Nordic curls make one part of your hamstring (semitendinosus) grow more, while stiff-leg deadlifts make another part (semimembranosus) grow more—so different exercises target different muscles in the same group.
Scientific Claim
Nordic hamstring exercise induces greater selective hypertrophy of the semitendinosus muscle (24.3% increase) compared to stiff-leg deadlift, which induces greater selective hypertrophy of the semimembranosus (11.2% increase), indicating that exercise selection can target specific hamstring muscles differently.
Original Statement
“The NHE group and SDL group, however, presented a selective hypertrophy of ST (24.3±10.8%) and SM (11.2±12.7%), respectively.”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
definitive
Can make definitive causal claims
Assessment Explanation
The RCT design with direct muscle volume measurements allows definitive claims about differential hypertrophy patterns. The reported effect sizes are large and consistent with biomechanical expectations.
Gold Standard Evidence Needed
According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.
Randomized Controlled TrialLevel 1bIn EvidenceWhether the selective hypertrophy patterns are reproducible and dose-dependent across different populations and training volumes.
Whether the selective hypertrophy patterns are reproducible and dose-dependent across different populations and training volumes.
What This Would Prove
Whether the selective hypertrophy patterns are reproducible and dose-dependent across different populations and training volumes.
Ideal Study Design
A double-blind RCT with 120 resistance-untrained adults randomized to NHE, SDL, or combined training, with 3x/week sessions for 12 weeks, using serial MRI to track SM and ST volume changes, controlling for load progression and recovery.
Limitation: Cannot determine neural contributions to strength gains.
Prospective Cohort StudyLevel 2bWhether selective hypertrophy patterns persist in trained athletes over years of training.
Whether selective hypertrophy patterns persist in trained athletes over years of training.
What This Would Prove
Whether selective hypertrophy patterns persist in trained athletes over years of training.
Ideal Study Design
A 3-year prospective cohort of 150 athletes (soccer, sprinters) performing either NHE or SDL as their primary hamstring exercise, with annual MRI assessments of SM and ST volume and strength testing.
Limitation: Subject to attrition and confounding from other training variables.
Cross-Sectional StudyLevel 3Whether habitual NHE or SDL users show consistent selective hypertrophy patterns in real-world settings.
Whether habitual NHE or SDL users show consistent selective hypertrophy patterns in real-world settings.
What This Would Prove
Whether habitual NHE or SDL users show consistent selective hypertrophy patterns in real-world settings.
Ideal Study Design
A cross-sectional analysis of 200 athletes with ≥2 years of consistent NHE or SDL training, comparing SM and ST volumes via MRI, controlling for total training volume and sport type.
Limitation: Cannot establish causality or direction of effect.
Evidence from Studies
Supporting (1)
The study found that doing Nordic hamstring curls makes one hamstring muscle (semitendinosus) grow more, while stiff-leg deadlifts make another hamstring muscle (semimembranosus) grow more — just like the claim says.