Not progressing any more with your bench presses? Or your squats? Or other exercises? You might be interested in the study that Australian sports scientists published in the Journal of Strength and Conditioning Research. The study suggests that a temporary increase in the number of sets of a particular exercise can boost progression.
The researchers did an experiment with 32 subjects in their twenties and early thirties, who had been doing strength training for an average of seven years. All of the subjects were put through a training cycle. The schedule is shown below.
In the standardization phase all men did the same training. They covered the main muscle groups in a cycle of three training sessions, doing 4 sets of 6-12 reps for each exercise. The men trained their legs, but didn't do squats.
In the volume-manipulated phase the researchers increased the weights the subjects trained with. They used weights that were 80 percent of the weight at which they could just manage 1 rep [1RM], and trained each muscle group two times a week. This time round the men only did one leg exercise: squats. The subjects divided their muscle groups over 2 training sessions and trained a total of 4 times a week.
The researchers divided the men into 3 groups for the squats. One group did three warm-up sets and then 1 set at failure. The second group did 4 sets at failure, the third group did 8.
In the post-manipulation phase all groups did the same training again. Every time they trained their legs, the subjects did 3 sets of squats with a weight at which they could manage maximal 4 reps.
In the figure below, the period between T0 and T2 is the volume-manipulated phase, and the period between T2 and T3 is the post-manipulation phase. You can see that the group that did 8 sets of squats during the volume-manipulated phase made most progress in terms of maximal strength.
The researchers admit that the optimal number of sets for strength training is a controversial subject. Many trainers and scientists would say their 8-sets approach is too heavy, because this training stimulus does more damage than good to muscles.
The researchers are not saying they have proved that this objection is unjustified, even though their results point in that direction. "It is possible that higher volumes are associated with relatively greater central and peripheral adaptation", they write. The striking increase in strength in the 8-sets group may have been caused by the brain and nerves being given more opportunity to learn how to activate the leg muscles.
"If multiple lower-body exercises are prescribed at similarly high volumes, care should be taken to monitor possible overtraining effects", the researchers comment later in the article. "It may be that high volume schemes should be used in a cyclical manner with programs that are less physiologically demanding."
J Strength Cond Res. 2012 Jan;26(1):34-9.