The Real Driver of Muscle Growth

Barbalho, et al. separated 40 experienced female lifters into four groups. Each group trained to failure using a different amount of volume.

• Average Age: 24-25 years old
• Training Experience: At least three years
• Length of Study: 24 weeks

Note that a resistance training study done for 24 weeks is very rare. The usual is 8 to 12 weeks. We're literally looking at six months worth of training with a 100% completion rate by the subjects. That means all 40 women who started the study finished it. Fantastic.

Each group did a different amount of total sets per workout:

• 5 sets per workout
• 10 sets per workout
• 15 sets per workout
• 20 sets per workout

The program itself was done three days a week, hitting each muscle group once a week.

Monday Training

• A. Barbell Bench Press
• B. Incline Barbell Press
• C. Barbell Military Press
• The 5 set group did 2 sets of bench presses, 2 sets of inclines, and 1 set of military presses.
• The 10 set group did 4 sets of bench presses, 4 sets of inclines, and 2 sets of military presses.
• The 15 set group did 5 sets of bench presses, 5 sets of inclines, and 5 sets of military presses.
• The 20 set group did 7 sets of bench presses, 7 sets of inclines, and 6 sets of military presses.

Thursday Training

• A. Lat Pulldown
• B. Cable Row
• C. Upright Row
• The 5 set group did 2 sets of pulldowns, 2 sets of cable rows, and 1 set of upright rows.
• The 10 set group did 4 sets of pulldowns, 4 sets of cable rows, and 2 sets of upright rows.
• The 15 set group did 5 sets of pulldowns, 5 sets of cable rows, and 5 sets of upright rows.
• The 20 set group did 7 sets of pulldowns, 7 sets of cable rows, and 6 sets of upright rows.

Friday Training

• A. 45-Degree Leg Press
• B. Barbell Squat
• C. Stiff Legged Deadlift
• The 5 set group did 2 sets of leg presses, 2 sets of squats, and 1 set of stiff legged deadlifts.
• The 10 set group did 4 sets of leg presses, 4 sets of squats, and 2 sets of stiff legged deadlifts.
• The 15 set group did 5 sets of leg presses, 5 sets of squats, and 5 sets of stiff legged deadlifts.
• The 20 set group did 7 sets of leg presses, 7 sets of squats, and 6 sets of stiff legged deadlifts.

The scientists periodized the training so that the lifters used different rep schemes each week. Then they rotated back around each month:

• Week 1: 12-15 reps, 30-60 seconds rest between sets
• Week 2: 4-6 reps, 3-4 minutes rest between sets
• Week 3: 10-12 reps, 1-2 minutes rest between sets
• Week 4: 6-8 reps, 2-3 minutes rest between sets

This periodization model was repeated six times (there's your 24 weeks).

The researchers tested the women's 10-rep max on the bench press, lat pulldown, leg press, and stiff-legged deadlift at the beginning of the study. The scientists also measured muscle thickness of the biceps, triceps, pecs, quads, and glutes. The tests and measurements were repeated after 24 weeks. This is what they found:

• All groups showed significant increases in all muscle thickness measurements and 10-rep max tests.
• There were no differences in any 10-rep max tests between the 5 and 10 set groups.
• The 5 and 10 set groups showed significantly greater 10-rep max increases for lat pulldowns, leg presses, and stiff-legged deadlifts than the 15-set group.
• For the bench press, the results from the 5, 10, and 15 set groups didn't differ significantly, but the 20-set group tested out the worst. In fact, 10-rep max changes for the 20-set group were lower than all other groups for all exercises.
• As for muscle thickness improvement, as you might expect, it correlated with the strength gains. The 5 and 10 set groups showed significantly greater increases than the 15 and 20 set groups in all measured sites.
• Muscle thickness increased more in the 15 set group than the 20 set group in all sites. The increases in the 5-set group were higher than the 10 set group for the pecs, whereas the 10-set group showed higher increases in quadriceps muscle thickness than the 5-set group.

To put this in perspective, the 20-set group exhibited about a quarter of the gains that the 10 set group did.

The one argument against this study is that the subjects in the 15 and 20 set groups probably did too much volume in their sessions and exceeded their capacity to recover. If the work load had been spread out over more training days in the week, the outcome could have been different.

Nice try, but they didn't exceed their maximum recoverable volume in a single session! Look at the following sentence, taken straight from the study:

"All groups significantly increased in all muscle thickness measurements and 10-rep max tests at the end of the 24 weeks."

All the groups improved in strength and size by the end of the 24 weeks. If the 15 and 20 set groups were exceeding their "maximum recoverable volume in a single session," they sure as hell wouldn't end up with gains after six months of doing it every week. So that argument doesn't hold up at all.

Still, it should give you pause. Just because you're making progress, it doesn't mean you're training optimally. This study is a clear-cut case where doing less meant gaining MORE.

Some of you wanna-be overachievers might ask, "How would you change their program so that I'm hitting a muscle group twice a week?"

I wouldn't. To me, this study represented a large enough sample size with enough volume variations to see that some awesome strength and size gains can be made by training three days a week and hitting each muscle once during that training week.

The real-world anecdotal evidence tends to back this up. You can indeed train just three times a week, hitting a muscle once during that week, and make outstanding progress.

When I eyeballed this study (along with literally a dozen others while researching this article), I saw a program that looked exactly like the kind of training I did as an intermediate and used to make awesome progress: A total of about 10 sets per body part, once a week.

Novice lifters often get caught up in overanalyzing every nuance related to training (especially in studies) and forget a very simple principle: If you want to grow, then you're going to have to be moving more weight for more reps six months from now.

That's what we saw here. The ones who increased their rep strength the most, grew the most. The driver was progressive overload. Not volume.

The other takeaway from this should be that your effort in the gym is what dictates volume – not establishing some arbitrary number of sets to be done and then down-regulating your effort to meet that number. That's literally how people end up doing junk volume.

Train your ass off. Beat rep PRs. Grow. It's that simple.

1. Barbalho M et al. Evidence for an Upper Threshold for Resistance Training Volume in Trained Women. Med Sci Sports Exer. 2019 Mar;51(3):515-522.