It is a pose of the man who is imitating the ape (especially gorilla's drumming).
It seems to be able to use it in the scene where the clothes that it wears when turning into the monster such as the werewolf such as the strong cry and appeal in the wild.
猿の真似(特にゴリラのドラミング)をしている人間のポーズです。
ワイルドで逞しい雄叫びやアピールに、または人狼など怪物への変身時に着ている服を破る場面で使えると思われます。

