This is a recent, and I think fairly important, paper published by Ralph Carpinelli of Human Performance Laboratory, Adelphi University: https://www.researchgate.net/public...or_Muscle_Hypertrophy_in_Experienced_Trainees The 33-page paper covers a lot of ground and is worth a look for those who take their workouts seriously. The full report is available through the link, and a pdf version can be downloaded. For purposes of brevity in this thread, following are the abstract, the table of contents, and the conclusion of the report: Abstract Researchers have expressed concern recently for standardization of resistance training protocols so that valid comparisons of different training variables such as muscular fatigue, time under tension, pre-exhaust exercise and exercise order, pyramid and drop sets, amount of resistance (load), range of repetitions, frequency and volume of exercise, interset rest intervals, etc. can be more closely studied and compared. This Critical Commentary addresses some recent review articles and training studies specifically focused on the stimulus for muscle hypertrophy in participants with several years of resistance training experience. It reveals that many of the recommended resistance training protocols have their foundation in some long-held, self-described bias. Blinding of assessors and statisticians, self-plagiarism, authorship responsibility, and conflicts of interest are briefly discussed as well. The conclusion is that most of the published peer-reviewed resistance training literature failed to provide any compelling evidence that the manipulation of any one or combination of the aforementioned variables can significantly affect the degree of muscle hypertrophy, especially in well-trained participants. Although the specific stimulus for optimal gains in muscle mass is unknown, many authors are desperately clinging to their unsupported belief that a greater volume of exercise will produce superior muscle hypertrophy. Table of Contents Abstract Hypertrophic Stimulus / Termination of Sets Drop-Set Training Time under Tension (TUT) Pre-Exhaust Training (Sequence of Exercise) Load (Amount of Resistance) Exercise Volume Interset Rest Self-Described Bias Max Muscle Plan / Science and Development of Muscle Hypertrophy Frequency of Training Text Recycling Author Contribution Terminology Pseudoscience Free Weights versus Machines Conclusion Disclosure References Conclusions Some readers may conclude that this Critical Commentary is argumentative at best. However, they may conclude also that the so-called peer review system for resistance training failed miserably to challenge the nonsense in many of these inclusive studies and reviews. It is not possible to accurately compare groups within a given study when more than one variable is manipulated or all potential confounding variables are not controlled. There is no standardization regarding the stimulus for muscle hypertrophy and consequently there are no valid comparisons of results among training studies. Most importantly, the majority of training studies (with a few rare exceptions) failed to blind the assessors. Obviously, the authors and reviewers of those studies do not believe that assessor blinding should be a requirement for non-bias reporting of outcomes. Based on all the aforementioned section summaries, this Critical Commentary concludes that there is no credible evidence for any measureable or practical intra-individual difference in muscle hypertrophy as a result of the obsessive manipulation of resistance training variables such as the number of sets, amount of resistance (load), number of repetitions, volume of exercise, interset rest intervals, repetition duration (time under tension), frequency of training, whole body or split routines, periodized and non-periodized routines, free weights and machines, etc. Based on the currently available evidence, it may be logically concluded that the few very small differences in the individual hypertrophic response to resistance training do not constitute any meaningful aesthetic differences. Any intra- or interindividual differences in muscle hypertrophy in response to manipulating different resistance training protocols probably are genetically dictated.
Exercise researchers by the name of James Krieger and Brad Schoenfeld have pretty much taken over the Internet with their studies supporting the premise that hypertrophy is principally volume driven. Almost every piece I've read online about the subject referred to Schoenfeld's and Krieger's research as being gospel. Carpinelli excoriates both their research and their reporting, declaring them substandard and misleading. While statisticians have questioned Krieger's and Schoenfeld's conclusions because of their apparent torturing of the numbers (as I have posted in other threads), Carpinelli also puts the matter into context: these guys are advocating 4 to 6 times the exercise volume for an incremental increase in muscle size of 1 millimeter over the course of their studies. Except that they don't present their findings in quite that clear a manner. Carpinelli also addresses other variables that have been associated with hypertrophy in previous studies by other researchers, as noted in the Table of Contents, and discusses the validity of those research findings.