If you do preacher curls with a barbell — where it’s hardest when your arm is almost straight — you’ll get stronger specifically at that position better than if you use a cable machine where it’s hardest when your arm is bent.
Scientific Claim
Barbell preacher curls produce greater gains in elbow flexion strength at 20° of elbow extension (longer muscle length) compared to cable preacher curls in young, untrained adults, with a 39% increase versus 30% (p=0.046), indicating angle-specific strength adaptation when peak torque is applied at longer muscle lengths.
Original Statement
“For elbow flexion peak torque at 20°, significant increases were observed for both CAB (pre = 30 ± 13 Nm, post = 38 ± 12 Nm; ES = 0.65; +30%) and BAR (pre = 31 ± 14 Nm, post = 42 ± 14 Nm; ES = 0.86; +39%), with greater gains for the BAR group (p = 0.046).”
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 RCT design with precise angle-specific strength testing and statistical significance (p=0.046) supports definitive causal language for this specific outcome and population.
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 training at longer muscle lengths consistently produces greater strength gains at those angles across different exercises and populations.
Whether training at longer muscle lengths consistently produces greater strength gains at those angles across different exercises and populations.
What This Would Prove
Whether training at longer muscle lengths consistently produces greater strength gains at those angles across different exercises and populations.
Ideal Study Design
A meta-analysis of all RCTs comparing exercises with peak torque at long vs. short muscle lengths (e.g., barbell vs. cable curls, deep vs. partial squats), measuring isokinetic torque at multiple joint angles, with standardized protocols and reporting of angle-specific effect sizes.
Limitation: Cannot isolate neural vs. muscular contributions to angle-specific gains.
Randomized Controlled TrialLevel 1bIn EvidenceWhether the strength advantage at 20° is due to neural adaptation, muscle growth, or both.
Whether the strength advantage at 20° is due to neural adaptation, muscle growth, or both.
What This Would Prove
Whether the strength advantage at 20° is due to neural adaptation, muscle growth, or both.
Ideal Study Design
A double-blind RCT with 60 young adults randomized to barbell or cable preacher curls, measuring torque at 20°, 60°, 100°, EMG activity, and muscle thickness pre/post 10 weeks, with control for total volume and intensity.
Limitation: Still limited to young, untrained adults; cannot confirm mechanisms without invasive measures.
Prospective Cohort StudyLevel 2bWhether the strength advantage at longer muscle lengths persists over years of training and transfers to functional tasks.
Whether the strength advantage at longer muscle lengths persists over years of training and transfers to functional tasks.
What This Would Prove
Whether the strength advantage at longer muscle lengths persists over years of training and transfers to functional tasks.
Ideal Study Design
A 5-year cohort tracking 150 resistance-trained adults who consistently use either barbell or cable preacher curls, measuring annual changes in 20° torque, functional strength (e.g., pull-up performance), and biceps morphology.
Limitation: Subject to attrition, self-selection bias, and uncontrolled lifestyle variables.
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
The study found that using a barbell for preacher curls made people stronger at a more stretched elbow position than using a cable machine, just like the claim said — and the numbers and stats match exactly.