The single set (or one set) indicates the execution of only one working set per exercise. The origins of the single set date back to the 1920s, but it was strongly promoted in bodybuilding since the early 70s thanks to the training method for hypertrophy High Intensity Training (HIT) by the entrepreneur Arthur Jones, later reworked by Mike Mentzer under the name of Heavy Duty™ (HD).
Jones claimed that a single set at maximum intensity per exercise was sufficient to optimize hypertrophy, and that more than one would not provide better results, even increasing the risk of overtraining. Jones’ disciple, Mike Mentzer, carried on this philosophy by re-proposing it in his Heavy Duty™.
Both the didactic and recreational approaches to resistance training for hypertrophy and strength support the superiority of multiple sets (more than one per exercise), and in fitness-bodybuilding it was established the dogma that at least three sets are required to optimize the stimulus induced by a single exercise.
But the meaning of single set and its contextualization are ambiguous, and a deepening into the topic may better serve to understand its possible use in modern and evidence-based bodybuilding programs.
Contextualize single sets
It seems that the single set system was formalized in the 1920s by the American strongman Earle Liederman: his method consisted of performing a heavy exercise with low repetitions and 5 minute rest between exercises (1). The single set also became a peculiar feature of the circuit training, introduced by Morgan & Anderson in 1953, a total body protocol where the single set exercises are performed one after another without, or with very short rests (15-30 sec) (2).
Jones resumed the concept of single set only in 1970, but his method was based by definition on high intensity of effort and wasn’t necessarily based on performing a single set per muscle, but often to perform only one set per exercise (3). In other words, the total volume for the muscle (muscle-specific volume), although quite low, often did not include only one set.
In Jones’ protocols, the weekly volume was more often maintained between 2 and 4 sets, even going up to 6 weekly sets per muscle, covering part of this volume with single sets (3). Therefore, single sets do not mean only one set per muscle in the microcycle (week) or in the session, but they mean single sets per exercise even if the muscle-specific volume in the microcycle or session is 3-4 times higher and multiple sets are also present.
For this reason, the inherent effect of single set must be distinguished from that of low set volume per muscle in the microcycle. The single sets could also be used in high-weekly volume programs, just as multiple sets may be the only choice with a low weekly volume. This distinction is important as single sets are always associated with very low volumes or one set per muscle regardless.
Arguments supporting multiple sets
The didactic and technical approach to resistance training promotes multiple sets (per exercise) for various reasons. One of the main and most trivial is to optimize the motor pattern of complex exercises, usually multi-joint free-weights. That’s because volume determines the amount of practice developed on an exercise, and since strength is specific to a movement, the more time is spent practicing an exercise, the stronger and more skilled one will become on it (4).
This is especially important for complex movements since the time required to make them productive for hypertrophy would be longer than for simple movements (such as single-joint exercises) (4,5). A leg extension will be immediately efficient for hypertrophy, while a squat will take a long time to develop the correct motor pattern, use loads (and efforts) proportionate to the true strength of the agonist muscles, and make it equally efficient for hypertrophy (4).
Since hypertrophy programs generally include free-weight multi-joint exercises for a large part, opting for multiple sets per exercise (logically at least three) would be a better choice to make those same exercises more productive and in the shortest time as possible.
Another lesser-known reason in support of multiple sets is the better development of fatigue resistance over the course of the sets, and therefore of the efficiency in accumulating repetitions for the planned sets of the same exercise (6). Performing a single set exercise certainly improves strength in the single set, but prevents that strength from being maintained as best as possible in subsequent sets to accumulate more reps and volume load (total tonnage) (6). Since the volume of repetitions and load affect hypertrophy, this quality is important, even more so with a low set volume.
Arguments supporting single sets
In the 1970s, a time of the full development of bodybuilding, single sets had been popularized by Arthur Jones through his very low volume (HIT) protocols, where muscle-per-workout sets varied roughly between 1 and 5 (3).
This volume could be covered both by exercises performed in a single set and by 2-3 multiple sets. Jones, therefore, did not promote the exclusive use of single sets as often claimed, but just meant them as a preponderant and countercurrent modality.
Single sets were perhaps also justified to ensure a variety in the exercise selection. Doing such a low volume with a single exercise with multiple sets wouldn’t have allowed the selection of movements of a different nature, a principle still considered valid today (4). Single sets would therefore have served to better respect this principle where the multiple sets would have hindered it.
Single sets are very compatible with the HIT also because Jones preferred machines, a category of exercises that, as mentioned above, requires much less (if any) motor learning before becoming productive for hypertrophy. Jones in fact designed the Nautilus machines specifically for the single sets mode (many accused him of having created the method to sell his own machines), and from a scientific perspective today it’s possible to say that this choice makes sense.
Likely one of the main objective benefits of single sets may be psychological, facilitating the achievement of maximum intensity of effort (muscle failure or above) if that’s required. It’s now well documented that even trained subjects underestimate the maximum repetitions (RM) to reach failure (7,8); the idea of facing only one set would predispose to express the real maximum intensity, while the idea of facing 3-5 sets of the same exercise to failure will likely make easier to underdose it.
The single sets are also accepted by the most important organizations and reference authors, but it’s contented that their usefulness would be limited to untrained in the early weeks of training, or to classic circuit training typically structured in this way (which in any case is not optimal for hypertrophy) (1).
The fallacies about single sets
Jones and Mentzer repeatedly stated that more than one set per exercise would have no additional effect on muscle growth, even increasing the risk of overtraining (9,10). Yet, in Jones’s programs, there were often 2-3 multiple sets per exercise or at least more than one set per muscle (3).
One of the ideas seems to be that the maximum intensity of effort would have been expressed only in the first set, while in the following a decrease in repetition maximum (RM) would have occurred (1). However, trained bodybuilders with a well-developed muscle endurance may be able to repeat several multiple sets while maintaining the same number of repetitions to failure set after set (1,11), although short rest periods typically prevent this (12). Furthermore, the fatigue accumulation lowers failure threshold and recruitment threshold of type 2 fibers (13), so it is a problem that from this point of view would not arise, since the maximum intensity and recruitment can still be reached even if RMs go down set after set.
The fact that multiple sets (or even low-medium volumes) expose to overtraining is a “theory” that current research does not confirm (14), but a further error was probably the misuse of the term that still today is commonly done in sports. What is improperly defined as “overtraining” would actually be a response to acute fatigue due to short phases of intensified training, but in the current literature it does not appear that a few sets at high-intensity of effort are sufficient to cause it (14), and above all, that this impairs hypertrophy development.
It should also be considered that detecting the failure threshold is harder with high repetitions (15) (and therefore long time under tensions), so the supposed “psychological advantage” of single sets would not be actual with high intensities of load (6-8 RM), but rather with low intensities (≥12 RM). In other words, a single set with high loads would likely not confer a greater advantage in reaching failure, a threshold that in any case, would be better not to reach at high intensities of load (4).
Jones’s philosophies were first emphasized by Mike Mentzer in the 1980s, then carried out in recent years by some researchers who strongly supported the method (9,16,17). Unsurprisingly, many of the narrative reviews and opinion papers that emphasized the philosophies of Jones and Mentzer were criticized by other scientists for being highly flawed and in conflict with the evidence (10,18,19,20). The empirical evidence and the current scientific consensus in fact point to quite other directions.
Research on single set and hypertrophy
In research, the issue about single vs multiple sets found a major turning point in 2010 with the meta-analysis by James Krieger. Analyzing the literature published up to that time, the author found that multiple sets protocols per exercise favored more hypertrophy than a single set per exercise (21). It should be noted that the analysis evaluated the volume per exercise in the single session and not the set volume per muscle in the entire week/microcycle.
In 2017, Krieger himself was co-author, together with Brad Schoenfeld, of another meta-analysis to investigate the effect of weekly set volume per muscle on hypertrophy. The results showed that 10 or more sets per week per muscle doubled the hypertrophy response compared to 5 or fewer weekly sets (22). Exploring the optimal set volume thresholds for hypertrophy departs from the scope of the article, but this shows that the very low volumes as promoted by Jones and Mentzer, represented largely by single sets, are not a good choice for maximizing hypertrophy.
However, that does not invalidate the use of the method regardless. In an experimental context, the inherent effect of single sets could be understood by matching the total set volume, in one group performing only a few exercises with multiple sets, while in the other group performing the same number of sets per muscle by performing one set for each exercise always different. For example, 2 exercises of 3 sets each, compared to 6 exercises of 1 set each.
But even in this case, the extrapolations would be unrealistic and dichotomous, since the single set can be used in just 1 or 2 exercises in a workout predominant in multiple sets. In fact, the research does not seem to answer the question of whether performing 1 or 2 exercises in a single set mode could be an equally optimal alternative choice compared to multiple sets alone, when the total set volume is matched.
Recontextualize the single sets
Today single sets are a rather abandoned modality in bodybuilding, likely because always associated with HIT/Heavy Duty™, whose old theories are in stark contrast both with the most advanced training methods for natural bodybuilding, and with the parallel school of high volume already prevailing in doped bodybuilding community in the golden age of Jones himself.
All the more reason, modern natural bodybuilding has seen a growing influence of powerlifting and general strength & conditioning, mostly based on free-weight compound movements and complex skills that require frequent repetition to refine motor patterns and performance, having to rely on multiple sets per exercise.
But these positions are dichotomous since performing a single set doesn’t strictly mean sacrificing multiple sets, much less the high volume or with the use for highly complex exercises. Rather, a single set can be viewed as an additional tool in hypertrophy programs, even in a high volume context. There is no reason to believe that a single set for one exercise is not or less productive when implemented into workouts with optimal volume and a predominance of multiple sets.
Exercise selection: The single set is suitable for exercises characterized by simple movements (more often single-joint and/or fixed-plane machines), and it’s not for those complex exercises where the multiple sets provide a significant contribution to learn or refine the motor pattern and become stronger and skilled at executing them.
Intensity of effort: The technique is ideal for high intensity of effort (muscle failure or intensity techniques) thanks to the typical “psychological advantage” in facilitating the expression of maximum intensity in the single sets. The intensity techniques are those that allow you to overcome the normal muscle failure (stripping, rest-pause, agonist super set, burns, etc.). In this way, a single set could be the ideal opportunity to understand the real meaning of maximal or supra-maximal intensity of effort.
Intensity of load: Due to the points above, single sets would not be well compatible with high intensities of load in the hypertrophy range (6-8 RM), as these are more suitable for multi-joint exercises requiring multiple sets, and where it is most prudent to avoid muscle failure. Furthermore, the “psychological advantage” in reaching true failure is best exploited with low intensities of load due to the greater difficulty caused by the typical burning of the glycolytic metabolism.
Exercise order: Again due the points above, the high intensity of effort single sets would be better placed in the last exercise of the part dedicated to the target muscle, to prevent the high fatigue accumulated with a high intensity of effort compromising the performance in the subsequent exercises; in other words, it would goes well with finisher exercises.
Periodization/programing: The single set can be kept stable over the mesocycle, or it can be used as an accumulation and/or intensification technique in the functional overreaching phases, representing an additional stressor only within more stressful microcycles;
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