Whether you do CrossFit or lift weights regularly, your thigh muscles end up about the same size after years of training.
Scientific Claim
Functional fitness training and strength training produce similar levels of vastus lateralis hypertrophy in experienced male practitioners, indicating that the structural adaptations in muscle size are not uniquely dependent on training modality.
Original Statement
“It was observed that the CSA did not differ between the FFT and ST groups...”
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 claim accurately reflects the non-significant difference between FFT and ST groups without implying causation or superiority, consistent with the study design.
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 FFT and ST produce equivalent muscle hypertrophy in the vastus lateralis across diverse populations.
Whether FFT and ST produce equivalent muscle hypertrophy in the vastus lateralis across diverse populations.
What This Would Prove
Whether FFT and ST produce equivalent muscle hypertrophy in the vastus lateralis across diverse populations.
Ideal Study Design
A meta-analysis of 25+ RCTs comparing FFT and ST training over 12+ weeks in healthy males aged 18–40, using ultrasound to measure vastus lateralis CSA as primary outcome, controlling for training volume and protein intake.
Limitation: Cannot resolve differences in training intensity or individual response variability.
Randomized Controlled TrialLevel 1bWhether switching from one training style to another causes equivalent hypertrophy in the vastus lateralis.
Whether switching from one training style to another causes equivalent hypertrophy in the vastus lateralis.
What This Would Prove
Whether switching from one training style to another causes equivalent hypertrophy in the vastus lateralis.
Ideal Study Design
A 16-week RCT of 60 untrained men randomized to FFT or ST, with ultrasound CSA measurements of vastus lateralis at baseline, 8, and 16 weeks, matched for total weekly volume and intensity.
Limitation: Short duration may not reflect long-term adaptations.
Prospective Cohort StudyLevel 2bWhether long-term adherence to FFT or ST leads to similar muscle growth over years.
Whether long-term adherence to FFT or ST leads to similar muscle growth over years.
What This Would Prove
Whether long-term adherence to FFT or ST leads to similar muscle growth over years.
Ideal Study Design
A 5-year prospective cohort of 100 experienced (≥2 years) FFT and ST practitioners with annual ultrasound CSA measurements of vastus lateralis, adjusting for training history, diet, and recovery.
Limitation: Cannot control for genetic predisposition or prior training history.
Evidence from Studies
Supporting (1)
Both types of training—functional fitness and traditional strength training—made the thigh muscles of experienced guys grow just as much, so it doesn’t matter which one you pick if your goal is bigger muscles.