Incorrect manual handling techniques, lifting etc...
neck back and arm strain
Can? It might be possible but it's unlikely. Back problems are related to lifting.
Incorrect timing can cause several problems. One of which is high idling. 5000 rpm sounds high though, there may be other problems as well.
Depends on how young the child is.
Not unless you drop a weight on them while laughing.
Tie rods of incorrect length
Some common mistakes are using the incorrect grip and dominance of the bottom hand. Pressing forward can also cause problems.
7.5 with filter! Previous answer is incorrect, if you put in 8 with filter change you will be half quart over and cause problems!
Mountains would cause orographic lifting.
because lifting can cause growth to stop in your bone structure
No known connection between sexual problems and weight lifting - unless you also tried doping. Certain products are known to have detrimental side effects in that area.