If you do the same amount of work with your arm in front or behind you, you'll get just as strong at lifting heavy weights — the position doesn't matter.
Scientific Claim
Maximum strength gains in elbow flexion exercises are equivalent (28–37% improvement) after 10 weeks of training with the shoulder flexed or extended, provided resistance profiles are matched, indicating that strength adaptation is not dependent on muscle length during training.
Original Statement
“Significant improvements in maximum strength were observed (p < 0.05), with equivalent results between conditions (PREA: 28% [ES: 0.85], BAYE: 37% [ES: 1.22]; equivalence testing, p-values = 0.061, 0.637).”
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 use of equivalence testing (TOST) with predefined bounds and statistical non-inferiority confirms the claim with high confidence within the study's scope.
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 strength gains in elbow flexion are equivalent across shoulder positions in diverse populations and training durations.
Whether strength gains in elbow flexion are equivalent across shoulder positions in diverse populations and training durations.
What This Would Prove
Whether strength gains in elbow flexion are equivalent across shoulder positions in diverse populations and training durations.
Ideal Study Design
A systematic review and meta-analysis of all RCTs comparing shoulder flexed vs. extended elbow flexion exercises, measuring 1RM strength in the trained exercise, with standardized volume, intensity, and resistance profiles, across populations aged 18–40, training ≥8 weeks.
Limitation: Cannot assess transfer to non-specific strength tests or functional performance.
Randomized Controlled TrialLevel 1bWhether strength gains transfer to non-specific elbow flexion tests (e.g., dumbbell curls) when training with different shoulder positions.
Whether strength gains transfer to non-specific elbow flexion tests (e.g., dumbbell curls) when training with different shoulder positions.
What This Would Prove
Whether strength gains transfer to non-specific elbow flexion tests (e.g., dumbbell curls) when training with different shoulder positions.
Ideal Study Design
A 12-week RCT of 50 young men randomized to shoulder-flexed or extended cable curls, measuring 1RM in the trained exercise and 1RM in untrained dumbbell curls, with pre/post EMG and torque-angle profiles to assess neural adaptations.
Limitation: Does not test long-term retention or transfer to dynamic sports tasks.
Prospective Cohort StudyLevel 2bWhether long-term training with one shoulder position leads to superior strength retention or performance in real-world tasks.
Whether long-term training with one shoulder position leads to superior strength retention or performance in real-world tasks.
What This Would Prove
Whether long-term training with one shoulder position leads to superior strength retention or performance in real-world tasks.
Ideal Study Design
A 3-year prospective cohort of 100 resistance-trained individuals who consistently use either Preacher or incline curls, measuring annual 1RM in both exercises and functional strength tests (e.g., pull-ups, rows), controlling for total volume and diet.
Limitation: Cannot control for technique drift or training history confounders.
Animal Model StudyLevel 5Whether neural adaptations (e.g., motor unit recruitment) differ between shoulder positions during elbow flexion.
Whether neural adaptations (e.g., motor unit recruitment) differ between shoulder positions during elbow flexion.
What This Would Prove
Whether neural adaptations (e.g., motor unit recruitment) differ between shoulder positions during elbow flexion.
Ideal Study Design
A study in rats with implanted EMG and force transducers during electrically induced elbow flexion at shoulder flexed vs. extended positions, measuring motor unit recruitment patterns and spinal reflex excitability over 8 weeks.
Limitation: Cannot replicate human voluntary effort or cognitive factors in strength.
Cross-Sectional StudyLevel 3bWhether experienced lifters who specialize in one shoulder position show superior strength in that specific movement.
Whether experienced lifters who specialize in one shoulder position show superior strength in that specific movement.
What This Would Prove
Whether experienced lifters who specialize in one shoulder position show superior strength in that specific movement.
Ideal Study Design
A cross-sectional analysis of 50 experienced lifters who primarily use either Preacher or incline curls, measuring 1RM in both exercises and comparing strength ratios, controlling for training age and total volume.
Limitation: Cannot determine if differences are due to training or selection bias.
Evidence from Studies
Supporting (1)
This study found that whether you do bicep curls with your arm stretched out behind you or bent in front of you, you get about the same strength gains after 10 weeks — as long as the resistance feels the same. So, muscle length during the exercise doesn’t matter for building strength.