Motion of a ship at sea creates challenges for the body. So sea travellers are often told to look at the horizon to overcome the feelings of instability, but is there any truth in that advice?
Now, researchers at the University of Minnesota measured how much people sway on land and at sea and found that fixing their eyes on the horizon could stabilise wobbly posture of those aboard a ship.
Thomas A Stoffregen has been studying ‘body sway’ for decades and wanted to know what it has to do with motion sickness.
In a normal situation, people standing still move back and forth by about four centimetres every 12 to 15 seconds.
Stoffregen and his co-authors wanted to know how this was affected when standing on a ship.
To study posture at sea, Stoffregen contacted the US consortium that runs scientific research ships. He then boarded a ship when it was travelling between different projects.
In this study, he rode on the research vessel Atlantis as it went between two points in the Gulf of California.
The study compared the same people standing on dry land—a dock in Guaymas, Mexico—and aboard the ship.
In each experiment, the crew member stood comfortably on a force plate and focused on a target—either something about 16 inches in front of them, or a far-off point; a distant mountain when standing on land or the horizon when standing on the ship.
The researchers found that people on land were steadier when they looked at the close-up target and swayed more when they looked far away. On the ship, however, they were steadier when they looked at the horizon.
“This is actually counterintuitive. When you’re standing on a ship, you need to adjust to the ship’s movement, or you’ll fall over,” said Stoffregen
He thinks it may help stabilize your body by helping you differentiate between sources of movement—the natural movement coming from your body and the movement caused by the ship.
The study is published in Psychological Science.