People who do CrossFit and people who lift weights end up with about the same size leg muscles after years of training — the type of workout doesn’t seem to change muscle growth much.
Scientific Claim
Functional fitness training and strength training produce similar levels of vastus lateralis hypertrophy in experienced male practitioners, indicating that the structural muscle adaptations from these two training styles are comparable despite different exercise modalities.
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 comparison between FFT and ST groups without overstating equivalence. The language appropriately avoids causal or definitive claims.
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 and training protocols.
Whether FFT and ST produce equivalent muscle hypertrophy in the vastus lateralis across diverse populations and training protocols.
What This Would Prove
Whether FFT and ST produce equivalent muscle hypertrophy in the vastus lateralis across diverse populations and training protocols.
Ideal Study Design
A meta-analysis of 25+ studies comparing CSA changes in vastus lateralis after 12+ weeks of FFT vs ST in adults, using standardized ultrasound protocols, controlling for training volume, intensity, and protein intake.
Limitation: Cannot determine if regional hypertrophy patterns differ between modalities.
Randomized Controlled TrialLevel 1bWhether 12 weeks of FFT causes the same muscle growth as ST in untrained men.
Whether 12 weeks of FFT causes the same muscle growth as ST in untrained men.
What This Would Prove
Whether 12 weeks of FFT causes the same muscle growth as ST in untrained men.
Ideal Study Design
A 12-week double-blind RCT with 60 healthy men aged 20–30 randomized to FFT or ST, with weekly ultrasound measurements of vastus lateralis CSA at four sites, 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 vs ST leads to similar muscle growth in real-world settings.
Whether long-term adherence to FFT vs ST leads to similar muscle growth in real-world settings.
What This Would Prove
Whether long-term adherence to FFT vs ST leads to similar muscle growth in real-world settings.
Ideal Study Design
A 3-year cohort tracking 100 adult men (20–40) who self-select into FFT or ST groups, measuring vastus lateralis CSA every 6 months via ultrasound, adjusting for training frequency, diet, and recovery.
Limitation: Confounded by self-selection and adherence differences.
Evidence from Studies
Supporting (1)
The study found that people who did functional fitness and those who did traditional strength training both ended up with similarly big thigh muscles, even though they did different kinds of exercises. So yes, both types of training build muscle in the same way.