When untrained men get stronger during dynamic leg extensions, the biggest factor is how much they can turn on their thigh muscles — bigger muscles and fiber angles help a little, but turning on the muscles harder matters most.
Scientific Claim
In previously untrained men, changes in concentric and eccentric knee extension strength after 10 weeks of heavy resistance training are most strongly associated with increases in average quadriceps muscle activation (normalized EMG), with proximal vastus lateralis or whole quadriceps cross-sectional area and vastus intermedius fascicle angle contributing as secondary predictors, explaining up to 41% of variability.
Original Statement
“The models best predicting the change in concentric and eccentric torque both included the combination of the change in quadriceps (i.e., mean of all muscles) EMG:M and the change in vastus intermedius fascicle angle combined with either a change in proximal-region VL (R² = 0.40, p < 0.001) or whole quadriceps (R² = 0.41, p < 0.001) CSA”
Evidence Quality Assessment
Claim Status
appropriately stated
Study Design Support
Design supports claim
Appropriate Language Strength
association
Can only show association/correlation
Assessment Explanation
The study design is observational and cannot prove causation. The claim correctly uses 'associated with' and reflects the regression model results without implying causality.
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.
Randomized Controlled TrialLevel 1bThat enhancing quadriceps muscle activation through neuromuscular training techniques causes greater concentric/eccentric strength gains than training focused only on hypertrophy.
That enhancing quadriceps muscle activation through neuromuscular training techniques causes greater concentric/eccentric strength gains than training focused only on hypertrophy.
What This Would Prove
That enhancing quadriceps muscle activation through neuromuscular training techniques causes greater concentric/eccentric strength gains than training focused only on hypertrophy.
Ideal Study Design
A double-blind RCT of 120 untrained men aged 18–40, randomized to either standard heavy resistance training or training augmented with biofeedback and neuromuscular electrical stimulation to maximize quadriceps activation, measuring changes in EMG:M and isokinetic torque over 10 weeks.
Limitation: Cannot determine if activation changes are due to central drive or peripheral excitability.
Longitudinal Cohort StudyLevel 2bIn EvidenceThe consistent association between increased quadriceps EMG:M and dynamic strength gains across different training volumes and intensities.
The consistent association between increased quadriceps EMG:M and dynamic strength gains across different training volumes and intensities.
What This Would Prove
The consistent association between increased quadriceps EMG:M and dynamic strength gains across different training volumes and intensities.
Ideal Study Design
A prospective cohort of 250+ untrained individuals (men and women) undergoing 10 weeks of varied resistance training protocols, with serial EMG:M, CSA, and fascicle angle measurements and weekly concentric/eccentric torque assessments.
Limitation: Cannot control for unmeasured confounders like motivation, recovery, or genetics.
Cross-Sectional StudyLevel 3Whether individuals with higher baseline quadriceps activation capacity exhibit greater potential for dynamic strength gains.
Whether individuals with higher baseline quadriceps activation capacity exhibit greater potential for dynamic strength gains.
What This Would Prove
Whether individuals with higher baseline quadriceps activation capacity exhibit greater potential for dynamic strength gains.
Ideal Study Design
A cross-sectional analysis of 300+ healthy adults aged 20–50, measuring baseline %VA and EMG:M during maximal isometric and isokinetic contractions and correlating with prior training history and strength levels.
Limitation: Cannot determine if activation capacity predicts future gains or is a result of prior training.
Evidence from Studies
Supporting (1)
This study found that when untrained men lift heavy weights for 10 weeks, their stronger knee extensions are mostly due to their muscles firing more actively, with some help from muscle size and fiber angle changes — just like the claim says.