Why road trips can make you exhausted just by sitting still

By William Emond | CNN

Departure to and return from summer vacations seem moments especially prone to the stealthy advances of this sickness. We (or at least those of us inclined to travel sickness) are more often ill during these particular journeys than during our normal comings and goings.

Let’s note too that lots of travelers feel a sense of fatigue, drowsiness, apathy or lack of energy without having done any particularly exhausting activity. These are in fact symptoms of mild motion sickness, which show that many more people are affected by the condition than you’d think.

Why this apparent heightened susceptibility during vacation trips? There are many reasons. Compared to normal travel, these journeys feature certain conditions, all with the potential to increase the incidence and severity of symptoms. Here are some pieces of explanation, and advice to minimize the risk.

Long journeys – repetition of movements that make you queasy

In a car, the further one travels, the more likely one is to feel ill, as shown by a number of mathematical models which predict motion sickness.

It’s the adding up of unpleasant movements which takes us over the threshold where we feel symptoms. For certain people, this can happen after just a few minutes; for others it develops more slowly. Only on long journeys, after several hours on the road, in the air or on a boat, will this latter group be pushed over their limit and start feeling unwell.

Activities undertaken to pass the time during a long journey could add to feelings of queasiness. Often people do something to occupy and entertain themselves: read a book, watch a film, play a video game or scroll through social media. Except, these visually stimulating activities absorb our attention to the point that we’re not tuned in to the visual cues that allow our brain to assess the movement of the vehicle. This creates a confusion in the perception of movement. As a result, it becomes much easier to feel sick.

Journey conditions: risks adding up

In summer, the temperature inside a vehicle is difficult to control, with the sun often imposing a stifling heat; conditions which tend to accentuate the symptoms of motion sickness.

When it’s hot, our body has to make an effort to regulate its temperature, through sweat or breathing for example. These various signals amount to “primary symptoms” as they can contribute to the appearance of other more substantive symptoms: dilation of the blood vessels, sickness, nausea or vomiting, as applicable.

To counter these effects, one is tempted to switch the air conditioning on, which could itself, perversely, worsen the situation for passengers highly susceptible to motion sickness. Ventilation and cabin air systems also push people toward their nausea thresholds.

Unpleasant smells are another factor that can accentuate car sickness symptoms: traffic fumes, cigarette smoke, fetid air or even the smell of leather were identified as the second most common cause of car sickness! These are bigger risk factors at the start of the summer travel season, when air pollution peaks regularly and the sun’s rays heat up materials. It’s also known that there is a region of the brain – the area postrema or chemoreceptor trigger zone – which can trigger over-production of saliva and nausea specifically when certain smells are detected – a protective reflex against toxins and other poisonous substances.

Traffic: a physical and mental imposition