An observation that is contrary to my understanding of mechanics:
Consider me lying on my back. Trying to lever up my upper body will lift my legs up
(the dot being my butt, as the fulcrum of movement)
Now if I bend my knees I can lift my upper body without my feet leaving the floor
But… shouldn’t it be the other way round? With bent knees the leverage that the weight of my legs can exert as a counterweight is less, so it should be in the bent-leg position rather than the extended-legs position that my feet leave the grounds.