Both Nordic curls and stiff-leg deadlifts make your entire hamstring group bigger after 9 weeks of training—Nordic curls make them grow a bit more.
Scientific Claim
Both Nordic hamstring exercise and stiff-leg deadlift training produce significant whole hamstring hypertrophy in resistance-untrained individuals, with NHE inducing a 11.4% increase and SDL a 7.0% increase over nine weeks of training three times per week.
Original Statement
“After the resistance training programs, similar and significant whole hypertrophy was observed in both training groups (NHE: 11.4±6.5%, and SDL: 7.0±8.1%).”
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 imaging measurements allows definitive claims about muscle growth. The effect sizes are large and statistically significant.
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 magnitude of whole hamstring hypertrophy is dose-dependent and reproducible across different populations.
Whether the magnitude of whole hamstring hypertrophy is dose-dependent and reproducible across different populations.
What This Would Prove
Whether the magnitude of whole hamstring hypertrophy is dose-dependent and reproducible across different populations.
Ideal Study Design
A double-blind RCT with 120 resistance-untrained adults randomized to NHE, SDL, or control, with 3x/week training for 12 weeks, using serial MRI to measure whole hamstring volume change, controlling for nutrition and recovery.
Limitation: Cannot determine if hypertrophy is maintained after training cessation.
Prospective Cohort StudyLevel 2bWhether hypertrophy plateaus or continues beyond 9 weeks in trained individuals.
Whether hypertrophy plateaus or continues beyond 9 weeks in trained individuals.
What This Would Prove
Whether hypertrophy plateaus or continues beyond 9 weeks in trained individuals.
Ideal Study Design
A 1-year prospective cohort of 100 resistance-untrained adults performing NHE or SDL 3x/week, with monthly MRI assessments of whole hamstring volume and strength.
Limitation: Subject to adherence and attrition bias.
Evidence from Studies
Supporting (1)
The study found that doing Nordic hamstring exercises made hamstrings grow 11.4% bigger and stiff-leg deadlifts made them grow 7% bigger — just like the claim said. So yes, the study backs up what the claim claims.