Reliability and validity of a new double poling ergometer for cross-country skiers

Thirty-eight competitive cross-country skiers were divided into three groups to assess the reliability and validity of a new double poling ergometer. Group A (n = 22) performed two maximal 60-s tests, Group B (n = 8) repeated peak oxygen uptake tests on the double poling ergometer, and Group C (n = 8) performed a maximal 6-min test on the double poling ergometer and a double poling time-trial on snow. The correlation between the power calculated at the flywheel and the power applied at the base of the poles was r = 0.99 (P < 0.05). The power at the poles was 50-70% higher than that at the flywheel. There was a high test-retest reliability in the two 60-s power output tests (coefficient of variation = 3.0%) and no significant difference in peak oxygen uptake in the two 6-min all-out tests (coefficient of variation = 2.4%). There was a strong correlation between the absolute (W) and relative power (W x kg(-1)) output in the 6-min double poling ergometer test and the double poling performance on snow (r = 0.86 and 0.89 respectively; both P < 0.05). In conclusion, our results show that the double poling ergometer has both high reliability and validity. However, the power calculated at the flywheel underestimated the total power produced and needs to be corrected for in ergonomic estimations.     

The effect of self‐directed work teams on work ethic

This study examined the work ethic of manufacturing machine operators between self‐directed work teams and traditional work groups using four work ethic subscales: dependable, considerate, ambitious, and cooperative (Dawson, 1999 ; Petty, 1991 ). Differences in measured work ethic scores were also compared across six demographic variables: age, gender, level of education, years of full‐time work experience, years of experience as a supervisor, and work shift preference. Findings showed that there were significant differences in the work ethic between those two team structures and age groups. Implications for future research were presented.     

A new device for measuring ski running surface force and pressure profiles

The pressure/force acting between the running surface of a ski and the snow may indirectly change glide friction. Thus, measuring the pressure/force distribution may be important for a deeper understanding of glide in skiing. The present aim was to construct a device that allowed the pressure/force underneath the ski running surface (SRS) to be recorded. Pressure sensors were attached on top of a platform. Sheets of different materials were used to improve the interaction between the SRS and the sensors. Possible functions of the device are demonstrated in three applications that emphasized comparison of force distribution underneath skis selected for similarity, force distribution under both skis and a single ski as well as backward weight distribution. The results show that the device with the pressure sensors mapped pressure/force distribution underneath the skis in the applications presented, and the system can thus be a useful tool for further optimizing e.g., ski designs.     

Skiing

The purpose of the investigation was to study the relationship between thrust phase duration, ground reaction force, velocity increase after pole thrust and pole angles versus pole length during double poling in roller skiing. Seven male regional elite cross‐country skiers volunteered as subjects for the study. The subjects performed a maximal double pole thrust on roller skis with each of the three different pole lengths: ‘short’, self‐selected (normal) and ‘long’. The short and long poles were 7.5 cm shorter and 7.5 cm longer than the self‐selected pole length. The subjects made seven maximal pole thrusts with each pole length, which were randomly selected during 21 trials. For each trial the subjects accelerated from a 1.2 m high downhill slope attaining a speed of 3.92 m.s^‐1 before making a maximal double pole thrust on a force plate placed at the bottom of the slope. The vertical (F_z), anterior‐posterior (F_y) and medio‐lateral (F_x) reaction forces of the left pole were measured by the force plate. The positions of the pole were recorded in 3‐D by an opto‐electronic system. Thrust phase duration, impulse, mean force, velocity increase after pole thrust and pole angles were calculated from the recorded data. Double poling with long poles produced a significantly larger propulsive anterior‐posterior reaction force impulse and velocity increase than normal (p < .05) and short poles (p < .05). This was in spite of a larger mean anterior‐posterior reaction force being produced with short poles. Thus, thrust phase duration was a primary factor in determining propulsive anterior‐posterior impulse. For the practitioner, the results can be useful in the selection of pole length when the aim is to increase thrust phase duration, anterior‐posterior force impulse and velocity.     

Acute effects of whole-body vibration on running gait in marathon runners

Abstract

The aim of this study was to investigate the effects of a single bout of whole-body vibration (WBV) on running gait. The running kinematic of sixteen male marathon runners was assessed on a treadmill at iso-efficiency speed after 10 min of WBV and SHAM (i.e. no WBV) conditions. A high-speed camera (210 Hz) was used for the video analysis and heart rate (HR) was also monitored. The following parameters were investigated: step length (SL), flight time (FT), step frequency (SF), contact time (CT), HR and the internal work (W_INT). Full-within one-way analysis of variance (ANOVA) of the randomised crossover design indicated that when compared to SHAM conditions, WBV decreased the SL and the FT by ~4% (P < 0.0001) and ~7.2% (P < 0.001), respectively, and increased the SF ~4% (P < 0.0001) while the CT was not changed. This effect occurred during the first minute of running: the SL decreased ~3.5% (P < 0.001) and SF increased ~3.3% (P < 0.001). During the second minute the SL decreased ~1.2% (P = 0.017) and the SF increased ~1.1% (P = 0.02). From the third minute onwards, there was a return to the pre-vibration condition. The W_INT was increased by ~4% (P < 0.0001) during the WBV condition. Ten minutes of WBV produced a significant alteration of the running kinematics during the first minutes post exposure. These results provide insights on the effects of WBV on the central components controlling muscle function.     

Democracy Plaza: A Campus Space for Civic Engagement

This article examines “Democracy Plaza,” a campus space dedicated to written and spoken communication about issues of public concern. The Plaza gives students opportunities to become civically engaged through self-expression and the exchange of ideas. A series of chalkboards on the Plaza allows them to write their thoughts and read the comments of others, and events where students can speak and deliberate about important civic matters are hosted in this space. This article discusses the concept of Democracy Plaza and its development, maintenance, and utilization as a campus space for civic engagement. Johnny Goldfinger is an Assistant Professor of Political Science at Indiana University–Purdue University Indianapolis. He received a B.S.Ch.E. and B.A. from the University of South Alabama, the M.A. in political science from the University of New Orleans, and the Ph.D. in political science from Duke University. His research interests include political deliberation, democratic decision-making, and civic engagement.     

The role of pragmatic arguments in computer ethics

The purpose of this paper is to stress the importance of pragmatic arguments if we are to reach overlapping consensuses across cultural and disciplinary borders. An analytical distinction is made between, on the one hand, arguments based on socio-political or philosophical presuppositions, and on the other hand, pragmatic arguments. The latter are (as far as possible) detached from culture-specific or disciplinary presuppositions. I will mainly focus on the issue of regulation and surveillance on the Internet, and put forward a selection of pragmatic arguments for why widespread regulation and surveillance ought to be avoided. These arguments are intended to reach the same conclusion as arguments that are based on socio-political and philosophical presuppositions, with the aim of creating overlapping consensuses.     

Teaching as goal-less and reflective design: a conversation with Herbert A. Simon and Donald Schön

This paper examines Donald Schön’s critique of Herbert Simon’s ‘science of design’ to determine whether later developments in Simon’s thought – particularly, his theories of ‘bounded rationality’ and ‘goal-less designing’ – can contribute to an appreciation of Schön’s notion of reflective practice. The paper then argues, that viewed through the optic of ‘assessment for learning,’ teaching may be conceived as ‘goal-less and reflective design,’ and the practice thereof may lead to more effective teaching.     

血泪之路

一个真实的故事:一个切诺基族(北美印第安人中易洛魁人的一支)男孩伤心欲绝地走过美国历史上的一段黑暗时期。