètres mécaniques de l'impulsion, lors de sauts un pied et avec contre-mouvement. Ainsi, ces sauts peuvent être capturés par une composante temporelle et une composante force. Le modèle trouvé permet de différencier les athlètes en fonction de leur appartenance sportive (volley-ball, basket-ball, hand-ball, Fosbury-flop et novices).Jumping high necessitates complex motor skill, who requires different strategies of motor control. Mass-spring models are usually used to describe human or animal locomotion, like jumping tasks. Two main questions are asked: Is leg stiffness used to regulate human behavior ? Does a signature between athletes performing in varied sports exist? In an experiment on running single-leg jump performed by different athletes in varied sports, we have shown that a minimal value of leg stiffness is necessary to jump high, but there is no significant correlation between stiffness and vertical jump performance. During drop jump, it is possible to regulate leg stiffness through instructions about the knee flexion. These results confirm the idea that jumping high could be performed with different levels of stiffness. A signature of athletes performing in varied sports has been confirmed during running single-leg jump and counter-movement jump. These jumps could be captured by a temporal and a force component and allow to differentiate athletes from their sport origin (volley-ball, basket-ball, hand-ball, Fosbury-flop et novices).ORSAY-PARIS 11-BU Sciences (914712101) / SudocORSAY-PARIS11-Bib. STAPS (914712103) / SudocSudocFranceF

Upper-limb power test in rock-climbing

The goal of the present study was to validate a new ecological power-test on athletes of different levels and to assess rock climbers' profiles (boulderers vs. route climbers). 34 athletes divided into novice, skilled and elite groups performed the arm-jump board test (AJ). Power, time, velocity, and efficiency index were recorded. Validity was assessed by comparing the distance with the value extracted from the accelerometer (500Hz) and the reliability of intra- and inter-session scores. Moreover, a principal component analysis (PCA) was used to assess the climbers' profiles. The AJ test was quite valid, showing a low systematic bias of -0.88cm (-1.25%) and low limits of agreement (<6%), and reliable (Intra-class correlation coefficient=0.98 and CV<5%), and was able to distinguish between the 3 samples (p<0.0001). There was a good correlation between relative upper-limb power (r=0.70; p<0.01) and the AJ score. Moreover, the PCA revealed an explosive profile for boulderers and either a weak and quick or slow profile for route climbers, revealing a biomechanical signature of the sub-discipline. The AJ test provides excellent absolute and relative reliabilities for climbing, and can effectively distinguish between climbing athletes of different competitive levels. Thus, the AJ may be suitable for field assessment of upper limb strength in climbing practitioners