Whether you do full or half curls, your arms still get stronger and a bit bigger—so you don’t need to do one over the other to see results.
Scientific Claim
In resistance-trained individuals, both partial range of motion training at long muscle lengths (0°–70°) and full range of motion training (0°–140°) produce significant overall improvements in elbow flexor muscle thickness and strength, indicating that either protocol can effectively maintain or enhance muscular adaptations in trained populations.
Original Statement
“These findings suggest that pROMinitial may offer modest benefits for regional hypertrophy, particularly at longer muscle lengths. The results indicate that both training modalities can induce beneficial adaptations, with pROMinitial offering slight advantages in specific contexts.”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
probability
Can suggest probability/likelihood
Assessment Explanation
The claim uses 'can induce beneficial adaptations'—a probabilistic verb appropriate for the study design. It reflects the strong within-group improvements (BF>30) and avoids overstatement of superiority.
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 both pROMinitial and fROM consistently produce significant hypertrophy and strength gains in resistance-trained individuals across multiple RCTs.
Whether both pROMinitial and fROM consistently produce significant hypertrophy and strength gains in resistance-trained individuals across multiple RCTs.
What This Would Prove
Whether both pROMinitial and fROM consistently produce significant hypertrophy and strength gains in resistance-trained individuals across multiple RCTs.
Ideal Study Design
A meta-analysis of all RCTs comparing pROMinitial and fROM in resistance-trained adults (≥2 years experience), measuring muscle thickness and 1RM as primary outcomes, with at least 6 weeks of training and standardized protocols.
Limitation: Cannot determine which is superior in specific contexts.
Randomized Controlled TrialLevel 1bIn EvidenceWhether both pROMinitial and fROM independently induce significant hypertrophy and strength gains in trained individuals.
Whether both pROMinitial and fROM independently induce significant hypertrophy and strength gains in trained individuals.
What This Would Prove
Whether both pROMinitial and fROM independently induce significant hypertrophy and strength gains in trained individuals.
Ideal Study Design
A double-blind, randomized, crossover RCT with 50+ resistance-trained adults, performing 12 weeks of unilateral preacher curls (pROMinitial and fROM), with pre/post measurements of muscle thickness (ultrasound) and 1RM, showing significant within-group improvements.
Limitation: Still limited to one exercise and muscle group.
Prospective Cohort StudyLevel 2bWhether resistance-trained individuals maintain or improve muscle and strength over time using either pROMinitial or fROM in real-world settings.
Whether resistance-trained individuals maintain or improve muscle and strength over time using either pROMinitial or fROM in real-world settings.
What This Would Prove
Whether resistance-trained individuals maintain or improve muscle and strength over time using either pROMinitial or fROM in real-world settings.
Ideal Study Design
A 1-year prospective cohort of 200+ resistance-trained lifters using either pROMinitial or fROM as their primary elbow flexor training method, with quarterly measurements of muscle thickness and 1RM.
Limitation: Cannot control for confounding variables like nutrition or recovery.
Case-Control StudyLevel 3Whether trained individuals using either pROMinitial or fROM have higher muscle thickness and strength than untrained controls.
Whether trained individuals using either pROMinitial or fROM have higher muscle thickness and strength than untrained controls.
What This Would Prove
Whether trained individuals using either pROMinitial or fROM have higher muscle thickness and strength than untrained controls.
Ideal Study Design
A case-control study comparing 50+ resistance-trained lifters using pROMinitial or fROM with 50+ untrained controls, measuring muscle thickness and 1RM, matched for age and sex.
Limitation: Cannot establish causation or isolate training effects.
Cross-Sectional StudyLevel 3Whether resistance-trained individuals using either pROMinitial or fROM have greater muscle thickness and strength than sedentary individuals.
Whether resistance-trained individuals using either pROMinitial or fROM have greater muscle thickness and strength than sedentary individuals.
What This Would Prove
Whether resistance-trained individuals using either pROMinitial or fROM have greater muscle thickness and strength than sedentary individuals.
Ideal Study Design
A cross-sectional study comparing muscle thickness and 1RM in 100+ resistance-trained lifters (using either ROM) vs. 100+ sedentary controls, matched for age and sex.
Limitation: Cannot determine if training caused the differences.
Evidence from Studies
Supporting (1)
Both ways of doing bicep curls — bending the arm only partway and bending it all the way — made people’s biceps stronger and bigger, with almost no difference between them. So either method works fine.