Doing a full squat or starting a bicep curl from the bottom makes your muscles grow more at the far ends (like the top of your thigh or the outer part of your bicep) than doing partial reps from the top.
Scientific Claim
Training with full or initial range of motion (ROM) is associated with greater hypertrophy in distal muscle regions compared to final ROM, likely because these ROMs better engage muscles at longer lengths with higher external torque.
Original Statement
“Full ROM induced greater increases in the rectus femoris at 60% and 70% of the thigh length... Initial ROM induced greater increases in the rectus femoris at 40%, 50%, and 70% of the thigh length... greater hypertrophy often observed after exercises and ROMs that train muscles at longer lengths.”
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 study uses causal language ('induced greater increases') but is a narrative review. The evidence shows association between ROM position and regional hypertrophy, not causation.
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 1bWhether initial ROM training causes greater distal hypertrophy than final ROM when torque and volume are matched.
Whether initial ROM training causes greater distal hypertrophy than final ROM when torque and volume are matched.
What This Would Prove
Whether initial ROM training causes greater distal hypertrophy than final ROM when torque and volume are matched.
Ideal Study Design
A double-blind RCT of 50 untrained adults assigned to 12 weeks of knee extension: Group A trains from 100° to 65° (initial ROM, long length); Group B trains from 65° to 30° (final ROM, short length); both use identical load, volume, and tempo. Measure vastus lateralis thickness at 40%, 50%, 60%, 70% of thigh length via ultrasound.
Limitation: Cannot control for individual biomechanical differences in torque-angle curves.
Systematic Review & Meta-AnalysisLevel 1aWhether initial/full ROM consistently produces greater distal hypertrophy than final ROM across multiple muscles and populations.
Whether initial/full ROM consistently produces greater distal hypertrophy than final ROM across multiple muscles and populations.
What This Would Prove
Whether initial/full ROM consistently produces greater distal hypertrophy than final ROM across multiple muscles and populations.
Ideal Study Design
A meta-analysis of all RCTs comparing initial/full ROM vs. final ROM training in quadriceps, hamstrings, and triceps, measuring regional muscle thickness at proximal, middle, and distal sites, with ≥20 studies and ≥500 participants total.
Limitation: Cannot determine if torque differences or muscle length are the true drivers.
Prospective Cohort StudyLevel 2bWhether habitual use of full ROM predicts greater distal muscle growth over time.
Whether habitual use of full ROM predicts greater distal muscle growth over time.
What This Would Prove
Whether habitual use of full ROM predicts greater distal muscle growth over time.
Ideal Study Design
A 3-year cohort of 120 resistance-trained athletes tracking their preferred ROMs in squats, deadlifts, and curls, with annual MRI scans of quadriceps and biceps to measure regional hypertrophy, controlling for training volume and intensity.
Limitation: Cannot control for genetic variation in muscle fiber distribution.
Evidence from Studies
Supporting (1)
This study says that lifting weights through a full or starting range of motion makes muscles grow better because it stretches them more while still pushing hard—exactly what the claim says.