According to conventional wisdom, training for maximal strength requires low reps (1-5) and heavy weights, while muscle size is best achieved with slightly higher reps (6-12) and lighter weights.
There’s more to the story, though, as a recent study by researchers from the University of Central Florida shows. They put a group of 33 resistance-trained men through eight weeks of strength training. The subjects were divided into two groups:
The first group did 4 sets of 10-12 reps, resting for 1 minute between sets.
Group two did the same exercises. They also did the same number of sets. But they used a much heavier weight that limited them to 3-5 reps, taking around 3 minutes of rest between sets.
Short sets of 20 seconds or less may well develop strength, but they’re not supposed to be as effective when it comes to muscle growth as sets lasting 40 to 60 seconds.
So you’d expect the group lifting the heavier weights to gain the most strength, while subjects training in the so-called “hypertrophy zone” would gain the most size.
But that isn’t what happened.
With the exception of the increase in arm mass, which was twice as great in the heavy lifting group, none of the differences in body composition between the groups were statistically different. However, the researchers did find a clear trend towards greater gains in the group lifting heavier weights.
In other words, the men training in the 3-5 rep range were the ones that built the most muscle.
What about strength?
The guys lifting in the 3-5 rep range gained significantly more strength in the bench press. The weight they could lift once rose by 14%, more than double the change seen in the higher rep group. Their bench went up by an average of 6%.
Both groups gained strength in the squat, with no significant differences between the two.
Here’s how the researchers sum up the results:
“The results of this study indicate that high‐intensity (3–5 RM), low‐volume resistance training program utilizing a long rest interval (3 min) is more advantageous than a moderate intensity, high‐volume (10–12 RM) program utilizing a short rest interval (1 min) for stimulating upper body strength gains and muscle hypertrophy in resistance‐trained men during an 8‐week study.”
So, what does all of this mean for you?
Well, it doesn’t mean that training in the 3-5 rep range should now be considered superior to everything else when it comes to building size and strength.
For one, there was no intermediate rep range. It would have been interesting to see what have had happened had a third group been involved, lifting in the 5-8 rep range.
Nor does it tell us if a combination of heavy and light loads would have delivered better results.
There is some research to suggest that lighter weights and higher reps promote greater gains in type I muscle fibres. Heavier weights and lower reps, on the other hand, may increase growth in the type II fibers to a greater extent.
From Dr Brad Schoenfeld:
“If your goal is to build as much muscle as possible, it seems appropriate to train across the spectrum of loading zones; use lighter loads to target type I fibers and heavier loads to target type IIs. In this way, you ensure maximal development of all fiber types.”
Of course, this is far from being the last word on loading zones and muscle growth. But the findings do add to a pattern of results suggesting that the range of repetitions you can use to gain muscle is a lot wider than previously thought.
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ABOUT CHRISTIAN FINNChristian Finn holds a master's degree with distinction in exercise science, is a former personal trainer and has been featured on BBC TV and radio, as well as in Men's Health, Men's Fitness, Fit Pro, Zest, and Perfect Body magazine.