I came across this exercise suggested for seniors to build muscle strength in the arms and shoulders. It seems so easy, so I thought I'd pass it on.
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 five-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 a 10 lb. potato sack.
Then 50 lb. potato sacks and then eventually try to get to where you can lift a 100 lb. potato sack in each hand and hold your arms straight for more than a full minute.
Once you feel confident at that level, put a potato in each of the sacks