Biomechanical pole and leg characteristics during uphill diagonal roller skiing

Diagonal skiing as a major classical technique has hardly been investigated over the last two decades, although technique and racing velocities have developed substantially. The aims of the present study were to 1) analyse pole and leg kinetics and kinematics during submaximal uphill diagonal roller skiing and 2) identify biomechanical factors related to performance. Twelve elite skiers performed a time to exhaustion (performance) test on a treadmill. Joint kinematics and pole/plantar forces were recorded separately during diagonal roller skiing (9°; 11 km/h). Performance was correlated to cycle length (r = 0.77; P < 0.05), relative leg swing (r = 0.71), and gliding time (r = 0.74), hip flexion range of motion (ROM) during swing (r = 0.73) and knee extension ROM during gliding (r = 0.71). Push-off demonstrated performance correlations for impulse of leg force (r = 0.84), relative duration (r = ? 0.76) and knee flexion (r = 0.73) and extension ROM (r = 0.74). Relative time to peak pole force was associated with performance (r = 0.73). In summary, diagonal roller skiing performance was linked to 1) longer cycle length, 2) greater impulse of force during a shorter push-off with larger flexion/extension ROMs in leg joints, 3) longer leg swing, and 4) later peak pole force, demonstrating the major key characteristics to be emphasised in training.     

Teaching units as the integrating core of mathematics education

How to integrate mathematics, psychology, pedagogy and practical teaching within the didactics of mathematics in order to get unified specific theories and conceptions of mathematics teaching? This problem—relevant for theoretical and empirical studies in mathematics education as well as for teacher training—is considered in the present paper. The author suggests an approach which is based on teaching units (Unterrichtsbeispiele). Suitable teaching units incorporate mathematical, pedagogical, psychological and practical aspects in a natural way and therefore they are a unique tool for integration.     

From Pipelines to Tasting Lemonade: Reconceptualizing College Access

Pipeline metaphors are ubiquitous in theorizing and interpreting college access processes. In this conceptual article, we explore how a lemonade metaphor can open new possibilities to reimagining higher education access and going processes. We argue that using food metaphors, particularly the processes of mixing, tasting, and digesting lemonade, may help constitute new meanings of college going. Rather than focus on production, mechanization, and ignoring social justice, a lemonade metaphor emphasizes the nonlinear aspects of college-going processes, foregrounds power relations within these processes, and humanizes educational purposes and journeys. We encourage educational researchers to take up taste as a heuristic device to reveal something different about educational phenomena that will, in turn, have material consequences.     

Biomechanical aspects of new techniques in alpine skiing and ski-jumping

Abstract

There have been considerable changes in equipment design and movement patterns in the past few years both in alpine skiing and ski-jumping. These developments have been matched by methods of analysing movements in field conditions. They have yielded new insights into the skills of these specific winter sports. Analytical techniques have included electromyography, kinetic and kinematic methods and computer simulations. Our aim here is to review biomechanical research in alpine skiing and ski-jumping. We present in detail the techniques currently used in alpine skiing (carving technique) and ski-jumping (V-technique), primarily using data from the authors’ own research. Finally, we present a summary of the most important results in biomechanical research both in alpine skiing and ski-jumping. This includes an analysis of specific conditions in alpine skiing (type of turn, terrain, snow, speed, etc.) and the effects of equipment, materials and individual-specific abilities on performance, safety and joint loading in ski-jumping.     

Biomechanical comparison of the double-push technique and the conventional skate skiing technique in cross-country sprint skiing

Abstract

The aims of the study were to: (1) adapt the “double-push” technique from inline skating to cross-country skiing; (2) compare this new skiing technique with the conventional skate skiing cross-country technique; and (3) test the hypothesis that the double-push technique improves skiing speed in a short sprint. 13 elite skiers performed maximum-speed sprints over 100 m using the double-push skate skiing technique and using the conventional “V2” skate skiing technique. Pole and plantar forces, knee angle, cycle characteristics, and electromyography of nine lower body muscles were analysed. We found that the double-push technique could be successfully transferred to cross-country skiing, and that this new technique is faster than the conventional skate skiing technique. The double-push technique was 2.9 ± 2.2% faster (P < 0.001), which corresponds to a time advantage of 0.41 ± 0.31 s over 100 m. The double-push technique had a longer cycle length and a lower cycle rate, and it was characterized by higher muscle activity, higher knee extension amplitudes and velocities, and higher peak foot forces, especially in the first phase of the push-off. Also, the foot was more loaded laterally in the double-push technique than in the conventional skate skiing technique.     

“When you’re down,stay down”:A lesson for all competitive alpine skiers supported by an ACL rupture measured in vivo

Background:During an experiment,a ski racer equipped with various measurement devices suffered an anterior cruciate ligament(ACL)rupture in his right knee.The aim of this study was to describe the underlying injury mechanism from a functional perspective.Methods:Eight giant slalom turns(i.e.,4 left turns),followed by 1 left turn at which the ACL injury occurred,were recorded by 2 video cameras,electromyography of 4 relevant muscle groups,inertial measurement units to measure knee and hip angles,and pressure insoles to determine ground reaction forces.Results:Due to a loss of balance,the ski racer began to slide sideways at the apex of a left turn.During sliding,his right(outside)leg was actively abducted upward without touching the ground.The ski racer then attempted to stand up again by dropping his leg back towards the snow surface.The end of this dropping was accompanied by a decrease in electromyographic activity in the knee stabilizing muscles.Once the inside edge of the outer ski caught the snow surface,a rapidly increasing peak force,knee flexion,and an aggressive sudden activation of the vastus medialis muscle were observed,while biceps femoris and rectus femoris further decreased their activation levels.This likely resulted in excessive anterior translation of the tibia relative to the femur,causing damage to the ACL.Conclusion:Our example emphasizes that ski racers should not get up until they stop sliding.Remember:“When you’re down,stay down.”     

‘There’s stuff that comes with being an unexpected guest’: experiences of trans* academics with microaggressions

Historically, minority stress theory focused on the experiences of ‘sexual minorities;’ this study extends minority stress theory to understand the unique stressors that trans* individuals face in academic workplaces. Using interview data from 10 trans* college and university faculty, I fill a noted gap in the literature and examined the unique stressors that these faculty faced within the academy. In this study, microaggressions, a kind of minoritized stress, included: (mis)recognition, including misgendering and mispronouning, being an impossible person, and tokenization. Additionally, trans* faculty reported strategies to resist these stressors. These findings suggest that trans* academics navigate hostile academic work environments and experience minoritized stress deriving from their minoritized gender identities. Implications for research indicate that addressing the personal and professional consequences of minoritized stressors is an important step in understanding how microaggressions affect trans* academics. Implications for practice include the need for rethinking cisnormative assumptions within academe.