The weird ways our bodies behave... and why

From hiccups to sleep jerks, bodies often do odd, embarrassing things that seem out of our control. But why, and can we stop them? Tanith Carey finds out...

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Around seven in ten people experience hypnic jerks: sudden, involuntary muscle twitches just as they're falling asleep.

Body jerks as you fall asleep

What are they?

Around seven in ten people experience hypnic jerks: sudden, involuntary muscle twitches just as they're falling asleep.

What causes them?

Usually, the brain sends signals to stop muscles from twitching during sleep.

But as you relax, this blocking mechanism may pause, allowing the muscles to jolt. Another theory is the brain misinterprets the sensation of falling asleep as actually falling, triggering a protective reflex, a throwback to when our ancestors slept in trees.

According to the Sleep Foundation: “When you fall asleep, it's suspected that a misfire sometimes occurs between nerves in the brainstem, creating a reaction that leads to a hypnic jerk”

What to do

Hypnic jerks are harmless but can be unsettling for you and your partner, if you have one. Try keeping a regular sleep schedule and cutting down on caffeine to calm your nervous system before you turn in for the night.

When to see a doctor

The occasional sleep jerk isn't anything to worry about. But if they come with flailing limbs for up to five seconds, it’s worth getting it checked out for a sleep disturbance called Periodic Limb Movement Disorder.

PLMD is linked to Parkinson's and may be treated with medications that regulate dopamine, which controls muscle movement.

Brain freeze

What is it?

A sudden pain in the forehead or temples that strikes when you quickly eat or drink something very cold.

What causes it?

It hits when cold food or drink chills the roof of your mouth, irritating the nerve endings and making the blood vessels there close quickly.

This causes rapid constriction of blood vessels in your head, which can be felt as pain in your temples.