So how come if you push a car, you don't align your bones? Elbows, knees, hips are all bent to some degree. Why is this the most efficient way? After all, pushing a car is just the reverse problem of being pushed by a car.
Well, you do align your bones. If you've ever pushed a car, or watched someone do it, you see them get into a steep position to start pushing. This steep position lines up the bones/structure of the body with the force of the car. This enables us to use weight and alignment to help us.
The joints bend to help the muscles apply active force to the object we want to move. We bend our knees to extend our legs to move the car.
In the receiving a push discussion we are talking mostly about passive resistance. In the car pushing example, we are talking about very active pushing. The muscles propel the car forward when we move the car. The muscles hold the alignment when we are receiving force.
You are correct, similar, but slightly different. In either situation alignment helps greatly.