Asymmetric resting scapular posture in healthy overhead athletes

Context: Observation of the scapular posture is one of the most important components of the physical examination in overhead athletes. Postural asymmetry is typically considered to be associated with injuries. However, asymmetry in the overhead athlete's scapula may be normal due to the dominant use of the limb. Objective: To quantify the differences in resting scapular posture between the dominant and nondominant sides in 3 groups of healthy overhead athletes (baseball pitchers, volleyball players, and tennis players) using an electromagnetic tracking device. Design: Cross-sectional design. Setting: University-based biomechanics laboratory. Patients or Other Participants: A total of 43 players participated, including 15 baseball pitchers, 15 volleyball players, and 13 tennis players. All participants were healthy college-aged men. Intervention(s): Bilateral 3-dimensional scapular kinematics with the arm at rest were measured using an electromagnetic tracking device. Main Outcome Measure(s): Bilateral scapular position and orientation were measured. Between-groups and between-sides differences in each variable were analyzed using separate analyses of variance. Results: In tennis players, the scapula was more protracted on the dominant side than on the nondominant side (P , .05). In all overhead athletes, the dominant-side scapula was more internally rotated (P 5 .001) and anteriorly tilted (P 5 .001) than the nondominant-side scapula was. Conclusions: The dominant-side scapula of the overhead athletes was more internally rotated and anteriorly tilted than the nondominant-side scapula. The dominant-side scapula of the tennis players was more protracted than that on the nondominant side. Clinicians evaluating overhead athletes need to recognize that scapular posture asymmetry in unilateral overhead athletes may be normal. Our results emphasize the importance of the baseline evaluation in this population in order to accurately assess pathologic change in bilateral scapular positions and orientations after injury

Operation and performance of the ATLAS semiconductor tracker in LHC Run 2

The semiconductor tracker (SCT) is one of the tracking systems for charged particles in the ATLAS detector. It consists of 4088 silicon strip sensor modules. During Run 2 (2015–2018) the Large Hadron Collider delivered an integrated luminosity of 156 fb-1 to the ATLAS experiment at a centre-of-mass proton-proton collision energy of 13 TeV. The instantaneous luminosity and pile-up conditions were far in excess of those assumed in the original design of the SCT detector. Due to improvements to the data acquisition system, the SCT operated stably throughout Run 2. It was available for 99.9% of the integrated luminosity and achieved a data-quality efficiency of 99.85%. Detailed studies have been made of the leakage current in SCT modules and the evolution of the full depletion voltage, which are used to study the impact of radiation damage to the modules

THE RELATIONSHIP BETWEEN FORCE PLATFORM MEASURES AND TOTAL BODY CENTER OF MASS THE RELATIONSHIP BETWEEN FORCE PLATFORM MEASURES AND TOTAL BODY CENTER OF MASS

The ability of a person to maintain stable posture is essential for activities of daily living. Research in this field has evolved to include sensitive assessment technology including force platforms and 3-dimensional kinematic motion analysis systems. Although many studies have investigated postural stability under the auspice of posturography and the use of force platforms, relatively few have incorporated kinematic motion analysis techniques. Furthermore, of the studies that have utilized a multivariate research model, none have sought to identify the relationship between force platform measures including both the variation of movement of the xand y-coordinates of the center of pressure (COP), and the 3-dimensional coordinates of the total body center of mass (COM). This study used a descriptive design to evaluate the relationship between force platform measures and the kinematic measures dealing with the total body COM in 14 healthy participants (height = 1.70 ± 0.09 m, mass = 67.7 ± 9.9 kg; age = 24.9 ± 3.8 yrs). Intraclass correlations (ICC) and standard error of measurements (SEM) were determined for common variables of interest used in standard posturography models. The results suggest that the variation of the excursion of the COP coordinates best represent the variation of the total body COM in the x-and y-directions. There was a force platform measure that correlated significantly with the vertical component of total body COM in only 3 of the 8 conditions. The ICC values obtained when analyzing individual conditions revealed that the variation in the force measurements were much more reliable than those representing the variation in movement of the iv COP, suggesting a need for the development of higher order methods of modeling 3-dimensional COM information from force platforms.