We all know it’s uncomfortable — insufferably so. But Canadian aviation expert Jan Davies warns shrinking leg room, or seat pitch, also has serious implications for passengers’ safety in emergencies.

Prof Davies, the chair of the International Board of Research into Aircraft Crash Events, has told an aviation safety conference in Canberra cramped seats were making it difficult for passengers to adopt the brace position in a crash or emergency landing, according to the ABC.

“The seat pitch is the distance essentially between the back of the seat in front of you and your seat back, and airlines have been reducing that distance over the last decade or so,” she said.

“If your seat pitch is less than 30 inches [76.2cm], you will not be able to brace properly if you are of average height … as well as if you are a tall person or a larger person, because there’s just not much space.”

Passengers are instructed to adopt the brace position to prepare for a crash or an emergency landing on land or water.

It usually requires passengers to keep their feet firmly on the floor with knees together, while holding their head against the surface it is most likely to strike on impact, such as the seat in front.

Prof Davies said a person of average height would find they needed to tilt their head, or arch their backs, to adopt the necessary brace position in a seat with a 29 inch (73.7cm) pitch.

Passengers have had to put up with disappearing leg room and seat pitch, as well as shrinking seats, over the past decade as airlines seek to boost income by cramming more seats onto aircraft.

In May, American Airlines said it was slashing the seat pitch on its new Boeing 737 Max jetliners by five centimetres — from 79cm down to 76cm — to allow for extra seats.

But there’s been a strong backlash against the phenomenon, especially in the United States. A passenger rights group in the US has challenged the Federal Aviation Administration’s refusal to set rules on seat sizes and seat pitches in an ongoing legal case that’s been dubbed “the case of the incredible shrinking airline seat”.

Last month, the Daily Beast examined documents from the US Department of Transportation and the Federal Aviation Administration and found newer economy class seating may not provide adequate room for passenger to evacuate their seats in an emergency, creating “a plausible life or death concern” for air travellers.

Skyscanner recently ran a comparison of the seat pitch in economy class on airlines flying in and out of Australia.

It found Jetstar’s economy seats had a pitch of 29 to 30 inches (73.7 to 76.2cm), Qantas had 31 inches (78.7cm), and Virgin Australia and Tigerair both had pitches of 29 to 31 inches (73.7 to 78.7cm).

On Emirates, the economy seat pitch was between 32 and 34 inches (81.3 and 86.4cm), while both Delta Air Lines and Air New Zealand’s economy seats ranged from 31 inches to a very generous 35 inches (73.7 to 88.9cm).