What is motion sickness

Defining Motion, Sea and Air Sickness

Almost everybody can suffer from motion sickness at some point in their lives. Why some people suffer more than others is unclear. It is known that a predisposition to it is hereditary and that a person with a first-rate vestibular system, which is responsible for walking, balance and spatial awareness, is also more likely to suffer.

Motion sickness is a condition characterised by feeling unwell and nauseous when bodily motion or perceived motion is experienced. This feeling can extend to many symptoms, including:

  • Stomach awareness
  • Sweating
  • Nausea and dizziness
  • Increased salivation
  • Sensations of bodily warmth
  • Drowsiness
  • Loss of appetite
  • Increased sensitivity to odours
  • Headache and migraine

The symptom of facial pallor can result in the sufferer’s face ‘turning green’ and when the nausea extends to vomiting often little relief is experienced.

Opinion varies as to why motion sickness occurs. The most popular explanation for motion sickness is that it arises from a mismatch of signals received by a part of the brain (the area postrema) from the body’s various sense systems, governing our spatial awareness.

In simple terms, sickness is experienced when the brain receives conflicting messages from the body’s balance receptors: the inner ears (vestibular system), the eyes (visual system), and the muscles down the back all the way to the feet (proprioceptive system). When you’re in any moving vehicle , your inner ear and muscles signal that you’re moving, but your eyes say that you’re not – because your body is motionless in relation to its immediate environment, such as your seat, the floor, or the seat in front. Your brain becomes confused and you feel sick.

According to one popular theory by Dr M Treisman in 1977, motion sickness is the result of a primeval defence system, evolved way before travelling on vehicles had been thought of. This theory suggests that your brain deduces incorrectly that you have eaten poisonous berries, fungi or animal food which have caused you to hallucinate (seeing movement when you are not actually moving). In an attempt to expel the poison, it instructs your stomach to empty its contents by vomiting. A fascinating and complex system indeed and understandably it seems likely that the human evolutionary process is not keeping up with man’s desire to travel other than on foot!

Another theory which has gained credibility is the link between optokinetic nystagmus (OKN) and motion sickness. OKN is a gaze stabilising mechanism in which eye movements attempt to identify things that are moving. It is readily seen when a passenger on a fast moving train for example, is trying to fix on the name of a station while the train is passing through it. An alternating sequence of slow eye movements in the direction of the station name sign whizzing past and fast jerking eye movements in the other direction occur. It is the resultant irregular signals to the brain that are thought to bring on sickness.

Travellers and sea-farers have documented their struggle with motion sickness since the earliest times. Hippocrates, the ancient Greek physician, wrote about the condition, while accounts of Julius Caesar’s military campaigns tell of vomiting recruits and sea-sick horses! Any animal with a functioning labyrinthine system (housing for the inner ear) can suffer motion sickness; that’s us and most other mammals!

During the voyages of discovery in the Middle Ages, sea sickness was a constant problem. Even Columbus and his men were affected! Sea-sickness also played a part in England’s ‘against the odds’ victory over the Spanish Armada in 1588. The admiral in command of the Armada was the Duke of Medina Sidonia, a military general who had spent very little time at sea. He suffered severe sea-sickness, and this, on top of other strokes of bad luck, proved disastrous for the Spanish.

Charles Darwin was another person who was chronically seasick, and Lawrence of Arabia is said to have become sick while riding a camel (‘ship of the desert’) through the deserts of Mesopotamia!

Since the invention of TravelShades it would be easy to speculate that pirates of old may have discovered that wearing an eye patch may relieve sea-sickness. Just as likely, however, is that an eye patch may have been used to condition the pirate’s eye so that he may fight better in the dark. It is true that even though a bright light may shine in one eye, the other will retain its dark adaptation if it is protected from the light. A simple trick to see better in the dark is to close one eye or both for a short while. This will allow the pupil of the eye to dilate and let in more light once the eye is opened, so you see more clearly. However, since an eye patch restricts the judgement of distance, the pirate would probably end up tripping overboard anyway. It is safe to say that due to the restricted vision, an eye patch would only be worn if absolutely necessary, perhaps to cover an injured eye. Either way it would be an odd choice of occupation for someone who suffers sea sickness!

Unfortunately, in rare cases, some sea-sickness sufferers continue to experience motion sickness when they are back on land. This is called “mal de debarquement” syndrome (MDD), or “illness after disembarking”. TravelShades have proven helpful in alleviating this nauseous feeling of spinning and swaying which, can last from days to years.

Travel sickness is not just limited to actual travelling experiences. Virtual travelling or motion can also cause sickness and nausea, sometimes referred to as cybersickness. This may happen when playing video games, using simulators or watching films and TV when motion can be seen but not felt by your body. The result is a mismatch of signals to the brain and this confusion leads to nausea and dizziness. This type of motion sickness is generally called visually induced motion sickness (VIMS). Research at the University of Minnesota had students play the video game Halo for less than an hour, and found that up to 50% felt sick afterwards.