A sleeping posture favoured by many people may be interfering with a good night's rest, according to a survey that suggests nearly four in 10 Canadians have woken up in pain.

The "arrow" position, or sleeping on your side with the legs straight, was the most popular sleeping posture at 39 per cent, but experts said it may place stress on the spine and pelvis.

People often assume many positions at night, but the arrow is a common starting point, said Kathy Kawaja, a certified ergonomist in Ontario speaking on behalf of the mattress industry's Better Sleep Council.

Sleeping on the side is a plus for the arrow, but the legs are straight and one hand is tucked up underneath the pillow, which is ergonomically undesirable.

The downside of the arrow is that the hips and pelvis are not in a neutral position, which can put some strain on both, as well as the lower back, adding to discomfort, Kawaja said.

Regularly sleeping in poor postures may deform the structure of the backbone and lead to chronic joint and muscle strain, as well as headaches and poor posture.

The tuck or fetal position is preferred for the back, but a pillow between the knees is recommended to help maintain a neutral alignment of the spine.

"The head pillow should actually be angled so that the area between the ear and the mattress is supported," Kawaja told CBC Newsworld on Tuesday.

Or are you a zombie?

According to the poll of 1,000 Canadian adults, the "zombie" position on the back with arms straight down by the side was favoured by 15 per cent.

With the zombie, there is overextension in the lower back area, which could add strain by the end of the night, Kawaja said. Again, body pillows are recommended underneath the knees.

Exaggerated fetal positions or sleeping on the stomach should be avoided, although face down in the pillow was favoured by 17 per cent of students, compared with eight per cent nationally in the survey.

About 44 per cent of Canadians who sleep with a partner reported sleeping in separate positions, compared with 28 per cent who said they both sleep on their side.

The poll was conducted by Decima from April 5-9, and is considered accurate within plus or minus 3.1 percentage points, 19 times out of 20.