Even when your hamstrings get bigger from training, that doesn’t really predict how much stronger you’ll get at the other exercise—so bigger muscles don’t mean much more strength in this case.
Scientific Claim
Changes in whole hamstring muscle volume are not strongly correlated with strength transfer between Nordic hamstring exercise and stiff-leg deadlift in resistance-untrained individuals, with correlations below r=0.3 for all muscles except biceps femoris in the SDL group.
Original Statement
“Finally, non-significant correlations were found between strength transfer and both whole and selective hamstring hypertrophy (r≤0.3), except for the BF in SDL (r=0.6).”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
probability
Can suggest probability/likelihood
Assessment Explanation
Correlations are inherently probabilistic; the authors correctly report non-significant r-values and avoid causal language. The r=0.6 for BF in SDL is noted as an outlier, not overgeneralized.
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.
Systematic Review & Meta-AnalysisLevel 1aWhether the weak correlation between hypertrophy and strength transfer is consistent across multiple studies and exercise pairs.
Whether the weak correlation between hypertrophy and strength transfer is consistent across multiple studies and exercise pairs.
What This Would Prove
Whether the weak correlation between hypertrophy and strength transfer is consistent across multiple studies and exercise pairs.
Ideal Study Design
A meta-analysis of 20+ RCTs measuring hamstring hypertrophy and cross-transfer strength gains across different exercise pairs (e.g., NHE-SDL, leg curl-hip thrust), using standardized MRI and 1RM protocols, with subgroup analysis by training status.
Limitation: Cannot control for measurement variability across studies.
Randomized Controlled TrialLevel 1bWhether manipulating hypertrophy independently (e.g., via pharmacological means) affects strength transfer.
Whether manipulating hypertrophy independently (e.g., via pharmacological means) affects strength transfer.
What This Would Prove
Whether manipulating hypertrophy independently (e.g., via pharmacological means) affects strength transfer.
Ideal Study Design
A double-blind RCT with 80 participants randomized to NHE + anabolic agent (e.g., testosterone) vs. NHE + placebo, measuring hypertrophy and SDL 1RM transfer over 12 weeks, to isolate hypertrophy’s causal role.
Limitation: Ethical and practical limitations of pharmacological manipulation in healthy populations.
Prospective Cohort StudyLevel 2bWhether individuals with high vs. low hypertrophy responses show different strength transfer outcomes over time.
Whether individuals with high vs. low hypertrophy responses show different strength transfer outcomes over time.
What This Would Prove
Whether individuals with high vs. low hypertrophy responses show different strength transfer outcomes over time.
Ideal Study Design
A 6-month prospective cohort of 100 resistance-untrained adults undergoing identical NHE/SDL training, with weekly MRI and strength testing, stratifying participants into high/low hypertrophy responders and comparing transfer outcomes.
Limitation: Cannot control for adherence or lifestyle confounders.
Evidence from Studies
Supporting (1)
The study found that getting stronger at one hamstring exercise doesn’t really come from muscles getting bigger — except maybe in one case — which is exactly what the claim says.