This is for older people. Younger people try it at their own risk. This is working well for me. For those of us getting along in years, here is a little secret for building your arm and shoulder muscles.
You might want to adopt this.

Three days a week - begin by standing straight, 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. Relax. After a few weeks, move up to 10-LB. potato sacks, and then 50-LB. potato sacks, and eventually try to get to where you can lift a 100-LB. potato sack in each hand and hold your arms straight out for more than a full minute. After you feel confident at that level, start putting a couple of potatoes
in the bags.