Just came across this exercise suggested for senior citizens to build muscle strength in the arms and shoulders. It seems so easy that I thought I'd pass it to some of the younger folks. The article suggested doing it three days a week. Begin by standing on a comfortable surface where you have plenty of room at each side. With a 5-pound potato sack in each hand, extend your arms straight out from your sides and hold them there as long as you can. Try to reach a full minute, then relax. Each day, you'll find that you can hold this position for just a bit longer. After a couple of weeks, move up to 10-pound potato sack. Then 50-pound potato sacks, and eventually try to get to where you can lift 100-pound potato sack in each hand and hold your arms straight for more than a full minute. After you feel confident at that level, put a potato in each of the sacks.