For those keyboard jockeys (those with jobs that require sitting at a computer all day) that don't want to spend the money for those fancy exercise machines, here is a little secret for building arm and shoulder muscles. Three days a week works well.
Begin by standing (in your cubicle works well) with a five pound potato sack in each hand extend your arms straight out to your sides and hold them there as long as you can.
After a few weeks, move up to ten pound potato sacks and then fifty pound potato sacks, and finally get to where you can lift a one hundred pound potato sack in each hand and hold your arms straight for more than a full minute.
Next, start putting a few potatoes in the sacks, but be careful not to overdo it.