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

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   

Relationship between performance-based and laboratory tests for lower-limb muscle strength and power assessment in healthy older women

Abstract

The aim of the study was to assess the relationship between performance-based and laboratory tests for muscular strength and power assessment in older women. Thirty-two women aged 68.8 ± 2.8 years were recruited. All participants were asessed for: (a) two performance-based tests – the box-stepping test (mean 296 ± 51 J) and two-revolution maximum test (mean 7.1 ± 2 kg) performed while pedalling on a cycle ergometer; and (b) muscular function tests – maximal instantaneous peak power jumping on a force platform (mean 1528 ± 279 W); maximal voluntary contraction (MVC) during knee extension (mean 601 ± 571 N) and leg press (mean 626 ± 126 N), and leg press power (mean 483 ± 98 W) on a dynamometer. Using univariate analysis, performance-based tests were compared with laboratory muscle strength and power measurements. Muscle power correlated most strongly with the performance-based tests for both jumping and leg press power (r-values between 0.67 and 0.75; P < 0.01). The correlation with muscle strength measures ranged between 0.48 and 0.61 (P < 0.01). The proposed tests may have particular relevance in geriatric and rehabilitation environments as they represent an easy, practical, and inexpensive alternative for the assessment of muscular strength and power.     

The teacher leadership process: Attempting change within embedded systems

This embedded case study examines the leadership practices of eleven teacher leaders in three urban schools to identify how these teacher leaders attempt to change the teaching practice of their colleagues while working as professional learning community leaders and as mentors for new teachers. Using a theoretical framework integrating complex systems theory with Kotter’s (Leading change. Harvard University Press, Cambridge, 1996) eight steps for leading organizational change, we analyze the work and perspectives of individual teacher leaders, and we examine how teams of teacher leaders and principals function collectively in their efforts to lead instructional change. Our findings have implications for schools seeking to utilize teacher leadership as a reform strategy for authentic instructional improvement.     

Re-writing English Education: A Review of Robert Yagelski’s Writing as a Way of Being

Given the Cartesian influence in mainstream American education, writing instruction has come to reflect a dualistic worldview, with the writer understood as an autonomous observer/knower. As such, writing instructors have the potential to convey problematic lessons about the self as entirely separate from the world. This essay delineates a corrective to the Cartesian mindset in mainstream writing instruction: Yagelski’s ontological theory of writing as a way of being-in-the-world. In the spirit of connectedness Yagelski espouses, I consider the ways in which Yagelski’s ontological theory of writing might work in tandem with Rosenblatt’s transactional theory of reading. Together, Yagelski and Rosenblatt allow English educators to reimagine reading and writing as activities with the ethical potential to repair the rifts of a dualistic worldview, and ultimately to reimagine English education as a field that breaks the Cartesian frame.     

Relationship between performance-based and laboratory tests for lower-limb muscle strength and power assessment in healthy older women

The aim of the study was to assess the relationship between performance-based and laboratory tests for muscular strength and power assessment in older women. Thirty-two women aged 68.8 +/- 2.8 years were recruited. All participants were asessed for: (a) two performance-based tests--the box-stepping test (mean 296 +/- 51 J) and two-revolution maximum test (mean 7.1 +/- 2 kg) performed while pedalling on a cycle ergometer; and (b) muscular function tests--maximal instantaneous peak power jumping on a force platform (mean 1528 +/- 279 W); maximal voluntary contraction (MVC) during knee extension (mean 601 +/- 571 N) and leg press (mean 626 +/- 126 N), and leg press power (mean 483 +/- 98 W) on a dynamometer. Using univariate analysis, performance-based tests were compared with laboratory muscle strength and power measurements. Muscle power correlated most strongly with the performance-based tests for both jumping and leg press power (r-values between 0.67 and 0.75; P < 0.01). The correlation with muscle strength measures ranged between 0.48 and 0.61 (P < 0.01). The proposed tests may have particular relevance in geriatric and rehabilitation environments as they represent an easy, practical, and inexpensive alternative for the assessment of muscular strength and power.     

Conflict in the Dyadic Play of 3-Year-Old Children

Episodes of conflict provide a rich source of information about children's development of interactive skills. In the present study, 184 3-year-old children were observed in dyadic play and the 287 conflicts that occurred during their play were transcribed and coded. In general, children's conflicts arose in the context of ongoing play and were brief, lasting less than 15 seconds. Most disputes concerned toy possession, and almost 80% were ended by the simple withdrawal of one or the other children from the conflict. When children responded with emotional intensity to conflict, their conflicts lasted longer and were more likely to be followed by continued negative interaction. Individual difference data were available for one member of each dyad observed in play. Children rated in infancy as having difficult temperaments were found to be more intense during conflict, to spend more time in conflict, and to score higher on an index of conflict resolution competence, whereas concurrent social behavior was not related to conflict variables. Girls scored higher than boys on competence at conflict resolution, and children with better language skills spent less time in conflict. The more time children spent in nonmaternal child care up to age 3, the less likely they were to initiate conflict.