Pulse code modulation telemetry in ski injury research. II. Preliminary results.

The excitation between the boot and the ski was measured in maneuvers skied over a variety of snow conditions. A precision pulse-code modulation (PCM) - frequency modulation (FM) telemetry system was custom built to transmit data from strain-gage force transducers mounted inside the test ski to a receiving station about 3 km distant. Field tests gathered cruising data from three basic maneuvers - snowplow, stem christiana, and parallel christiana. Some classic falls resulting from inadvertent release of the ski bindings were also recorded. For comparative purposes, the maneuvers were skied over a standard five-turn slalom course. Examination of the loading histories reveals that: (1) the data are nonstationary random; (2) boot compression for the test binding system exceeds 500 N and is caused by ski flexure; (3) an 80 Hz resonance of the particular toe binding mechanism is excited; (4) combined impulsive loading is significant; (5) the loading is related to the maneuver type; (6) bending components during forward falls exceed the tibia flexural strength even though heel binding release occurs at the laboratory setting, and (7) torsion and bending components exceed tibia fracture levels during elementary ski maneuvers.