23/10/2022
Training a muscle 3x per week doubles muscle growth compared to training it 1x per week, new study on trained lifters finds
I had been waiting so long for this study on training frequency.
The researchers compared the effect of training a muscle 1x vs. 3x per week for strength and muscle growth using a within-subject design. This is much more robust than the typical between-individuals design, as you control for each person's individual genetics, diet and lifestyle.
The trainees performed one-legged leg presses. One leg did 9 sets once a week. The other leg did 3 sets 3x per week.
A second group did the same program but equalized total training volume work (sets x reps x weight) between frequencies.
Since you can normally perform considerably more work with higher training frequencies due to being less fatigued, the 3x per week group had to hold back to perform only the same volume as the 1x per week group.
When equating total training tonnage between groups, there were no meaningful differences between the training frequencies, as expected based on prior research. In contrast, the leg trained 3x per week without holding back achieved 2-2.7x more muscle growth than the legs being trained 1x per week group (4.1% vs. 1.5% & 2.1% increases in quad CSA). In other words, it seems the higher training frequency more than doubled their size gains.
Leg press 1RM strength increased 25% in the 3x leg compared to 16% & 19% in the legs being trained once per week.
However, none of these differences were statistically significant. With only 12 lifters per group, trained individuals and a 9-week study, statistical power was most likely too low to detect any realistic effects as statistically significant. So the authors performed an effect size analysis. This indicated the effect of training frequency was insignificant when equating total work but of medium strength when not equating total work. The confidence intervals of the between-group effect sizes for both strength and size did not cross zero in the comparison not equating total work, indicating it was very likely that the difference was real and of meaningful practical importance. Put simply, the data showed training a muscle 3x per week can in practice considerably improve strength development and muscle growth compared to traditional bro splits that train each muscle only 1x per week.
For more information, check out the section 'The benefits of high frequency training' in this article: https://mennohenselmans.com/high-resistance-training-frequency-enhances-muscle-thickness-resistance-trained-men/
