Not all weightlifting exercises are equal — exercises that work multiple muscles at once (like squats) should count as half a set when predicting muscle growth, because they help but aren’t the main target.
Scientific Claim
In young, mostly male adults, the effects of resistance training volume and frequency on muscle hypertrophy and strength are best understood when indirect sets (e.g., compound movements) are weighted differently than direct sets, improving predictive accuracy of training outcomes.
Original Statement
“Distinguishing between direct and indirect sets appears essential for predicting adaptations to a given resistance training protocol, such as using the 'fractional' quantification method.”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
association
Can only show association/correlation
Assessment Explanation
The claim describes a methodological finding based on statistical model comparison, not causal inference. The language is precise and aligns with the study’s own conclusions.
Evidence from Studies
Supporting (1)
The Resistance Training Dose Response: Meta-Regressions Exploring the Effects of Weekly Volume and Frequency on Muscle Hypertrophy and Strength Gains
This study found that when you count exercises like squats (which work many muscles) differently than isolated moves like bicep curls, you can better predict how much muscle and strength you’ll gain—exactly what the claim says.