Multicenter trial of motion analysis for injury risk prediction: lessons learned from prospective longitudinal large cohort combined biomechanical - epidemiological studies

Our biodynamics laboratory group has conducted large cohort biomechanical-epidemiological studies targeted at identifying the complex interactions among biomechanical, biological, hormonal, and psychosocial factors that lead to increased risk of anterior cruciate ligament (ACL) injuries. The findings from our studies have revealed highly sensitive and specific predictors for ACL injury. Despite the high incidence of ACL injuries among young athletes, larger cohorts are needed to reveal the underlying mechanistic causes of increased risk for ACL injury. In the current study, we have outlined key factors that contribute to the overall success of multicenter, biomechanical-epidemiological investigations designed to test a larger number of athletes who otherwise could not be recruited, screened, or tested at a single institution. Twenty-five female volleyball players were recruited from a single high school team and tested at three biodynamics laboratories. All athletes underwent three-dimensional motion capture analysis of a drop vertical jump task. Kinematic and kinetic variables were compared within and among laboratories. Reliability of peak kinematic variables was consistently rated good-to-excellent. Reliability of peak kinetic variables was consistently rated goodto-excellent within sites, but greater variability was observed between sites. Variables measured in the sagittal plane were typically more reliable than variables measured in the coronal and transverse planes. This study documents the reliability of biomechanical variables that are key to identification of ACL injury mechanisms and of athletes at high risk. These findings indicate the feasibility of executing multicenter, biomechanical investigations that can yield more robust, reliable, and generalizable findings across larger cohorts of athletes.     

High‐affinity copper block of GABAA receptor‐mediated currents in acutely isolated cerebellar Purkinje cells of the rat

The actions of Cu²⁺ ions on GABA_A receptor-mediated currents in acutely isolated Purkinje cells from rat cerebellum were studied using the whole-cell patch-clamp technique and a rapid perfusion system. Bath application of Cu²⁺ reduced currents induced by 2 μm γ-aminobutyric acid (GABA) in a concentration-dependent manner with an IC₅₀ of 35 n m . The Cu²⁺-induced block of GABA responses was not voltage-dependent. Increasing the GABA concentration (from 2 to 50 μm ) decreased the blocking effect of Cu²⁺. Dose–response analysis for activation of GABA_A receptors revealed a twofold decrease in apparent affinity for GABA in the presence of 0.1 μm Cu²⁺. Recovery from the block required several minutes after removal of Cu²⁺ from the medium. The block was removed by histidine, which preferentially forms complexes with Cu²⁺, or by other chelating substances. Application of 10 μm histidine immediately before application of 2 μm GABA completely relieved the block of GABA responses produced by 0.1 μm Cu²⁺. The effect of histidine was concentration-dependent with an EC₅₀ of 0.75 μm . The results demonstrate that Cu²⁺ is a potent inhibitor of GABA-evoked responses in rat Purkinje cells. Copper may be an endogenous synaptic modulating factor. Cu²⁺ toxicity, notably in Wilson’s disease, could result to some extent from chronic GABA_A receptor blockade.     

Jump linear quadratic Gaussian problem for a class of nonhomogeneous Markov jump linear systems

This paper concerns with the jump linear quadratic Gaussian problem for a class of nonhomogeneous Markov jump linear systems (MJLSs) in the presence of process and observation noise. By assuming that mode transition rate matrices (MTRMs) are piecewise homogeneous whose variation is subjected to a high‐level Markov process, two Markov processes are proposed to model the characteristics of nonhomogeneous MJLSs: the variation of system mode is governed by a low‐level Markov process, while the variation of MTRM is governed by a high‐level one. Based on this model, a mode‐MTRM‐based optimal filter is firstly given where filter gain can be obtained via coupled Riccati equations. Secondly, we extend the separation principle of the linear quadratic problem to the nonhomogeneous MJLSs case. An optimal controller is then designed to minimize the quadratic system cost. Finally, a potential application in solar boiler system is given to illustrate the developed theoretical methods. Copyright © 2016 John Wiley & Sons, Ltd.     

Efficacy of depth jumps to elicit a post-activation performance enhancement in junior endurance runners

Objectives

To determine the effect of performing depth jumps (DJ) pre-exercise on running economy (RE) and time to exhaustion (TTE) at the speed associated with maximal oxygen uptake (s$\dot{V}$O_2max) in a group of high-performing junior middle-distance runners.

Aptitude physique et psychologique pour la reprise du sport après reconstruction du ligament croisé antérieur du genou : score ACL-RSI et tests fonctionnels

Background

For the patient returning to sport after injury, physical and psychological aptitude are crucial elements: premature return is a risk factor for new injury. The Anterior-Cruciate-Ligament Return-to-Sport-After-Injury (ACL-RSI) scale can be used to quantify the impact of psychological factors affecting a patient's aptitude for return-to-sport.

Global changes in anaerobic fitness test performance of children and adolescents (1958-2003)

AIM: To quantify the global changes in anaerobic fitness (operationalized as power and speed test performance) of children and adolescents. METHODS: Following an extensive review of the literature, 32 studies examining secular changes in power and speed test performance of children and adolescents were analysed. Performance changes were calculated at the country x age x sex x test level using weighted least-squares regression, and were expressed as a percentage of the weighted mean value for all data points in the regression. Negative values indicated performance declines, and positive values indicated improvements. RESULTS: Changes in power (n=20 802 925) and speed (n=28 320 308) test performance were calculated for 6-19 year olds from 27 countries and five geographical regions, for the period 1958-2003. Overall, power and speed test performances improved at +0.03% and +0.04% per annum, respectively. Performance changes were remarkably similar for boys and girls, and children and adolescents, and somewhat similar for different geographical regions, and high and low income economies. The pattern of change was reasonably consistent over time. CONCLUSION: The relative stability in anaerobic fitness test performances in recent decades could be due to the negating effects of increases in fat mass and fat-free mass on anaerobic performance.     

The increase in physical performance and gain in lean and fat mass occur in prepubertal children independent of mode of school transportation. One year data from the prospective controlled Pediatric Osteoporosis Prevention (POP) Study

Background

The aim of this 12-month study in pre-pubertal children was to evaluate the effect of school transportation on gain in lean and fat mass, muscle strength and physical performance.

Methods

Ninety-seven girls and 133 boys aged 7-9 years from the Malmö Pediatric Osteoporosis Prevention Study were included. Regional lean and fat mass were assessed by dual energy X-ray absorptiometry, isokinetic peak torque of knee extensors and flexors by a computerised dynamometer and physical performance by vertical jump height. Level of physical activity was assessed by accelerometers. The 12-month changes in children who walked or cycled to school were compared with changes in those who travelled by bus or car.

Results

There were no differences in baseline or annual changes in lean or fat mass gain, muscle strength or physical performance between the two groups. All children reached the internationally recommended level of 60 minutes per day of moderate or high physical activity by accelerometers.

Conclusion

The choice of school transportation in pre-pubertal children seems not to influence the gain in lean and fat mass, muscle strength or functional ability, probably as the everyday physical activity is so high that the mode of school transportation contributes little to the total level of activity.