If you use the same weight and do the same number of reps, it doesn't matter if you curl with your arm in front or behind you — what matters is just doing it consistently and getting stronger over time.
Scientific Claim
When resistance profiles are matched, training the elbow flexors with the shoulder flexed or extended produces similar increases in muscle thickness and strength, suggesting that exercise selection for hypertrophy and strength should prioritize consistency and load progression over joint angle manipulation.
Original Statement
“In conclusion, the shoulder joint angle does not seem to affect muscle hypertrophy and maximum strength gains after different elbow flexion exercises matched for resistance profiles.”
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 design isolates shoulder angle as the variable while controlling resistance profiles, allowing definitive conclusions about its irrelevance under these conditions.
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 matching resistance profiles eliminates differences in hypertrophy and strength outcomes across all elbow flexion exercises with varying joint angles.
Whether matching resistance profiles eliminates differences in hypertrophy and strength outcomes across all elbow flexion exercises with varying joint angles.
What This Would Prove
Whether matching resistance profiles eliminates differences in hypertrophy and strength outcomes across all elbow flexion exercises with varying joint angles.
Ideal Study Design
A systematic review and meta-analysis of all RCTs comparing elbow flexion exercises (e.g., Preacher, incline, dumbbell, barbell) with matched resistance profiles, measuring regional muscle thickness and 1RM strength, across populations and durations ≥8 weeks.
Limitation: Cannot determine if unmatched profiles (e.g., barbell vs. cable) produce different outcomes.
Randomized Controlled TrialLevel 1bWhether training volume and load progression are more predictive of hypertrophy and strength than exercise variation.
Whether training volume and load progression are more predictive of hypertrophy and strength than exercise variation.
What This Would Prove
Whether training volume and load progression are more predictive of hypertrophy and strength than exercise variation.
Ideal Study Design
A 16-week RCT of 60 young men randomized to three groups: 1) variable exercises with matched volume, 2) fixed exercise with matched volume, 3) variable exercises with unmatched volume; measuring muscle thickness and 1RM as primary outcomes.
Limitation: Does not test psychological adherence or long-term adherence effects.
Prospective Cohort StudyLevel 2bWhether individuals who prioritize load progression over exercise variation achieve superior long-term hypertrophy and strength.
Whether individuals who prioritize load progression over exercise variation achieve superior long-term hypertrophy and strength.
What This Would Prove
Whether individuals who prioritize load progression over exercise variation achieve superior long-term hypertrophy and strength.
Ideal Study Design
A 5-year prospective cohort of 200 resistance-trained individuals tracking exercise variation, load progression, volume, and muscle strength/hypertrophy outcomes, with annual ultrasound and 1RM testing.
Limitation: Cannot control for self-selection bias or nutrition differences.
Randomized Controlled TrialLevel 1bWhether psychological adherence and satisfaction differ between fixed vs. varied elbow flexion exercises, influencing long-term outcomes.
Whether psychological adherence and satisfaction differ between fixed vs. varied elbow flexion exercises, influencing long-term outcomes.
What This Would Prove
Whether psychological adherence and satisfaction differ between fixed vs. varied elbow flexion exercises, influencing long-term outcomes.
Ideal Study Design
A 12-week RCT of 40 participants randomized to fixed (only Preacher) vs. varied (rotating Preacher, incline, dumbbell) elbow flexion protocols, measuring adherence, satisfaction, muscle thickness, and strength, with qualitative interviews on motivation.
Limitation: Does not test physiological superiority, only behavioral factors.
Cross-Sectional StudyLevel 3bWhether elite athletes who use fewer exercise variations achieve greater hypertrophy and strength than those who rotate exercises frequently.
Whether elite athletes who use fewer exercise variations achieve greater hypertrophy and strength than those who rotate exercises frequently.
What This Would Prove
Whether elite athletes who use fewer exercise variations achieve greater hypertrophy and strength than those who rotate exercises frequently.
Ideal Study Design
A cross-sectional analysis of 100 elite bodybuilders and powerlifters, categorizing them by exercise variation frequency (low: ≤2 variations, high: ≥5 variations), measuring muscle thickness via ultrasound and 1RM strength, controlling for training age and volume.
Limitation: Cannot determine causation; confounded by experience and genetics.
Evidence from Studies
Supporting (1)
When you do bicep curls with your arm up or down, but use the same amount of weight and effort, your arms get just as strong and big either way — so it doesn’t matter which position you pick, just keep doing it consistently and getting stronger.