Doing bicep curls only halfway up might help you push harder when your arm is bent at 100 degrees, even though you didn’t train that angle—possibly because your muscle got a bit bigger in the stretched part.
Scientific Claim
In resistance-trained individuals, partial range of motion training at long muscle lengths (0°–70°) may be associated with a modestly greater improvement in maximal voluntary contraction (MVC) at 100° of elbow flexion compared to full range of motion training (0°–140°), with a small effect size (SMD = 0.24) and moderate Bayesian evidence (BF = 3.02), potentially due to enhanced distal muscle hypertrophy or prolonged tension in mid-range positions.
Original Statement
“MVC at 100° (SMD = 0.24 and Bayes factor = 3.02) demonstrated greater but negligible improvements with fROM, with weak to moderate evidence supporting the hypothesis of differential effectiveness across interventions.”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
probability
Can suggest probability/likelihood
Assessment Explanation
The moderate Bayes factor (BF=3.02) and small SMD (0.24) support probabilistic language. The claim avoids causation and correctly frames the finding as a potential association linked to hypertrophy.
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 pROMinitial consistently improves strength at mid-range joint angles (e.g., 80°–110°) more than fROM across multiple RCTs in trained populations.
Whether pROMinitial consistently improves strength at mid-range joint angles (e.g., 80°–110°) more than fROM across multiple RCTs in trained populations.
What This Would Prove
Whether pROMinitial consistently improves strength at mid-range joint angles (e.g., 80°–110°) more than fROM across multiple RCTs in trained populations.
Ideal Study Design
A meta-analysis of RCTs comparing pROMinitial vs. fROM in resistance-trained adults, measuring MVC at multiple joint angles (40°, 80°, 100°, 120°), with standardized protocols, controlling for training volume and duration.
Limitation: Cannot determine if strength gains are due to hypertrophy or neural adaptations.
Randomized Controlled TrialLevel 1bIn EvidenceWhether pROMinitial causes greater MVC gains at 100° than fROM in trained individuals.
Whether pROMinitial causes greater MVC gains at 100° than fROM in trained individuals.
What This Would Prove
Whether pROMinitial causes greater MVC gains at 100° than fROM in trained individuals.
Ideal Study Design
A double-blind, randomized, crossover RCT with 50+ resistance-trained adults, performing 12 weeks of unilateral preacher curls (pROMinitial vs. fROM), measuring MVC at 40°, 80°, 100°, and 120° pre/post, with ultrasound for muscle thickness and EMG for neural activation.
Limitation: Cannot prove mechanism (hypertrophy vs. neural) without biopsy or imaging.
Prospective Cohort StudyLevel 2bWhether lifters who use pROMinitial show greater strength gains at mid-range angles over time compared to fROM users.
Whether lifters who use pROMinitial show greater strength gains at mid-range angles over time compared to fROM users.
What This Would Prove
Whether lifters who use pROMinitial show greater strength gains at mid-range angles over time compared to fROM users.
Ideal Study Design
A 1-year prospective cohort of 200+ trained lifters self-selecting pROMinitial or fROM training, with quarterly MVC testing at 100° and ultrasound for muscle thickness, controlling for training logs and diet.
Limitation: Confounded by self-selection and uncontrolled variables.
Animal Model StudyLevel 4Whether training at long muscle lengths increases motor unit recruitment at mid-range joint angles via muscle growth.
Whether training at long muscle lengths increases motor unit recruitment at mid-range joint angles via muscle growth.
What This Would Prove
Whether training at long muscle lengths increases motor unit recruitment at mid-range joint angles via muscle growth.
Ideal Study Design
A rat study with 40 animals, trained for 8 weeks with either pROMinitial or fROM elbow flexion, measuring MVC at multiple angles, muscle fiber CSA, and motor unit recruitment thresholds via EMG.
Limitation: Cannot replicate human voluntary effort or motor learning.
Case-Control StudyLevel 3Whether athletes using pROMinitial have greater MVC at 100° than those using fROM, after matching for training history.
Whether athletes using pROMinitial have greater MVC at 100° than those using fROM, after matching for training history.
What This Would Prove
Whether athletes using pROMinitial have greater MVC at 100° than those using fROM, after matching for training history.
Ideal Study Design
A case-control study comparing MVC at 100° in 30 elite athletes using pROMinitial vs. 30 matched controls using fROM, with ultrasound for muscle thickness and training logs.
Limitation: Retrospective and subject to selection bias.
Evidence from Studies
Supporting (0)
Contradicting (1)
The study found that lifting all the way (full range) made people stronger at 100° elbow bend better than lifting only halfway (partial range), even though the claim said the opposite.