Begin by standing on a comfortable surface with plenty of room.

With a a five pound potato sack in each hand, extend your arms straight out from your sides and hold as long as you can. Try to reach a full minute and then relax.

Each day you will find you can do it for longer periods of time

After 14 days, move up to ten pound sacks, then after 30 days move up to fifty pound potato sacks.

After about 60 days you will be holding a 100 pound potato sack in each hand for at least a minute.
(I’m at this level now.)

After you feel confident, put a potato in each sack.