Try this easy exercise

Occasionally I switch my exercise routine to a one rep maximum contraction where I get the weight into the position where the muscle is fully contracted and hold it for 45 to 60 seconds.

So when a friend sent me an email about an exercise suggested to build muscle strength in the arms and shoulders that seemed so easy she thought she’d pass it on to friends and family I was curious to read on. The article suggested doing it three days a week. I think you’ll find it useful too.

Begin by standing on a comfortable surface, where you have plenty of room at each side.

With a 5-lb 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-lb potato sacks.

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. (When she said, ”I'm at this level” I thought “No way”.)

After you feel confident at that level, put a potato in each of the sacks.

Then I realised, like you, I’d been had.