Bending down to pick up a penny could lead to the back going out. This is a very unpleasant experience, as many of us have experienced.
The penny picker upper could have done everything right at the time to lift one tiny penny. Still, a long past exists there, perhaps, of bad habits, old back injuries, tight muscles and so on. Further, I have never heard of a very young kid hurting his or her back lifting up a penny. Why? Far less bad history, less bad habits, no prior injuries, better flexibility plus most young children squat down properly to pick up something. Watch your very young child or grandchild. See how he or she picks up a penny from the ground. Every time we act, there is a possibility of a bad outcome. There is always that risk there. We use our bodies probably more than any other tool that we have. The risk of a bad outcome, in other words, a hurting body is always there. Think about just these factors:
Young versus old
New to a task versus old hand.
High body awareness versus low body awareness
Strong versus weak
Fit versus out of shape
Flexible versus tight
Coordinated movements versus uncoordinated movements
Old injuries in a body part versus none.
Poor decisions versus common sense.
Good ergonomics (right fit) versus bad ergonomics (bad fit)
It appears that we should only have athletes that are in great shape do tasks. This should really minimize the risk. Well, in the real world it is just not possible. What we can do are things like:
Follow the rules of proper body positioning and lifting.
Rotate through different tasks
Do wellness activities (such as staying fit overall) We will still not be 100% risk free for injury because it is a complex situation with each person performing a task, but we will have come a long way in reducing the risk for injury.