Motion sickness

Motion sickness occurs in connection with travel or movement when an incongruity comes about between visually perceived movement and the vestibular system's sense of bodily movement. Most kinds are considered terrestrial motion sickness, such as being carsick, airsick, seasick, or sick from reality simulation. Symptoms include dizziness, fatigue, vertigo, depressed appetite, nonspecific malaise, gastrointestinal discomfort, (most commonly) nausea, and nausea-caused vomiting[1] (see Sopite syndrome). If the cause of the nausea is not resolved, the sufferer will usually vomit, but vomiting may not relieve the feeling of weakness and nausea, which means the person might continue to vomit until the underlying cause of the nausea is resolved.

A kind of motion sickness with similar symptoms but a possibly different etiology is known as space adaptation syndrome or space motion sickness.

"Nausea" in Greek means seasickness (naus means ship).[2][3]

Motion sickness
SynonymsKinetosis, travel sickness, seasickness, airsickness, carsickness, simulation sickness, space motion sickness, space adaptation syndrome
SpecialtyNeurology

Cause

At present a "fully adequate theory of motion sickness is not presently available" but contemporary sensory conflict theory, referring to "a discontinuity between either visual, proprioceptive, and somatosensory input, or semicircular canal and otolith input", is probably the most thoroughly studied.[4] According to this theory, when the brain presents the mind with two incongruous states of motion; the result is often nausea and other symptoms of disorientation known as motion sickness. Such conditions happen when the vestibular system and the visual system do not present a synchronized and unified representation of one's body and surroundings.

According to sensory conflict theory, the cause of terrestrial motion sickness is the opposite of the cause of space motion sickness. The former occurs when one perceives visually that one's surroundings are relatively immobile while the vestibular system reports that one's body is in motion relative to its surroundings.[5] The latter can occur when the visual system perceives that one's surroundings are in motion while the vestibular system reports relative bodily immobility (as in zero gravity.)

A variation of the sensory conflict theory is known as neural mismatch, implying a mismatch occurring between ongoing sensory experience and long-term memory rather than between components of the vestibular and visual systems. This theory emphasizes "the limbic system in the integration of sensory information and long-term memory, in the expression of the symptoms of motion sickness, and the impact of anti-motion-sickness drugs and stress hormones on limbic system function. The limbic system may be the neural mismatch center of the brain."[6]

A very different alternate is the defense mechanism theory holding that motion sickness functions as a defense mechanism against neurotoxins.[7] The area postrema in the brain is responsible for inducing vomiting when poisons are detected, and for resolving conflicts between vision and balance. When feeling motion but not seeing it (for example, in the cabin of a ship with no portholes), the inner ear transmits to the brain that it senses motion, but the eyes tell the brain that everything is still. As a result of the incongruity, the brain concludes that the individual is hallucinating and further concludes that the hallucination is due to poison ingestion. The brain responds by inducing vomiting, to clear the supposed toxin. Treisman's indirect argument has recently been questioned via an alternative direct evolutionary hypothesis, as well as modified and extended via a direct poison hypothesis.[8] The direct evolutionary hypothesis essentially argues that there are plausible means by which ancient real or apparent motion could have contributed directly to the evolution of aversive reactions, without the need for the co-opting of a poison response as posited by Treisman. Nevertheless, the direct poison hypothesis argues that there still are plausible ways in which the body's poison response system may have played a role in shaping the evolution of some of the signature symptoms that characterize motion sickness.

Yet another theory, also as the nystagmus hypothesis,[9] has been proposed based on stimulation of the vagus nerve resulting from the stretching or traction of extra-ocular muscles [1] co-occurring with eye movements caused by vestibular stimulation. There are three critical aspects to the theory: first is the close linkage between activity in the vestibular system, i.e., semicircular canals and otolith organs, and a change in tonus among various of each eye's six extra-ocular muscles. Thus, with the exception of voluntary eye movements, the vestibular and oculomotor systems are thoroughly linked. Second is the operation of Sherrington's Law[10] describing reciprocal inhibition between agonist-antagonist muscle pairs, and by implication the stretching of extraocular muscle that must occur whenever Sherrington's Law is made to fail, thereby causing an unrelaxed (contracted) muscle to be stretched. Finally, there is the critical presence of afferent output to the Vagus nerves as a direct result of eye muscle stretch or traction.[11] Thus, 10th nerve stimulation resulting from eye muscle stretch is proposed as the cause of motion sickness. The theory explains why labyrinthine-defective individuals are immune to motion sickness;[12][13] why symptoms emerge when undergoing various body-head accelerations; why combinations of voluntary and reflexive eye movements may challenge the proper operation of Sherrington's Law, and why many drugs that suppress eye movements also serve to suppress motion sickness symptoms.[14]

A recent theory [15] argues that the main reason motion sickness occurs is due to an imbalance in vestibular outputs favoring the semicircular canals (nauseogenic) vs. otolith organs (anti-nauseogenic). This theory attempts to integrate previous theories of motion sickness. For example, there are many sensory conflicts that are associated with motion sickness and many that are not, but those in which canal stimulation occurs in the absence of normal otolith function (e.g., 0-g) are the most provocative. The vestibular imbalance theory is also tied to the different roles of the otoliths and canals in autonomic arousal (otolith output more sympathetic).

Susceptibility

Roughly one-third of the population is highly susceptible to motion sickness, and most of the rest may get motion sickness under extreme conditions. The incidence of space motion sickness has been estimated over the years at between forty and eighty percent of those who have entered weightless orbit. Several factors influence susceptibility to motion sickness, including sleep deprivation and the cubic footage allocated to each space traveler. Statistics indicate that women are more likely to be affected than men, and that the risk decreases with advancing age. There is some evidence that people with Asian ancestry may suffer motion sickness more frequently compared with people of European ancestry, and there are situational and behavioral factors, such as whether a passenger has a view of the road ahead, and diet and eating behaviors.[16]

Types

Motion sickness can be divided into three categories:

  1. Motion sickness caused by motion that is felt but not seen, as in terrestrial motion sickness;
  2. Motion sickness caused by motion that is seen but not felt, as in space motion sickness;
  3. Motion sickness caused when both systems detect motion but they do not correspond, as in either terrestrial or space motion sickness.

Motion is felt but not seen

In these cases, motion is sensed by the vestibular system and hence the motion is felt, but no motion or little motion is detected by the visual system, as in terrestrial motion sickness.

Carsickness

A specific form of terrestrial motion sickness, being carsick is quite common and evidenced by disorientation while reading a map, a book, or a small screen during travel. Carsickness results from the sensory conflict arising in the brain from differing sensory inputs. Motion sickness is caused by a conflict between signals arriving in the brain from the inner ear, which forms the base of the vestibular system, the sensory apparatus that deals with movement and balance, and which detects motion mechanically. If someone is looking at a stationary object within a vehicle, such as a magazine, their eyes will inform their brain that what they are viewing is not moving. Their inner ears, however, will contradict this by sensing the motion of the vehicle.[17] Varying theories exist as to cause. The sensory conflict theory notes that the eyes view motion while riding in the moving vehicle while other body sensors sense stillness, creating conflict between the eyes and inner ear. Another suggests the eyes mostly see the interior of the car which is motionless while the vestibular system of the inner ear senses motion as the vehicle goes around corners or over hills and even small bumps. Therefore, the effect is worse when looking down but may be lessened by looking outside of the vehicle.

In the early 20th century, Austro-Hungarian scientist Robert Barany observed the back and forth movement of the eyes of railroad passengers as they looked out the side windows at the scenery whipping by. He called it "railway nystagmus." Also called "optokinetic nystagmus." It causes nausea and vomiting. His findings were published in the journal Laeger, 83:1516, Nov.17, 1921.

Airsickness

Air sickness is a kind of terrestrial motion sickness induced by certain sensations of air travel.[5] It is a specific form of motion sickness and is considered a normal response in healthy individuals. It is essentially the same as carsickness but occurs in an airplane. An airplane may bank and tilt sharply, and unless passengers are sitting by a window, they are likely to see only the stationary interior of the plane due to the small window sizes and during flights at night. Another factor is that while in flight, the view out of windows may be blocked by clouds, preventing passengers from seeing the moving ground or passing clouds.

Seasickness

Seasickness is a form of terrestrial motion sickness characterized by a feeling of nausea and, in extreme cases, vertigo experienced after spending time on a watercraft such as a boat or ship.[5] It is essentially the same as carsickness, though the motion of a watercraft tends to be more regular. It is typically brought on by the rocking motion of the craft[18][19] or movement while the craft is immersed in water.[20] As with airsickness, it can be difficult to visually detect motion even if one looks outside the boat since water does not offer fixed points with which to visually judge motion. Poor visibility conditions, such as fog, may worsen seasickness. The greatest contributor to seasickness is the tendency for people being affected by the rolling or surging motions of the craft to seek refuge below decks, where they are unable to relate themselves to the boat's surroundings and consequent motion. Some sufferers of carsickness are resistant to seasickness and vice versa. Adjusting to the craft's motion at sea is called "gaining one's sea legs"; it can take a significant portion of the time spent at sea after disembarking to regain a sense of stability "post-sea legs".

Centrifuge motion sickness

Rotating devices such as centrifuges used in astronaut training and amusement park rides such as the Rotor, Mission: Space and the Gravitron can cause motion sickness in many people. While the interior of the centrifuge does not appear to move, one will experience a sense of motion. In addition, centrifugal force can cause the vestibular system to give one the sense that downward is in the direction away from the center of the centrifuge rather than the true downward direction.

Dizziness due to spinning

When one spins and stops suddenly, fluid in the inner ear continues to rotate causing a sense of continued spinning while one's visual system no longer detects motion.

Virtual reality disorientation

Usually, VR programs would detect the motion of the user's head and abject the rotation of vision to avoid dizziness. However, some cases such as system lagging or software crashing could cause lags in the screen updates. In such cases, even some small head motions could trigger the motion sickness.

Motion seen but not felt

In these cases, motion is detected by the visual system and hence the motion is seen, but no motion or little motion is sensed by the vestibular system. Motion sickness arising from such situations has been referred to as "visually induced motion sickness" (VIMS).[21]

Space motion sickness

Zero gravity interferes with the vestibular system's gravity-dependent operations, so that the two systems, vestibular and visual, no longer provide a unified and coherent sensory representation. This causes unpleasant disorientation sensations often quite distinct from terrestrial motion sickness, but with similar symptoms. The symptoms may be more intense because a condition caused by prolonged weightlessness is usually quite unfamiliar.

Space motion sickness was effectively unknown during the earliest spaceflights because the very cramped conditions of the spacecraft allowed for only minimal bodily motion, especially head motion. Space motion sickness seems to be aggravated by being able to freely move around, and so is more common in larger spacecraft.[5] Around 60% of Space Shuttle astronauts currently experience it on their first flight; the first case of space motion sickness is now thought to be the Soviet cosmonaut Gherman Titov, in August 1961 onboard Vostok 2, who reported dizziness, nausea, and vomiting. The first severe cases were in early Apollo flights; Frank Borman on Apollo 8 and Rusty Schweickart on Apollo 9. Both experienced identifiable and quite unpleasant symptoms-—in the latter case causing the mission plan to be modified.

Disorientation from films, video games, and other screen images

This type of terrestrial motion sickness is particularly prevalent when susceptible people are watching films presented on very large screens such as IMAX, but may also occur in regular format theaters or even when watching TV or playing games. For the sake of novelty, IMAX and other panoramic type theaters often show dramatic motions such as flying over a landscape or riding a roller coaster. This type of motion sickness can be prevented by closing one's eyes during such scenes.

In regular-format theaters, an example of a movie that caused motion sickness in many people is The Blair Witch Project. Theaters warned patrons of its possible nauseating effects, cautioning pregnant women in particular. Blair Witch was filmed with a handheld camcorder, which was subjected to considerably more motion than the average movie camera,[22] and lacks the stabilization mechanisms of steadicams.

Home movies, often filmed with a cell phone camera, also tend to cause motion sickness in those who view them. The person holding the cell phone or other camera usually is unaware of this as the recording is being made since the sense of motion seems to match the motion seen through the camera's viewfinder. Those who view the film afterward only see the movement, which may be considerable, without any sense of motion. Using the zoom function seems to contribute to motion sickness as well since zooming is not a normal function of the eye. The use of a tripod or a camera or cell phone with image stabilization while filming can reduce this effect.

Virtual reality disorientation

Helmet Vision - VR helmet
The company HELMET VISION Introduced a panoramic lens in the device, which reduces the effect of seasickness.

Terrestrial motion sickness due to virtual reality is very similar to simulation sickness and motion sickness[23] due to films. In virtual reality the effect is made more acute as all external reference points are blocked from vision, the simulated images are three-dimensional and in some cases stereo sound that may also give a sense of motion. The NADS-1, a simulator located at the National Advanced Driving Simulator, is capable of accurately stimulating the vestibular system with a 360-degree horizontal field of view and 13 degrees of freedom motion base.[24] Studies have shown that exposure to rotational motions in a virtual environment can cause significant increases in nausea and other symptoms of motion sickness.[25]

In a study conducted by the U.S. Army Research Institute for the Behavioral and Social Sciences in a report published May 1995 titled "Technical Report 1027 - Simulator Sickness in Virtual Environments", out of 742 pilot exposures from 11 military flight simulators, "approximately half of the pilots (334) reported post-effects of some kind: 250 (34%) reported that symptoms dissipated in less than one hour, 44 (6%) reported that symptoms lasted longer than four hours, and 28 (4%) reported that symptoms lasted longer than six hours. There were also four (1%) reported cases of spontaneously occurring flashbacks."[26]

Motion that is seen and felt but whose visual and bodily perception is incongruous

When moving within a rotating reference frame such as in a centrifuge or environment where gravity is simulated with centrifugal force, the coriolis effect causes a sense of motion in the vestibular system that does not match the motion that is seen.

Treatment

Many cures and preventatives for motion sickness have been proposed.

Devices

A motion blocking eyewear device was patented (US patent 6,275,998)[27] to prevent carsickness-related terrestrial motion sickness. Visual cues are an important contributor to land-based vehicular travel in addition to vestibular (inner ear) input. The eyewear device limits what the wearer sees outside the moving vehicle by use of an opaque shield. By removing visual cues outside the vehicle, the device normalizes the visual input dimension involved in sensory conflict, a leading theory behind motion sickness. No evidence exists that motion blocking eyewear alters or eliminates vestibular input or that of other bodily receptors. Carsickness is the most common type of motion sickness given the number of travelers traveling over land versus those traveling by air or sea.

A head-worn, computer device with a transparent display can be used to mitigate the effects of motion sickness (and spatial disorientation) if visual indicators of the wearer’s head position are shown.[28] Such a device functions by providing the wearer with digital reference lines in their field of vision that indicate the horizon’s position relative to the user’s head. This is accomplished by combining readings from accelerometers and gyroscopes mounted in the device (US Patent 5,966,680).[29] This technology has been implemented in both standalone devices[30] and Google Glass.[31][32] In two NIH-backed studies, greater than 90% of patients experienced a reduction in the symptoms of motion sickness while using this technology.[28]

Activity

One common suggestion is to simply look out the window of the moving vehicle and to gaze towards the horizon in the direction of travel. This helps to re-orient the inner sense of balance by providing a visual reaffirmation of motion.

In the night, or in a ship without windows, it is helpful to simply close one's eyes, or if possible, take a nap. This resolves the sensory conflict between the eyes and the inner ear. Napping also helps prevent psychogenic effects (i.e. the effect of sickness being magnified by thinking about it).

Fresh, cool air can also relieve motion sickness slightly, although it is likely this is related to avoiding foul odors which can worsen nausea.[33]

While playing computer games, and mainly in first-person shooter games, some cases of simulation sickness can be resolved by changing the field of view in the game. Some games have a default setting which places a player's vision a small distance ahead of the actual object controlled, which will most likely trigger simulation sickness.

Medication

Over-the-counter and prescription medications are readily available, such as dimenhydrinate,[34] scopolamine,[35] meclizine, promethazine, cyclizine, and cinnarizine.[36] Cinnarizine is not available in the United States, as it is not approved by the FDA. As these medications often have side effects, anyone involved in high-risk activities while at sea (such as SCUBA divers) must evaluate the risks versus the benefits.[37][38][39][40][41] Promethazine is especially known to cause drowsiness, which is often counteracted by ephedrine in a combination known as "the Coast Guard cocktail.".[42] There are special considerations to be aware of when the common anti-motion sickness medications are used in the military setting where performance must be maintained at a high level.[38]

Scopolamine is effective[35] and is sometimes used in the form of transdermal patches (1.5 mg) or as a newer tablet form (0.4 mg). The selection of a transdermal patch or scopolamine tablet is determined by a doctor after consideration of the patient's age, weight, and length of treatment time required.

Many pharmacological treatments which are effective for nausea and vomiting in some medical conditions may not be effective for motion sickness. For example, metoclopramide and prochlorperazine, although widely used for nausea, are ineffective for motion-sickness prevention and treatment. This is due to the physiology of the CNS vomiting centre and its inputs from the chemoreceptor trigger zone versus the inner ear. Sedating anti-histamine medications such as promethazine work quite well for motion sickness, although they can cause significant drowsiness.[43]

Ginger root is commonly thought to be an effective anti-emetic, but it is ineffective in treating motion sickness.[44]

Electronic

As astronauts frequently have motion sickness, NASA has done extensive research on the causes of and treatments for motion sickness. One very promising looking treatment is for the person suffering from motion sickness to wear LCD shutter glasses that create a stroboscopic vision of 4 Hz with a dwell of 10 milliseconds.[45]

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External links

External resources
Acupressure

Acupressure [from Latin acus "needle" (see acuity) + pressure (n.)] is an alternative medicine technique similar in principle to acupuncture. It is based on the concept of life energy which flows through "meridians" in the body. In treatment, physical pressure is applied to acupuncture points with the aim of clearing blockages in these meridians. Pressure may be applied by hand, by elbow, or with various devices.

Some medical studies have suggested that acupressure may be effective at helping manage nausea and vomiting, for helping lower back pain, tension headaches, stomach ache, among other things, although such studies have been found to have a high likelihood of bias. Like many alternative medicines, it may benefit from a placebo effect.

According to Quackwatch, acupressure is a dubious practice and its practitioners use irrational methods.

Airsickness

Airsickness is a sensation which is induced by air travel. It is a specific form of motion sickness, and is considered a normal response in healthy individuals. Airsickness occurs when the central nervous system receives conflicting messages from the body (including the inner ear, eyes and muscles) affecting balance and equilibrium.

Whereas commercial airline passengers may simply feel poorly, the effect of airsickness on military aircrew may lead to a decrement in performance and adversely affect the mission.The inner ear is particularly important in the maintenance of balance and equilibrium because it contains sensors for both angular (rotational) and linear motion. Airsickness is usually a combination of spatial disorientation, nausea and vomiting.

Antiemetic

An antiemetic is a drug that is effective against vomiting and nausea. Antiemetics are typically used to treat motion sickness and the side effects of opioid analgesics, general anaesthetics, and chemotherapy directed against cancer. They may be used for severe cases of gastroenteritis, especially if the patient is dehydrated.

Antiemetics, though previously thought to cause birth defects, have been proven safe for use by pregnant women in the treatment of morning sickness and the more serious hyperemesis gravidarum.

Benzylamine

Benzylamine is an organic chemical compound with the condensed structural formula C6H5CH2NH2 (sometimes abbreviated as PhCH2NH2 or BnNH2). It consists of a benzyl group, C6H5CH2, attached to an amine functional group, NH2. This colorless liquid is a common precursor in organic synthesis and used in the industrial production of many pharmaceuticals. The hydrochloride salt was used to treat motion sickness on the Mercury-Atlas 6 mission in which NASA astronaut John Glenn became the first American to orbit the Earth.

Bárány chair

The Barany chair or Bárány chair, named for the Hungarian physiologist Robert Bárány, is a device used for aerospace physiology training, particularly for student pilots.

Cinnarizine

Cinnarizine is an antihistamine and calcium channel blocker of the diphenylmethylpiperazine group. It is also known to promote cerebral blood flow, and so is used to treat cerebral apoplexy, post-trauma cerebral symptoms, and cerebral arteriosclerosis. However, it is more commonly prescribed for nausea and vomiting due to motion sickness or other sources such as chemotherapy, vertigo, or Ménière's disease.Cinnarizine was first synthesized as R1575 by Janssen Pharmaceutica in 1955. The nonproprietary name is derived from the cinnamyl substituent on one of the nitrogen atoms, combined with the generic ending "-rizine" for "antihistaminics/cerebral (or peripheral) vasodilators". It is not available in the United States or Canada. It has also been cited as one of the most used drugs for seasickness within the British Royal Navy.

Dimenhydrinate

Dimenhydrinate, marketed as Dramamine and Gravol among others, is an over-the-counter medication used to treat motion sickness and nausea. Dimenhydrinate is a combination, or a salt of two drugs: diphenhydramine and 8-chlorotheophylline.

It is most commonly prepared as tablets, although it is also available in liquid form and as a suppository.

Hyoscine

Hyoscine, also known as scopolamine, is a medication used to treat motion sickness and postoperative nausea and vomiting. It is also sometimes used before surgery to decrease saliva. When used by injection, effects begin after about 20 minutes and last for up to 8 hours. It may also be used by mouth and as a skin patch.Common side effects include sleepiness, blurred vision, dilated pupils, and dry mouth. It is not recommended in people with glaucoma or bowel obstruction. It is unclear if use during pregnancy is safe; however, it appears to be safe during breastfeeding. Hyoscine is in the antimuscarinic family of medications and works by blocking some of the effects of acetylcholine within the nervous system.Hyoscine was first written about in 1881 and started to be used for anesthesia around 1900. It is on the WHO Model List of Essential Medicines, the most effective and safe medicines needed in a health system. Hyoscine is produced from plants of the nightshade family. The name "scopolamine" is derived from one type of nightshade known as Scopolia while the name "hyoscine" is derived from another type known as Hyoscyamus niger.

Meclizine

Meclizine (INN, or meclozine) is an antihistamine of the diphenylmethylpiperazine group considered to be an antiemetic. It is sold under the brand names Bonine, Bonamine, Antivert, Postafen, Sea Legs, and Dramamine II (Less Drowsy Formulation). Emesafene is a combination of meclizine (1/3) and pyridoxine (2/3). In Canada, Antivert Tab (which is no longer available) was a combination of meclizine and nicotinic acid.

Micro-g environment

The term micro-g environment (also µg, often referred to by the term microgravity) is more or less a synonym for weightlessness and zero-g, but indicates that g-forces are not quite zero—just very small. The symbol for microgravity, µg, was used on the insignias of Space Shuttle flights STS-87 and STS-107, because these flights were devoted to microgravity research in low Earth orbit.

Motion Sickness (song)

"Motion Sickness" is a song by the band Bright Eyes. It was released as a single by Blood of the Young records. It was originally limited to 1100 copies on black vinyl, but has since been repressed on transparent yellow (2200 copies) and multi-colored swirl (3300 copies).

Cover photographs and layout by Casey Scott.

Nausea

Nausea is an unpleasant, diffuse sensation of unease and discomfort, often perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged, and has been described as placing discomfort on the chest, upper abdomen, or back of the throat.Like pain, the purpose of nausea is to discourage the person or animal from repeating whatever caused the unpleasantness. The memory of pain elicits safer or evasive actions; the memory of nausea elicits revulsion towards whatever was eaten before vomiting it up — even if it was not the cause of the nausea.Nausea is a non-specific symptom, which means that it has many possible causes. Some common causes of nausea are motion sickness, dizziness, migraine, fainting, low blood sugar, gastroenteritis (stomach infection) or food poisoning. Nausea is a side effect of many medications including chemotherapy, or morning sickness in early pregnancy. Nausea may also be caused by anxiety, disgust and depression.Medications taken to prevent and treat nausea are called antiemetics. The most commonly prescribed antiemetics in the US are promethazine, metoclopramide and the newer, extremely effective ondansetron. The word nausea is from Latin nausea, from Greek ναυσία – nausia, "ναυτία" – nautia, motion sickness, "feeling sick or queasy".

Sickness bag

A sickness bag (also known as a sick sack, airsick bag, airsickness bag, emesis bag, sick bag, barf bag, vomit bag, disposal bag, waste bag or motion sickness bag) is a small bag commonly provided to passengers on board airplanes and boats to collect and contain vomit in the event of motion sickness. Hovercraft-ferry operators and even train companies have also been known to furnish bags. Pregnant women with morning sickness and travelers who know they are prone to motion sickness will sometimes bring their own bags.

The plastic-lined airsickness bag was created by inventor Gilmore Schjeldahl for Northwest Orient Airlines in 1949. Previously bags had been made from waxed paper or card. Modern bags are still mainly made from plastic-lined paper, but a significant proportion are now made completely from plastic.

Simulator sickness

Simulator sickness is a subset of motion sickness that is typically experienced by pilots who undergo training for extended periods of time in flight simulators. Due to the spatial limitations imposed on these simulators, perceived discrepancies between the motion of the simulator and that of the vehicle can occur and lead to simulator sickness.

It is similar to motion sickness in many ways, but occurs in simulated environments and can be induced without actual motion. Symptoms of simulator sickness include discomfort, apathy, drowsiness, disorientation, fatigue, vomiting, and many more.

These symptoms can reduce the effectiveness of simulators in flight training and result in systematic consequences such as decreased simulator use, compromised training, ground safety, and flight safety. Pilots are less likely to want to repeat the experience in a simulator if they have suffered from simulator sickness and hence can reduce the number of potential users. It can also compromise training in two safety-critical ways:

It can distract the pilot during training sessions.

It can cause the pilot to adopt certain counterproductive behaviors to prevent symptoms from occurring.Simulator sickness can also have post-training effects that can compromise safety after the simulator session, such as when the pilots drive away from the facility or fly while experiencing symptoms of simulator sickness.

Ski sickness

Ski sickness or Häusler's disease is a form of motion sickness which is suffered by some skiers when weather conditions are bad. Poor visibility in heavy fog can bring on the condition as well as psychological factors such as fear of heights or fear of mountains. High speed and falling may also contribute as when descending rapidly atmospheric pressure changes in the ear from high to low altitude. Symptoms are similar to other sicknesses brought about by motion and include: dizziness, headaches and nausea and in more extreme cases vomiting.In whiteout conditions, the brain is unable to determine orientation or movement accurately. The condition is caused by the rhythmic turning motion of skiing and other effects such as a reduction in sensory feedback from constrained feet.

In 1995 Rudolf Häusler of the University of Berne was the first described to suffer from this disease. Ski sickness could affect up to 10% of skiers.

Professor Häusler found that over-the-counter prescription medicines for motion sickness relieved the symptoms for most sufferers.

Space adaptation syndrome

Space adaptation syndrome (SAS) or space sickness is a condition experienced by as many as half of all space travelers during their adaptation to weightlessness once in orbit . It is the opposite of terrestrial motion sickness since it occurs when the environment and the person appear visually to be in motion relative to one another even though there is no corresponding sensation of bodily movement originating from the vestibular system.

Tricyclic

Tricyclics are chemical compounds that contain three interconnected rings of atoms.

Many compounds have a tricyclic structure, but in pharmacology, the term has traditionally been reserved to describe heterocyclic drugs. Among these are antidepressants, antipsychotics, anticonvulsants, and antihistamines (as antiallergens, anti-motion sickness drugs, antipruritics, and hypnotics/sedatives) of the dibenzazepine, dibenzocycloheptene, dibenzothiazepine, dibenzothiepin, phenothiazine, and thioxanthene chemical classes, and others.

Virtual reality sickness

Virtual reality sickness occurs when exposure to a virtual environment causes symptoms that are similar to motion sickness symptoms. The most common symptoms are general discomfort, headache, stomach awareness, nausea, vomiting, pallor, sweating, fatigue, drowsiness, disorientation, and apathy. Other symptoms include postural instability and retching. Virtual reality sickness is different from motion sickness in that it can be caused by the visually-induced perception of self-motion; real self-motion is not needed. It is also different from simulator sickness; non-virtual reality simulator sickness tends to be characterized by oculomotor disturbances, whereas virtual reality sickness tends to be characterized by disorientation.

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