Book 33, Question 95
How can sloths hang upside down for hours?
A sloth has long, curved claws like hooks, and strong arms.
Special tendons in its fingers lock so it can hold on without using much energy. It doesn’t have to squeeze its muscles all the time. Because of this, a sloth can rest while hanging for a long time. It moves slowly and saves energy. A sloth is a champion of hanging.