Whether you do preacher curls with a cable machine (harder when your arm is bent) or a barbell (harder when your arm is straight), your biceps grow about the same amount after 10 weeks of training.
Scientific Claim
Ten weeks of preacher curl training using either a cable-pulley system (emphasizing torque at short muscle lengths) or a barbell (emphasizing torque at long muscle lengths) produces similar increases in biceps brachii thickness (7–8%) in young, untrained adults, indicating that muscle hypertrophy is not significantly influenced by whether resistance is highest during elbow flexion or extension.
Original Statement
“For biceps brachii thickness, significant increases were observed for both CAB (pre = 25 ± 5 mm, post = 27 ± 6 mm; ES = 0.37; +7%) and BAR (pre = 24 ± 4 mm, post = 26 ± 4 mm; ES = 0.35; +8%), without significant difference between them (p = 0.346).”
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 is a randomized controlled trial with direct measurement of muscle thickness, allowing causal inference. The conclusion matches the data and does not overgeneralize beyond the studied population or exercise.
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 torque emphasis at long vs. short muscle lengths consistently produces equivalent hypertrophy across multiple RCTs using different exercises and populations.
Whether torque emphasis at long vs. short muscle lengths consistently produces equivalent hypertrophy across multiple RCTs using different exercises and populations.
What This Would Prove
Whether torque emphasis at long vs. short muscle lengths consistently produces equivalent hypertrophy across multiple RCTs using different exercises and populations.
Ideal Study Design
A meta-analysis of all RCTs comparing resistance training with torque emphasis at long vs. short muscle lengths in healthy adults, using ultrasound or MRI to measure muscle thickness in elbow flexors, with standardized training protocols (3x/week, 8–12 RM, 10+ weeks), including at least 5 studies with n≥20 per group.
Limitation: Cannot establish causation in individual studies, only summarizes existing evidence.
Randomized Controlled TrialLevel 1bIn EvidenceCausal effect of torque placement on hypertrophy in biceps brachii under controlled conditions.
Causal effect of torque placement on hypertrophy in biceps brachii under controlled conditions.
What This Would Prove
Causal effect of torque placement on hypertrophy in biceps brachii under controlled conditions.
Ideal Study Design
A double-blind, randomized trial of 60 healthy adults aged 18–30, assigned to 12 weeks of preacher curls with either cable (peak torque at 100°) or barbell (peak torque at 20°), 3x/week, 3 sets to failure, with biceps thickness measured via MRI at baseline, 6, and 12 weeks, controlling for diet and activity.
Limitation: Limited to specific exercise and population; cannot generalize to other muscles or training styles.
Prospective Cohort StudyLevel 2bLong-term association between torque emphasis pattern and hypertrophy in real-world training environments.
Long-term association between torque emphasis pattern and hypertrophy in real-world training environments.
What This Would Prove
Long-term association between torque emphasis pattern and hypertrophy in real-world training environments.
Ideal Study Design
A 1-year prospective cohort tracking 200 untrained adults who self-select either cable or barbell preacher curls as their primary biceps exercise, measuring biceps thickness via ultrasound every 3 months while controlling for total volume and intensity.
Limitation: Cannot control for confounding variables like diet, recovery, or adherence.
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