If you only do the first half of a leg extension, your upper thigh muscle grows more than if you do the full motion.
Scientific Claim
Partial range of motion performed in the initial part of the movement is associated with greater proximal rectus femoris hypertrophy than full range of motion, with between-group effect sizes of 0.35–0.38.
Original Statement
“Initial pROM produced more favorable proximal rectus femoris hypertrophy than fROM (between-groups ES: 0.35–0.38).”
Evidence Quality Assessment
Claim Status
overstated
Study Design Support
Design cannot support claim
Appropriate Language Strength
association
Can only show association/correlation
Assessment Explanation
The abstract implies causation ('produced more favorable'), but the design of included studies is unknown. Only an associative interpretation is valid.
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 1aIn EvidenceWhether initial partial ROM consistently enhances proximal quad hypertrophy compared to full ROM across studies.
Whether initial partial ROM consistently enhances proximal quad hypertrophy compared to full ROM across studies.
What This Would Prove
Whether initial partial ROM consistently enhances proximal quad hypertrophy compared to full ROM across studies.
Ideal Study Design
A systematic review and meta-analysis of 12+ RCTs comparing initial partial ROM (0–45°) vs. full ROM (0–120°) in knee extension exercises, measuring proximal rectus femoris thickness via ultrasound in healthy adults at 8–12 weeks, with matched volume and intensity.
Limitation: Cannot determine if results are due to muscle length or tension profile.
Randomized Controlled TrialLevel 1bCausal effect of initial partial ROM on proximal rectus femoris growth.
Causal effect of initial partial ROM on proximal rectus femoris growth.
What This Would Prove
Causal effect of initial partial ROM on proximal rectus femoris growth.
Ideal Study Design
A double-blind RCT of 50 adults performing 10 weeks of knee extensions, randomized to initial partial ROM (0–45°) or full ROM (0–120°), with muscle thickness measured via ultrasound at baseline, 6, and 10 weeks, controlling for training history.
Limitation: Short duration limits long-term applicability.
Prospective Cohort StudyLevel 2bAssociation between habitual initial partial ROM use and proximal quad development in trained individuals.
Association between habitual initial partial ROM use and proximal quad development in trained individuals.
What This Would Prove
Association between habitual initial partial ROM use and proximal quad development in trained individuals.
Ideal Study Design
A 1-year cohort of 100 resistance-trained athletes tracking their knee extension ROM preference, with ultrasound measurements of proximal rectus femoris at 6 and 12 months, adjusting for training volume and frequency.
Limitation: Cannot control for unmeasured confounders like recovery or nutrition.
Evidence from Studies
Supporting (1)
Which ROMs Lead to Rome? A Systematic Review of the Effects of Range of Motion on Muscle Hypertrophy
The study found that doing part of a leg exercise at the start (not all the way down) made the front thigh muscle grow more than doing the full movement — and the numbers match exactly what the claim says.