If college guys who've lifted weights before do a specific 12-week workout plan—3 times a week, 8 exercises, 3 sets each—they'll get 25% stronger in their arms, based on how much they can lift in one...

Among men new to weight training, a workout plan that includes two rest weeks over eight weeks builds the same amount of strength in the legs and biceps as a plan with no rest weeks, even though the total amount of lifting is 18% lower.

If you're already strong and lift weights, training each muscle group either once or five times a week for eight weeks will give you about the same strength gains on the bench press, squat, and row.

After doing strength training for 12 weeks, older women—whether they started strong or weak—gained about the same amount of strength in their arms and the same amount of muscle, no matter how strong they were at the start.

Untrained young men who perform resistance training twice a week for eight weeks at moderate intensity show measurable increases in maximal strength for the bench press, bent-over row, and back squat, with strength gains ranging from 20% to 40%, regardless of how the sets are organized.

Training one arm with heavy weights three times a week for six weeks can improve the endurance of the opposite, untrained arm, allowing it to perform about 5 to 11 more repetitions in a strength test, possibly because the trained arm's increased strength influences the untrained arm.