There is a difference between someone in their 20’s and someone 40 plus lifting weights. The report states that middle age people who try the traditional lift heavy for 3 sets injure themselves after a few weeks and quit.
They should always do just one set. Only when they can lift that weight at least 20 times in a row and not feel sore the next morning, should they increase the resistance by going to the next heavier weight.
The key to this program is to avoid injuring their muscles by lifting weights in a single set and increasing the number of repetitions gradually so they do not cause next-day muscle soreness. They should not increase the weight (resistance) until they can lift a set of at least 20 daily and not feel sore the next day.
Before any older or out-of-shape person starts an exercise program, he or she should check with a physician to rule out serious problems that might be aggravated by weight lifting.