Comparison of power and EMG during 6-s all-out cycling between young and older women     

CR Duffy  D Stewart  F Pecoraro  PE Riches  D Farina  A Macaluso 《Journal of sports sciences》2012,30(12):1311-1321

Abstract To investigate the effects of ageing on the neural control strategies governing sprint cycling on a friction-loaded cycle-ergometer, 10 older (aged 70-83yr) and 8 young (aged 19-35yr) healthy women completed seven 6-s all-out cycling trials against varying loads. Root mean square (RMS), median frequency and muscle fibre conduction velocity were determined from the vastus lateralis of the dominant limb during each pedal stroke. Peak power was 43% lower in the older group compared to the younger (p??0.05). ΔRMS from the first to the sixth second during each trial was found to increase significantly with the development of power output in both groups (p?相似文献   

Active relatives and health-related physical fitness in European adolescents: The HELENA Study     

M Martín-Matillas  FB Ortega  JR Ruiz  D Martínez-Gómez  G Vicente-Rodríguez  A Marcos  L Béghin  A Kafatos  M González-Gross  M Zaccaria  D Molnár  S De Henauw  M Sjöström  LA Moreno  MJ Castillo On Behalf Of The Helena Study 《Journal of sports sciences》2012,30(13):1329-1335

Abstract High physical fitness in childhood and adolescence is positively associated with favourable health-related outcomes. Our aim was to examine the relationship between relatives' (father, mother, brother, sister, and best friend) physical activity engagement and encouragement on adolescents' physical fitness. Adolescents were part of the HELENA study, a multi-centre study conducted in 10 cities from nine European countries in 2006-2008. Participants were 3288 adolescents (48% boys, 52% girls) aged 12.5-17.5 years with valid data on at least one of the three fitness variables studied: muscular strength (standing long jump), speed/agility (4×10 m shuttle run), and cardiorespiratory fitness (20 m shuttle run). The adolescents reported their relatives' physical activity engagement and encouragement. Analysis of covariance showed that relatives' physical activity engagement (father, mother, brother, and best friend) was positively related to cardiorespiratory fitness (P?相似文献   

The effect of warm up on single and intermittent-sprint performance     

Yaicharoen P  Wallman K  Bishop D  Morton A 《Journal of sports sciences》2012,30(8):833-840

Lack of benefit of warm up on prolonged intermittent-sprint performance has been proposed to be due to use of a pacing strategy by participants. To investigate this, twelve participants performed four cycle trials that consisted of either prolonged intermittent-sprint performance (80 min) or single-sprint performance (4 s), with or without a warm up. The first-sprint of intermittent-sprint performance was also assessed. No interaction effects (P > 0.05) were found between trials for intermittent-sprint performance for total work (J · kg(-1)), or percentage work and power decrement. Work done during the first-sprint of intermittent-sprint performance (no warm up) was less (P < 0.001) than the first-sprint of intermittent-sprint performance (warm up; effect size (ES) = 0.59) and both single-sprint trials (warm up and no warm up; ES = 0.91, 0.75, respectively). Peak power (W · kg(-1)) for single-sprint (warm up) was greater (P < 0.05) than single-sprint (no warm up), and the first-sprint of intermittent-sprint performance (warm up and no warm up). Warm up improved single-sprint performance and the first sprint of intermittent-sprint performance. Use of a pacing strategy probably resulted in similar intermittent-sprint performance between trials. These results suggest that team-sport players should perform a warm up at the start of a game or before substitution during a game.  相似文献   

The impact of task complexity on people’s mental models of MedlinePlus     

Yan Zhang^{Author Vitae} 《Information processing & management》2012,48(1):107-119

  相似文献   

Special Section: The UK Academy for Information Systems (UKAIS) 2012 Conference. Innovating Information Systems     

David Wainwright 《International Journal of Information Management》2012

  相似文献   

User-satisfaction based bandwidth allocation for transmission of multiple sources of human perceptual data     

Cheng-Chun Chang  Tien-Ying Kuo  Yi-Chung Lo  Heung-No Lee  David Askey  Zhi-Hong Mao 《Journal of The Franklin Institute》2012,349(3):879-890

In recent years, more and more point-to-point communication systems involve simultaneous transmission of multiple sources of human perceptual data over a single communication medium. For example, in a teleoperation system or a telerobotic system, streams of video, audio, and haptic data need to be sent from a field place to a remote human operator. Each type of data demands a certain range of transmission rate. This creates conflicts among these data when the available bandwidth is limited.In this paper we study the bandwidth allocation for multiple sources of human perceptual data transmitted over a rate-limited communication channel. We aim to maximize the overall user satisfaction in the data transmission, and formulate an optimization problem for the bandwidth allocation. Using either the logarithmic or exponential form of human perceptual satisfaction function, we are able to derive closed-form solutions for the optimization problem. We show that the optimal bandwidth allocation for each type of data is piecewise linear with respect to the total available bandwidth.  相似文献   

An institutional theory investigation of U.S. technology development trends since the mid-19th century     

Jason M. Pattit  S.P. Raj  David Wilemon 《Research Policy》2012,41(2):306-318

Drawing on institutional theory, we examine how institutions have influenced technology development trends in the U.S. since the mid-19th century. Based on an inductive analysis of the history of technology development and corporate R&D, we show that both formal and informal institutional rules and constraints played a role in the initial rise of markets for technology, their decline during the early-20th century, and their eventual return at the end of the 20th century. We also find that formal and informal institutions influenced the widespread adoption of in-house R&D labs during the mid-20th century. Our study integrates insights from both the economics and sociology branches of institutional theory. This perspective is particularly useful to analyze historical phenomenon and shifts in trends across long time periods.  相似文献   

The cipher of the zodiac     

Robert Fox  Charles C. Gillispie  Theresa Levitt  David Aubin  Jed Z. Buchwald  Diane Greco Josefowicz 《Metascience》2012,21(3):509-530

  相似文献   

Kinematic changes during learning the longswing on high bar     

Williams G  Irwin G  Kerwin DG  Newell KM 《Sports biomechanics / International Society of Biomechanics in Sports》2012,11(1):20-33

The purpose of this study is to provide evidence of technique changes during learning a sports-specific skill, the looped bar longswing (LLS). Thirteen male participants with no previous high bar experience took part in a training study. Kinematic data were collected using a CODA motion analysis system (200 Hz) during eight weekly testing sessions. Analyses focused on the amplitude of swing and the functional phase (FP) actions, defined by the rapid flexion to extension of the shoulders and extension to flexion of the hips as the performer passed through the lower vertical. Three groups were identified based on the number of sessions it took each participant to perform the LLS (G1: most successful, G2: intermediate, and G3: least successful). All participants were able to significantly increase swing amplitude over the training period (p < 0.05). For each participant the hip FP started significantly: later for G1, earlier for G2, and did not change for G3. Extension actions at the shoulders were dissimilar to those reported for elite gymnasts performing the longswing. The FP of the hips provides a mechanism to distinguish between the learners of different skill levels. The study has provided support for a single-subject design when investigating technique changes during learning.  相似文献   

Getting Generation Y to attend: Friends,interactivity and half-time entertainment     

David Hugh Bednall  Michael Valos  Stewart Adam  Colin McLeod 《Sport Management Review》2012,15(1):80-90

People from Generation Y, given their number and stage in the family life-cycle, represent a key emerging audience for major sports. The study focussed on the effect of friends and half time enhancements on likely attendance at matches. The sport domain was the Australian Football League (AFL), the elite Australian rules football competition. The enhancements being tested were half-time entertainments based on performers from well-known television talent shows, Australian Idol and It Takes Two. Scenarios with and without interactive participation, based on short messaging service (SMS) messages, were tested. The study used a general population sample of 909 Generation Y people in a traditional AFL market and one where AFL is not the major winter competition. Previous attendance and sport orientation were the major influences on attendance at major sports, including the AFL. Friends influenced likely attendance at a game, but no effects were found for half-time entertainments. People who attended matches with friends typically had social activities before and after the game. This suggested that one promotional strategy to expand existing markets was to find and engage the social networks of existing fans, making sport attendance a broader part of an overall social event.  相似文献