Summary
Highlights
The video opens by posing a question: how many arm isolation exercises are necessary for maximum muscle growth? It highlights the contrasting philosophies of bodybuilders like Arnold Schwarzenegger (many exercises) and Mike Mentzer/Arthur Jones (few to zero exercises), setting the stage for a new study that aimed to settle this debate.
A new study compared two groups of lifters. One group trained one arm with a single biceps curl and pushdown. The other group used two different arm isolation exercises from a set of three (dumbbell curls, preacher curls, incline curls for biceps; skull crushers, French presses, kickbacks for triceps), rotating them weekly. Both groups also performed compound exercises (barbell bench presses and pulldowns).
After eight weeks, muscle growth was approximately 3% in both groups, suggesting that increased arm training variety did not yield additional muscle growth. Furthermore, groups that increased training volume on isolation exercises or combined increased volume with variety also showed no significantly greater growth than the control group, which performed four sets of one exercise to failure.
The researchers themselves noted a significant caveat: the expected additional muscle growth from the increased volume (0.9%) was too small to be detected by the Dexa scans used in the study. The study also involved only six weeks of training experience for the participants and used one-minute rest intervals with training to failure, which may have limited the effectiveness of additional sets.
The study's findings, despite their limitations, align with the broader literature. Extending volume for the same exercise beyond a certain point has diminishing returns. Multiple studies have also shown that adding excessive arm exercise variety beyond one compound and one isolation exercise offers minimal additional benefit.
The video concludes with three main takeaways. Firstly, compound exercises absolutely count towards arm training volume, with fractional training volume being an ideal way to measure this. Secondly, while compound exercises are crucial, at least one good arm isolation exercise for both biceps and triceps is recommended to maximize muscle tension across the entire muscle length. However, further exercise variety beyond this provides minimal benefits.
Thirdly, performing more than 4-5 sets for a single exercise, especially when training to failure with short rest intervals, yields very little additional muscle growth. It's more effective to either move that volume to a different exercise or a different training day rather than piling on more sets for the same exercise.