45 research outputs found
Are tibial angles measured with inertial sensors useful surrogates for frontal plane projection angles using 2-dimensional video analysis during single leg squat tasks? A reliability and agreement analysis in elite football (soccer) players
During single leg squats (SLS), tibial angle (TA) quantification using inertial measurement units (IMU) may offer
a practical alternative to frontal plane projection angle (FPPA) measurement using 2-dimensional (2D) video
analysis. This study determined: (i) the reliability of IMUs and 2D video analysis for TA measurement, and 2D
video analysis for FPPA measurement; (ii) the agreement between IMU TA and both 2D video TA and FPPA
measurements during single leg squats in elite footballers. 18 players were tested on consecutive days. Absolute
TA (ATA) and relative TA (RTA) were measured with IMUs. ATA and FPPA were measured concurrently using
2D video analysis. Within-session reliability for all measurements varied across days (intraclass correlation
coefficient (ICC) range=0.27â0.83, standard error of measurement (SEM) range=2.12â6.23°, minimal detectable
change (MDC) range=5.87â17.26°). Between-sessions, ATA reliability was good for both systems
(ICCs=0.70â0.74, SEMs=1.64â7.53°, MDCs=4.55â7.01°), while IMU RTA and 2D FPPA reliability ranged
from poor to good (ICCs=0.39â0.72, SEMs=2.60â5.99°, MDCs=7.20â16.61°). All limits of agreement exceeded
a 5° acceptability threshold. Both systems were reliable for between-session ATA, although agreement
was poor. IMU RTA and 2D video FPPA reliability was variable. For SLS assessment, IMU derived TAs are not
useful surrogates for 2D video FPPA measures in this population
Impact Factor: outdated artefact or stepping-stone to journal certification?
A review of Garfield's journal impact factor and its specific implementation
as the Thomson Reuters Impact Factor reveals several weaknesses in this
commonly-used indicator of journal standing. Key limitations include the
mismatch between citing and cited documents, the deceptive display of three
decimals that belies the real precision, and the absence of confidence
intervals. These are minor issues that are easily amended and should be
corrected, but more substantive improvements are needed. There are indications
that the scientific community seeks and needs better certification of journal
procedures to improve the quality of published science. Comprehensive
certification of editorial and review procedures could help ensure adequate
procedures to detect duplicate and fraudulent submissions.Comment: 25 pages, 12 figures, 6 table
Spatial and Seasonal Distribution of American Whaling and Whales in the Age of Sail
American whalemen sailed out of ports on the east coast of the United States and in California from the 18th to early 20th centuries, searching for whales throughout the worldâs oceans. From an initial focus on sperm whales (Physeter macrocephalus) and right whales (Eubalaena spp.), the array of targeted whales expanded to include bowhead whales (Balaena mysticetus), humpback whales (Megaptera novaeangliae), and gray whales (Eschrichtius robustus). Extensive records of American whaling in the form of daily entries in whaling voyage logbooks contain a great deal of information about where and when the whalemen found whales. We plotted daily locations where the several species of whales were observed, both those caught and those sighted but not caught, on world maps to illustrate the spatial and temporal distribution of both American whaling activity and the whales. The patterns shown on the maps provide the basis for various inferences concerning the historical distribution of the target whales prior to and during this episode of global whaling
Adaptations in antagonist co-activation: Role in the repeated-bout effect
Eccentric exercise results in an adaptation which attenuates muscle damage from subsequent exerciseâtermed the ârepeated-bout effect (RBE).â Purpose: Study examined antagonist co-activation and motor-unit recruitment strategy, assessed via dEMG, concomitant to the RBE. Methods: Nine participants performed 5 sub-maximal isometric trapezoid (ramp-up, hold, ramp-down) contractions at force levels corresponding to 50% and 80% of maximal isometric strength (MVC). Surface EMG signals of the biceps brachii were decomposed into individual motor-unit action potential trains. The relationship between mean firing rate (MFR) of each motor-unit and its recruitment threshold (RT) was examined using linear regression. Eccentric exercise was then performed until biceps brachii MVC had decreased by ~40%. Surface EMG of the biceps and triceps were collected during eccentric exercise. MVC, range-of-motion (ROM), and delayed onset muscle soreness (DOMS) were measured 24-hours, 72-hours, and 1-week following eccentric exercise. Three weeks later all procedures were repeated. Results: Changes in MVC (-32±14% vs -25±10%; p = 0.034), ROM (-11% vs 6%; p = 0.01), and DOMS (31.0±19mm vs 19±12mm; p = 0.015) were attenuated following the second bout of exercise. Triceps EMG was reduced (16.8±9.5% vs. 12.6±7.2%; p = 0.03) during the second bout of eccentric exercise. The slope (-0.60±0.13 vs -0.70±0.18; p = 0.029) and y-intercept (46.5±8.3 vs 53.3±8.8; p = 0.020) of the MFR vs. RT relationship was altered during contractions at 80% of MVC prior to the second bout of eccentric exercise. No changes were observed at 50% of MVC. Conclusion: A reduction in antagonist co-activation during the second bout of eccentric exercise suggests less total force was required to move an identical external load. This finding is supported by the increased negative slope coefficient and an increased y-intercept of the linear relationship between RT and MFR.Funded by University of Oklahoma Graduate College Robberson Grant.Ye
Ex-post Performance Implications of Divergence of Managersâ Perceptions of âDistanceâ From âRealityâ in International Business
Despite much research on âdistanceâ, little attention has been paid to the effect of divergence of managersâ perceptions of distance from reality (i.e. distance divergence) and its implications for firm performance. This knowledge is highly important since managerial perceptions of the firmâs environment do not always coincide with the actual environmental characteristics. Consequently, strategies based on inaccurate data may result in erroneous forecasts, missed opportunities and business failure. Using survey data from senior managers of Swedish exporters and corresponding objective data, this study is a first attempt to explore the ex-post performance implications of âdistance divergenceâ when expanding into foreign markets. Our results demonstrate that the larger the divergence between managersâ perceptions of cultural distance and corresponding âobjectiveâ distance, the lower the performance expressed in companiesâ sales. However, over/underestimation of cultural distance does not have differential effects on firm performance.âStiftelsen Olle Hakelius Stipendiefondâ, Grant no: 1165001