A little resistance training

If you are using resistance training as part of your fitness or performance training routine this may help you with the question; How many sets?

If you're training for general health then 1 set per exercise is adequate. I'll define general health as not working to achieve maximal strength gains. For example one set of lat pull downs, chest press, leg press, etc to keep tone.

If you are working to reach maximal strength gains, then 1 to 3 sets of each exercise is recommended. Some studies indicate that when doing more than 3 sets per exercise a person will not receive any more benefit than a person doing 2 to 3 sets. However, everyone is different and you may find you will achieve more strength with more sets.

Additionally using a non-linear program may increase maximal strength more than a linear program. For example a linear program is 3 sets of 10 reps at 75% of 1RM done 3 to 4 days a week. A non-linear plan may look like this 3 sets of 2 repetitions [reps] at 90% of 1RM on Monday, 3 sets of 6 reps at 85% on Wednesday and 3 sets of 7 reps at 60% on Friday.

Be sure that you are aware of the volume you lift each day. The volume or total load [weight] lifted for 3 sets of 2 at 90% of 1RM on Monday when the 1RM is 100 is 3 x 2 x 90 = 540 total volume, on Wednesday, 3 x 6 x 85 = 1,530 and on Friday is 3 x 7 x 60 = 1,260 of total load or weight per exercise. So the heavy day is Wednesday. It's not on the day you lift 90% of 1RM as may people mistake, including some coaches.

Go hit the weights (but you may want to hire a coach to be safe)!