Eli5 why grown ups do not fall down from the bed?

Question

I am wondering why small kids ( even a few years old) fall down from the bed while changing their position but bigger children /adults do not, no matter how much they move while sleeping?

In: 2276

Answer 1

I have slept in a king size bed for the past 38 years. Last year, I had to sleep in a twin bed for a week. On one of those nights I managed to fall out of bed while asleep. Luckily I landed on my hands and knees. Laughed about it in the morning. I was 59 at the time.