Up to 60% of adults experience the occasional nocturnal leg cramp, which can feel like a painful spasm, tightening or twinge. They develop when the nerves that carry signals to your muscles fire off too many messages at once.

This causes your muscles to contract in an uncomfortable way, says Dr Scott Garrison, director of the department of family medicine at the University of Alberta.

Read more: Make a muscle cramp vanish

Sitting or lying down for a long time – like when you’re sleeping – can trigger the nerve malfunction. That’s why you tend to get cramps in the middle of the night. And weirdly, these cramps are more common in warmer months, according to a study from Dr Garrison and his team.

It might be because you have higher levels of vitamin D in the summer, thanks to increased sun exposure. The nutrient plays a role in regulating the growth and repair of your muscle fibres, says Dr Garrison.

But more growth and repair may also send the muscle mechanism behind your cramps into overdrive, he says.

Read more: Is muscle soreness really a sign of an effective workout

Nocturnal leg cramps become more common – and painful – as you age, says Dr Garrison. After you hit 50, you start losing more of the nerve cells that send messages from your brain to your muscles. The cells that are left have to work harder, which experts speculate might cause cramping.

Fortunately, the spasms are usually harmless. But in rare cases, they can signal electrolyte imbalance or neuromuscular disorders like amyotrophic lateral sclerosis (ALS), known as Lou Gehrig’s disease.

Stretching your calves, hamstrings and quads before bed will stop cramps before they start. In fact, a 2012 study from the Netherlands found that older adults who suffered from these cramps experienced fewer, less severe spasms when they stretched their legs for three minutes prior to hitting the sack.

Read more: This is what would happen to your muscles if you stretched for 10 minutes every day

If a spasm does strike in the middle of the night, ease the pain by using the same stretches. Your usual first line of defence – hopping out of bed and walking around for a minute – will help relieve tightness, too.

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