The debate about the number of optimal series to gain strength has long since stopped taking into account the option of a single series per exercise. However, there are still systems that advise it, some of them recently created. From my point of view, this can only be due to two reasons: Lack of knowledge or commercial interest to offer a system as novel or revolutionary when it lacks the scientific basis to back its arguments.
One of the first to propose single-sets per exercise was Arthur Jones, the founder of Nautilus and MedX, at the beginning of the 70s. Due to the scarce scientific literature existing at that time, based on the reasoning that justified it and forgetting the reasoning that suggested just the opposite, it could make sense. The difference is that more than 40 years have passed since then, specialized scientific journals have proliferated, and now universities devote many more resources to studying performance, consequently accumulating scientific literature that allows us to have things clearer. It is also important to note that Arthur Jones never published his postulates in a scientific journal.
A few weeks ago, he published an article about what we really know today about what really works to gain muscle mass. One of the points was precisely the volume or number of series per exercise, training day and week where he cited references that showed that doing more than one series per exercise increased effectiveness when the goal was to gain muscle mass. On this occasion I will deal with this same topic when the objective is the development of force.
First of all, it is important to emphasize that in training strength, power or hypertrophy, to pay attention to a single study is meaningless since each method used takes into account a configuration of the training variables (exercises, repetitions, series, intensity, muscle failure, volume, rest, …) different, which radically affects the results. For this reason, we must pay attention to systems that cross the information of a large number of studies, with different methodologies and results, so that the conclusions are minimally rigorous. This type of studies are called systematic reviews or meta-analyzes and constitute the highest level of existing evidence, that is, the highest credibility within the scientific literature.
Well, the different meta-analyzes that have been carried out in the last decade obtain different results, some more pronounced than others, due in large part to the reasons explained above. However, all of them have seen better results when more than one series has been used per exercise. Because each published meta-analysis takes into account all previously published studies, including those conducted since the last meta-analysis, as long as it is well designed, the most recent one will generally be more reliable. The magazine where it is published is also important since not all of them have the same control mechanisms on the veracity of what they publish.