Barbell curls make you slightly stronger when your arm is almost straight, but not enough to matter much in real life — the difference is tiny.
Scientific Claim
The strength gain advantage of barbell preacher curls at 20° of elbow flexion is small (effect size = 0.23) and does not extend to other joint angles, suggesting that while torque placement can induce angle-specific adaptations, the practical significance of this difference is limited in untrained individuals.
Original Statement
“A significant advantage, albeit of small magnitude (ES = 0.23), was observed for BAR on improving extended elbow strength (at 20°) compared to CAB...”
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 study reports the effect size and explicitly labels it as small, which is accurate and appropriate. The claim reflects the data without exaggeration.
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 small strength advantages at specific joint angles from torque-emphasis training translate to meaningful functional or performance outcomes.
Whether small strength advantages at specific joint angles from torque-emphasis training translate to meaningful functional or performance outcomes.
What This Would Prove
Whether small strength advantages at specific joint angles from torque-emphasis training translate to meaningful functional or performance outcomes.
Ideal Study Design
A meta-analysis of RCTs comparing torque-emphasis training at long vs. short muscle lengths, reporting effect sizes for strength gains at specific angles and functional outcomes (e.g., lifting capacity, daily task performance) in untrained adults.
Limitation: Cannot determine if small strength differences accumulate over time or impact real-world function.
Randomized Controlled TrialLevel 1bWhether a small strength advantage at 20° translates to measurable functional benefit.
Whether a small strength advantage at 20° translates to measurable functional benefit.
What This Would Prove
Whether a small strength advantage at 20° translates to measurable functional benefit.
Ideal Study Design
A double-blind RCT of 100 untrained adults randomized to barbell or cable preacher curls, measuring not only isokinetic torque at 20° but also functional tasks (e.g., lifting from low height, carrying objects with extended arms) before and after 10 weeks of training.
Limitation: Functional tasks are subjective and may lack sensitivity.
Prospective Cohort StudyLevel 2bLong-term association between small strength differences and real-world performance.
Long-term association between small strength differences and real-world performance.
What This Would Prove
Long-term association between small strength differences and real-world performance.
Ideal Study Design
A 1-year cohort tracking 200 gym-goers using either barbell or cable preacher curls, measuring strength at 20° and self-reported performance in daily activities requiring elbow extension strength.
Limitation: Self-reported outcomes are prone to bias.
Evidence from Studies
Supporting (1)
Placing Greater Torque at Shorter or Longer Muscle Lengths? Effects of Cable vs. Barbell Preacher Curl Training on Muscular Strength and Hypertrophy in Young Adults