Your muscles grow bigger mainly because of how much total force they feel over time—not whether you do your workouts all at once or spread out over the week.
Evidence from Studies
Supporting (4)
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Effect of different training frequencies on maximal strength performance and muscle hypertrophy in trained individuals—a within-subject design
Even if you lift weights once a week or three times a week, as long as you do the same total amount of work, your muscles grow the same. This supports the idea that it’s the total effort over time, not how you spread it out, that matters most.
Equalization of Training Protocols by Time Under Tension Determines the Magnitude of Changes in Strength and Muscular Hypertrophy
The study showed that whether you lift light weights many times or heavy weights fewer times, as long as the total time your muscles are under tension is the same, you get the same muscle growth. This supports the idea that total tension matters more than how you spread it out.
Load-induced human skeletal muscle hypertrophy: Mechanisms, myths, and misconceptions
This study says lifting weights makes muscles grow mainly because of the physical tension they create, not because of sweat, pump, or hormones — and it doesn’t matter if you lift a little every day or a lot once a week, as long as the total tension adds up.
This study says it’s not just how heavy you lift, but how long your muscles are working during each rep that makes them grow—so even if you spread out your workouts, what matters most is the total time your muscles are under tension.
Contradicting (2)
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A Comparison Between Synergist and Nonsynergist Resistance Training Schemes in Recreationally Trained Men.
Both training styles made people’s muscles grow the same amount, as long as they lifted the same total weight—so how you spread out your workouts doesn’t seem to matter as much as how much weight you lift overall.
The study says muscle growth might be more about burning out your muscles with intense reps (metabolic stress) than just lifting heavy weights over time (mechanical tension), which goes against the claim that only mechanical tension matters.
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.