A mathematical model for power output in rowing on an ergometer

A mathematical model relating power output of rower to stroke rate on an ergometer (the Concept II Indoor Rower TM, Model C) is studied. The model is used to analyse the ergometer performance of a particular rower. It is determined that he can be more efficient (i.e. decrease power output while maintaining fixed velocity) by decreasing stroke rate, but at the expense of increasing force during the drive. It is also shown that he can be more efficient by increasing the drag factor (using higher vent setting) without increasing force. Dependence of power output on rowing style (the shape of the force curve) is also examined. It is shown that variation of force during the drive has little effect on efficiency, but efficiency is reduced by asymmetry of the force curve that favours the legs.     

Index to Volume XLI

Other Index

Index to Volume XLI     

Student activity levels, lesson context, and teacher behavior during middle school physical education

There is little research on students' engagement in physical activity in middle school physical education (PE). We observed student activity, lesson context, and teacher behavior in 430 PE lessons taught by 126 teachers in 24 schools. Variables were analyzed by mixed-model nested analyses of covariance. Boys were more active than girls overall and during skill drills, game play, and free play. Student activity varied by lesson context, with fitness activities producing the most activity. Class size was negatively associated with student activity. Daily PE contributed a weekly total of 25 min of vigorous activity and 83 min of moderate-to-vigorous activity--much less than national objectives. Results suggest that numerous opportunities exist for increasing student physical activity during middle school PE.     

Culturally responsive computing: a theory revisited

Despite multiple efforts and considerable funding, historically marginalized groups (e.g., racial minorities and women) continue not to enter or persist in the most lucrative of fields – technology. Understanding the potency of culturally responsive teaching (CRT), some technology-enrichment programs modified CRP principles to establish a culturally responsive computing (CRC) experience for disenfranchised groups. We draw from our respective praxes developing two such initiatives and reconceptualize CRC as a heuristic. In this theoretical article, we offer a more nuanced vision of CRC considering intersectionality, innovations, and technosocial activism. Implications for the newly defined tenets consider programmatic, theoretical, and methodological concerns.     

Lifesource XL-18 pedometer for measuring steps under controlled and free-living conditions

The primary aim was to examine the criterion and construct validity and test–retest reliability of the Lifesource XL-18 pedometer (A&D Medical, Toronto, ON, Canada) for measuring steps under controlled and free-living activities. The influence of body mass index, waist size and walking speed on the criterion validity of XL-18 was also explored. Forty adults (35–74 years) performed a 6-min walk test in the controlled condition, and the criterion validity of XL-18 was assessed by comparing it to steps counted manually. Thirty-five adults participated in the free-living condition and the construct validity of XL-18 was assessed by comparing it to Yamax SW-200 (YAMAX Health & Sports, Inc., San Antonio, TX, USA). During the controlled condition, XL-18 did not significantly differ from criterion (P > 0.05) and no systematic error was found using Bland–Altman analysis. The accuracy of XL-18 decreased with slower walking speed (P = 0.001). During the free-living condition, Bland–Altman analysis revealed that XL-18 overestimated daily steps by 327 ± 118 than Yamax (P = 0.004). However, the absolute percent error (APE) (6.5 ± 0.58%) was still within an acceptable range. XL-18 did not differ statistically between pant pockets. XL-18 is suitable for measuring steps in controlled and free-living conditions. However, caution may be required when interpreting the steps recorded under slower speeds and free-living conditions.     

Undisclosed Flexibility in Computing and Reporting Structural Equation Models in Communication Science

The use of structural equation modeling (SEM) in communication research has become increasingly popular in recent years, with SEM being commonly used as the primary method of data analysis in studies published within the field’s journals. However, despite its widespread use, there are persistent misapplications of SEM in published empirical studies in the communication sciences. Of these types of misuse, the most troubling are those related to the exploitation of flexibilities in data collection and analysis. Given the number of decisions that must be made when analyzing and reporting structural equation models, decisions which often remain undisclosed, the potential for researchers to exploit flexibilities in SEM research is high. To assess the extent of this problem, as well as the more longstanding types of misuse (i.e., omission of information and disclosed “bad practice”) identified by prior studies, we undertake a methodical review of studies employing structural equation modeling within major journals in the field of communication between the years 2007 and 2011. Articles were coded on the characteristics of the sample, characteristics of the model tested, as well as for various potential problems that we defined a priori. The most serious issues are identified, and recommendations for future standards in SEM research are suggested.