Date: June 13th, 2023
The fact that training volume in bodybuilding is commonly assessed through the number of completed sets is well known, so I won't dwell on it here, just briefly remind you. Tonnage, i.e., the multiplication of lifted weight by the number of repetitions, which is used in weightlifting and powerlifting, is not the best method of volume assessment. This is due to the fact that the primary hypertrophic stimulus is created by repetitions brought to muscular failure or close to it when the muscle is sufficiently fatigued.
Hence, most scientists researching hypertrophy have settled on such a method of volume evaluation as the number of sets, of course, working ones. In 2021, a review was published titled, "Total Number of Sets as a Method of Quantitative Assessment of Training Volume for Muscular Hypertrophy".
Its conclusion was: "According to the results of this review, the total number of sets to failure or close to it seems to be an adequate method of quantitative assessment of training volume when the range of repetitions is between 6 and 20+, if all other variables remain constant".
However, a logical question arises: "How to calculate the indirect training volume? How many sets for triceps should be counted, for example, after 4 sets of bench press, and for biceps after barbell rows?"
At this point, I would like to draw your attention to the fact that all of the following applies to a lesser extent to beginners, as up to a certain point their biceps and triceps progress perfectly well from indirect loads during pulls and presses.
So, it's known that our muscles consist of several types of fibers which, for simplicity, can be divided into thin, slow and thick, fast ones. Slow fibers initially have a smaller cross-sectional area than fast ones and have significantly less hypertrophic potential.
Scientists are still hypothesizing on how this is biochemically implemented in our bodies, as known from the research: titled "The Paradox of Muscle Fiber Type and Size: Hypertrophy or Oxidative Metabolism?"
Consequently, at a certain level of muscle development, the thickest, high-threshold muscle fibers make the maximum hypertrophic contribution. Their activation, like all other fibers in the muscle, is subject to the recruitment law "Henneman's Size Principle."
That is, during the first repetition of a moderately intense set, only those fibers that are needed to overcome external resistance are involved, but as they become fatigued, the Central Nervous System (CNS), obeying the will, generates a more powerful electrical impulse, involving previously inactive fibers.
Full involvement happens 5-8 repetitions before local muscle failure, and these repetitions are called effective or stimulating.
Understanding this, one can speculate about the number of sets, or rather effective repetitions, that can be counted for the biceps during back pulls. So, let's look into a review called "Calculating Set Volume for Limb Muscles during Multi-Joint Exercises." It looks at studies comparing hypertrophy after multi-joint and single-joint exercises, but, as the authors point out, they are extremely scarce and mainly conducted on beginners.
Even in these few studies, the results are varied. In two studies, the growth of the synergist from isolated exercises was comparable to the growth from multi-joint exercises. In one study called "Single-Joint Exercises Lead to Greater Elbow Flexor Hypertrophy Than Multi-Joint Exercises," the biceps grew 50% less from rows than from forearm curls with dumbbells.
In other words, guided by the first two studies, 6 sets of pulls can be counted as 6 sets for the biceps, and the third study shows that 6 sets of back pulls can be counted as 3 sets for the biceps. Overall, over a 6-8 week horizon, which is the traditional duration of such studies, the review authors recommend counting the ratio as 1:1, which isn't exactly groundbreaking news.
Moreover, the review authors have respect for the theory of neuromuscular connection. Quote: "Bench pressing can be considered a set for the pectoral muscles, but also part of a set for the triceps and anterior deltoids. However, this likely depends on the individual and the technical execution of the exercise."
In short, until beginners learn how to push and pull with their target muscles, scientists recommend counting sets of agonists and main synergists 1:1. As for experienced athletes, they suggest evaluating the ratio based on logical justification and the athlete's personal experience.
I conducted an experiment that I would like to share with you, not understanding why scientists haven't done it yet.
Knowing that there are about 6 stimulating repetitions, I performed 6 isolated biceps curls on the Scott's machine with the maximum possible weight. Then I did a back pull for 10 repetitions to failure of the agonist, i.e. the latissimus dorsi, after which I immediately performed bicep curls. If the biceps were getting a 1:1 load, then after the pull set, I wouldn't have completed any repetitions of forearm curls. I completed 5 out of 6.
After the military press, I did lateral raises for the middle deltoids, also 5 out of 6.
After bench press, I managed to do 4 out of 6 French presses.
After leg press or squats, I didn't test the quadriceps for seated calf extension, because I don't squat, I press the platform with my "toes". Thus, doing 6 sets of shoulder presses and back pulls, specifically in these exercises, I count as 1 set for triceps and biceps, respectively.
Why I did 10 repetitions in the multi-joint exercise, rather than 6, I hope is clear, due to the obvious deterioration of neuromuscular control during high-intensity work.
As you understand, such a test can be carried out for all multi-joint exercises and, in my opinion, it will be maximally informative, for you, of course.
In short, if you are an experienced athlete, you know how to push and pull with the target muscles, then I would recommend conducting this simple test to determine the level of synergists' involvement. For most experienced people, I believe, on average, you can take the ratio of 3:1 or 4:1, and this will be close to the truth. So, don't dwell on this too much, train correctly and progress.