One study with women showed a much bigger muscle growth difference than the others — all of which were only with men — suggesting sex might matter, but we need more studies to know for sure.
Scientific Claim
Sex may influence the response of type II muscle fiber hypertrophy to resistance training load, as one study including females showed a substantially larger effect size (SMD=1.01) compared to others, which exclusively included males.
Original Statement
“Specifically, the SMD from this study amounted to 1.01, which is substantially higher than the effects observed in other studies. This study differed from other research by the inclusion of females as study participants. All other included studies utilized samples comprised exclusively of males. Tentatively, these results may indicate that training with low and high-loads produces different effects on muscle fiber hypertrophy in females, but not in males.”
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 authors use tentative language ('may indicate') and correctly avoid causal claims. The claim reflects an observed outlier and hypothesis-generating insight, consistent with association-level inference.
More Accurate Statement
“One study including females reported a substantially larger effect size for type II muscle fiber hypertrophy compared to studies with only males, suggesting sex may influence the response to training load, but current evidence is insufficient to confirm this association.”
Evidence from Studies
Supporting (0)
Contradicting (1)
The Effects of Low-Load Vs. High-Load Resistance Training on Muscle Fiber Hypertrophy: A Meta-Analysis
This study looked at whether light or heavy weights build muscle better, but it didn’t check if men and women respond differently, so it can’t tell us if sex matters for muscle growth.