[Sensory illusions in hang-gliding]. / Illusion sensorielles en vol libre.

Sensory illusions in hang-gliding and para-gliding. Hang-gliding and para-gliding are at the moment booming sports. Sensory illusions are physiological phenomena sharing the wrong perception of the pilote's real position in space. These phenomena are very familiar to aeroplane pilotes, they can also be noticed on certain conditions with hang-gliding pilotes. There are many and various sensory illusions, but only illusions of vestibular origin will be dealt with in this article. Vestibular physiology is reminded with the working principle of a semicircular canal. Physiology and laws of physics explain several sensory illusions, especially when the pilote loses his visual landmarks: flying through a cloud, coriolis effect. Also some specific stages of hang-gliding foster those phenomena: spiraling downwards, self-rotation, following an asymetric closing of the parachute, spin on oneself. Therefore a previous briefing for the pilotes seems necessary.

[Motion sickness]. / Les cinétoses.

Motion sickness is a general term covering sea-sickness, car-sickness, air-sickness, and space-sickness. Symptoms can occur when a person is exposed to unfamiliar movement whether real or simulated. Despite progress in the technology and comfort of modern transportation (planes, boats, and overland vehicles), a great number of travelers still experience motion sickness. Bouts are characterized by an initial phase of mild discomfort followed by neurologic and gastro-intestinal manifestations. The delay in onset depends on specific circumstances and individual susceptibility. Attacks are precipitated by conflicting sensory, visual, and vestibular signals but the underlying mechanism is unclear. Most medications used for prevention and treatment (e.g. anticholinergics and antihistamines) induce unwanted sedation. Furthermore no one drug is completely effective or preventive under all conditions.