Counting runs you the risk of repetitive stress injury, so the Annals of Physical Anthropology reported on a Japanese study that explored the best way to count money.
The researchers studied the speed of counting, along with the strain on 14 different muscle groups. Here's their advice:
For maximum efficiency and the least risk of repetitive stress injury, you should keep your upper arms close to your body and your forearms extended at an angle of 30 degrees. This seems to be the best position all around for the arms, back and shoulders, and also allows for the fastest counting rate.
In addition, the work surface should always be below elbow level, and you should never sit more than 19.6 inches from it.