Modifying Set Numbers: 1, 3, or 5 Sets - How Many Shall We do per Exercise in 2015? First Study to Investigate Potential Benefits of 5 Sets in the Long (6 Months) Run

I have to admit. I am surprised that the total lean mass didn't but the sleeve size of the subjects did benefit from increasing the number of sets from 1 to 3 and from 3 to 5 sets. For legs this would have been something I would have expected. For arms, which are trained with almost every other exercise? No, not really.

With their latest study, scientists from the University of Rio Grande do Sul, the University of Wisconsin-Eau Claire and the Federal Universities of Rio de Janeiro and Maranhão tried to fill the gap that exists with respect to studies comparing the effects of multiple sets, greater than 3-sets, on strength and muscle hypertrophy over long training periods. Accordingly, the aim of the study was to compare the effects of 1, 3 and 5-sets on the changes in the muscle strength and endurance, muscle hypertrophy, vertical jump performance and body composition over the course of a six months standardized training regimen.

The hypotheses of the study was that multiple sets would result in greater changes in training outcomes than single sets and that there would be a dose response for training outcomes.
In view of the fact that the subjects were 48 men from the Brazilian Navy School of Lieutenants (mean ± SD age = 24.4 ± 0.9 yrs; body mass = 79.3 ± 9.1 kg; height = 174.5 ± 5.5 cm) who were familiar with all sorts of body weight "strength training" drills, but had not trained on any of the Life Fitness machines that were used in the study, it's not unlikely, though, that even one set of bench presses, leg presses, lat pulldowns, leg extensions, leg curls, biceps curls, ab crunches and triceps extensions, which were performed thrice a week, would suffice to produce significant results (also compared to the regular military training the men in the control group performed).

Figure 1: Overview of the 6-week resistance training protocol used in the study at hand.

All exercises were performed with a weight of 8-12RM (meaning the subjects failed after 8-12 reps) and a rest interval of 90 to 120 seconds between sets and exercises. The training resistance was increased by 5-10% for the next session when subjects were able to perform more than 12 repetitions in all sets of an exercise.
The scientists made sure that all subjects participated in at least 95% of the training sessions (missed no more than four sessions). All training sessions were monitored by an experienced investigator and the subjects were not allowed to perform aerobic or flexibility exercises during the six month training period. What the scientists found was:

• Figure 2: Changes in body composition (top) and bench press & lat pulldown 5RM (Radelli. 2014).

  All training groups recorded significant strength gains for bench press (BP), front lat pull down (LPD), shoulder press (SP) and leg press (LP) (p≤0.05) exercises, but the 5RM (maximal weight the subjects could lift 5 times) increased significantly more for both bench presses and lat pulldowns in the 5- SETS compared to the other training groups (p ≤ 0.05). 
• In the 20RM (maximal weight with 20 reps) bench press tests both the 3- and 5-SETS groups saw significantly greater strength increases than the 1- SET group, with the 5-SETS protocol also producing significantly greater increases in strength, than the 3-SETS group (p≤0.05). 
• In the 20RM leg press tests only the 5-SETS protocol yielded significantly greater strength gains than the 1-SET protocol. 
• For the 3- and 5-SETS groups the scientists also observed significant increases in elbow flexor muscle (biceps) thickness (MT) with the 5-SETS increase being significantly greater than the other two training groups (p≤0.05). 

In spite of these differences, all training groups decreased percent body fat, increased fat free mass and vertical jump ability (p≤0.05), with no differences between groups. In spite of that, "the results demonstrate a dose response for the number of sets per exercise and a superiority of multiple sets compared to a single set per exercise for strength gains, muscle endurance and upper arm muscle hypertrophy" (Radelli. 2014).
References:

• Bottaro, M., et al. "Resistance training for strength and muscle thickness: effect of number of sets and muscle group trained." Science & Sports 26.5 (2011): 259-264.
• Hanssen, K. E., et al. "The effect of strength training volume on satellite cells, myogenic regulatory factors, and growth factors." Scandinavian journal of medicine & science in sports 23.6 (2013): 728-739.
• Radaelli, Regis; Fleck, Steven J.; Leite, Thalita; Leite, Richard Diego; Pinto, Ronei S.; Fernandes, Liliam; Simão, Roberto. "Dose Response of 1, 3 and 5 Sets of Resistance Exercise on Strength, Local Muscular Endurance and Hypertrophy." Journal of Strength & Conditioning Research: Post Acceptance: December 24, 2014. doi: 10.1519/JSC.0000000000000758
• Rønnestad, Bent R., et al. "Dissimilar effects of one-and three-set strength training on strength and muscle mass gains in upper and lower body in untrained subjects." The Journal of Strength & Conditioning Research 21.1 (2007): 157-163.