People who have been doing serious workouts like CrossFit or weightlifting for years have bigger leg muscles than people who just stay active without formal training.
Scientific Claim
Men with at least two years of experience in functional fitness training or strength training exhibit greater vastus lateralis muscle cross-sectional area than physically active controls without structured resistance training, suggesting that both training modalities promote lower limb muscle hypertrophy compared to general physical activity.
Original Statement
“It was observed that the CSA did not differ between the FFT and ST groups, and showed higher values in relation to the control group.”
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 cross-sectional design cannot prove causation, but the claim correctly uses association to describe the observed difference in muscle size between trained and untrained groups.
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 functional fitness and strength training produce equivalent or differential muscle hypertrophy in the vastus lateralis across diverse populations over time.
Whether functional fitness and strength training produce equivalent or differential muscle hypertrophy in the vastus lateralis across diverse populations over time.
What This Would Prove
Whether functional fitness and strength training produce equivalent or differential muscle hypertrophy in the vastus lateralis across diverse populations over time.
Ideal Study Design
A meta-analysis of 20+ randomized controlled trials comparing 12+ months of FFT (e.g., CrossFit-style) vs. ST (e.g., linear periodization) in healthy adult males aged 20–40, with CSA measured via ultrasound at baseline and endpoint, controlling for volume, intensity, and protein intake.
Limitation: Cannot establish causation in individual studies, only summarizes existing associations.
Randomized Controlled TrialLevel 1bWhether switching from general activity to FFT or ST causes measurable hypertrophy in the vastus lateralis over time.
Whether switching from general activity to FFT or ST causes measurable hypertrophy in the vastus lateralis over time.
What This Would Prove
Whether switching from general activity to FFT or ST causes measurable hypertrophy in the vastus lateralis over time.
Ideal Study Design
A 12-month double-blind RCT of 100 sedentary men aged 20–35 randomized to FFT (3x/week, HIIT + resistance) or ST (3x/week, isolated lifts) with ultrasound CSA measurements of vastus lateralis at 0, 6, and 12 months, controlling for diet and activity logs.
Limitation: Cannot account for long-term adherence or real-world variability in training execution.
Prospective Cohort StudyLevel 2bWhether long-term adherence to FFT or ST predicts progressive muscle growth in the vastus lateralis over years.
Whether long-term adherence to FFT or ST predicts progressive muscle growth in the vastus lateralis over years.
What This Would Prove
Whether long-term adherence to FFT or ST predicts progressive muscle growth in the vastus lateralis over years.
Ideal Study Design
A 5-year prospective cohort tracking 200 adult males starting either FFT or ST, with annual ultrasound CSA measurements of vastus lateralis, adjusting for age, diet, sleep, and training volume.
Limitation: Subject to attrition bias and self-reporting errors in training logs.
Evidence from Studies
Supporting (1)
People who did either functional fitness or weight training for at least two years had bigger leg muscles than people who were just generally active but didn’t do structured workouts — so yes, those kinds of training build muscle better than just being active.