Simple past tense and past participle of double up.
Wiktionary
Doubled-up Sentence Examples
The next morning, after church, they doubled up on Ed and rode into the hills.
The individual is doubled up with acute pains which, starting from the hepatic region, spread through the abdomen and radiate to the right shoulder blade.
Of course the hen sits with her legs doubled up under her, as does any other long-legged bird.
This was doubled up to two of each, and then redoubled in 1967 to the present four of each.
Sonya and fat little Petya doubled up with laughter.
