Nathan Scott

Measurement of ski snow-pressure profiles

Bulge-disc type pressure sensors of diameter 6 mm were fitted as near as possible to the running edge of a modern carved ski. The pressure signals were sampled at 30 Hz during long turns on snow, synchronously with signals from a geomagnetic compass and a pressure pad in the ski boot. The pressure from the snow was found to be highly variable with a mean value of about 50 kPa and dynamic pressure spikes up to 300 kPa. With the outside leg, the snow contact width in the rear part of the ski was found to be slightly wider, on average, than for the front part, as expected for a carving turn. Correlation within the pressure sensor data showed that the rapid pressure fluctuations were probably not due to bumps or features on the snow; instead they were probably caused by many small-scale collapses of the snow structure as the ski passed.

Addressing current problems in teaching pathology to medical students: blended learning

Background: Forces influencing the remodelling of medical curricula have clouded the visibility of pathology teaching yet its mastery is central to the study of medicine. The shortage in the workforce available for routine clinical diagnosis, research and teaching, and increasing student numbers have driven the development of innovative teaching methods. Aims: To develop teaching methods which improved student satisfaction and engagement in their learning of pathology, and which also accommodated larger classes. Methods: An iterative development cycle adopting effective use of the web and sound instructional design pedagogies was followed. Two face-to-face formats, i.e. small group and large group, and a self-directed web-based (online) format were implemented on a cohort of 220 third year medical students. Outcomes were evaluated by analysis of a student preceptions questionnaire and of students’ web footprints in the online resource. Results: Themes relating to teaching techniques, learning preferences and accessibility issues emerged as significant in the students’ perceptions. Measures of user “online avidity”, “case breadth compliance” and “formative assessment compliance/diligence” were determined by comparing historical behaviour in the web resource with patterns of use within these modules. Students who were proven avid online users entered the resource more frequently than less avid users. However less avid online users did not necessarily access a narrower breadth of cases than avid online users. Students who made maximal use of the web formative assessments tended to have better summative outcomes. Conclusions: The students adopted the online resource as a learning tool. The optimal combination of small group face-to-face tutorials and the self-directed web-based (online) format improved pathology teaching, partly because it satisfied a broader range of learning styles in students. The cycle used of develop, implement, evaluate was successful as it engaged the students, was evidence based and driven by discipline experts who were commited teachers.

Timing of Force Application and Joint Angles During a Long Ski Turn

Using a measuring system which is described in detail in another paper in this conference, the load on the ski, sole pressure, leg joint motion, and turn direction have been measured during a long turn of an expert skier. The instant of turn change was associated with a change in the sign of the force moment about the ski direction. The total force on the outside ski was generally about double that on the inside ski, while both loads instantly decreased at the turn change. Foot pressure increased at the heel area during the steering process. The center of the pressure was always kept in the rear part near the heel, but it moved forward at the turn change. The main motion of the leg was a combination of flexion-extension of the hip joint, knee joint and ankle joint. The outside leg was kept extended angle during the steering process, while the inside leg gradually flexed and extended. The trajectory of the body was estimated from the data of a magnetic compass at the backpack. The forces, foot pressure, joint motion and body trajectory were compared with the video image of the skier. This comparison showed that the skier made the turn change earlier than the centerline of the turn trajectory. During the turn change process, the skier first extended the previous inside leg without flexing the outside leg. Next, he shifted the main load from the previous outside leg to the other leg; at this time the force moment also changed. Then he flexed the new inside leg. We think that the timing of these motions is the main factor determining the downhill speed achieved.

A Unified, Custom-built Measuring System for a Ski Athlete

At the previous ISEA conference (in Davis 2004) we reported on our work measuring a ski athlete. Each summer we add new functions to the measuring system and each winter we test the functions on the snow field. This paper is a description of the system as it was in March 2005, and is meant to provoke discussion of measurement and design issues.