The Claim

In resistance-trained men, an 8-week resistance training program performed 4 times per week results in significant increases in vastus lateralis and rectus femoris muscle thickness (mean increases of 0.12–0.18 cm), with no statistically significant differences between fixed-exercise and randomly varied exercise protocols (p > 0.05, effect size < 0.2).

Source: The effects of exercise variation in muscle thickness, maximal strength and motivation in resistance trained men

What the research says

Supports is higher

Support is ahead, but a single strong opposing study can change this.

Supports
54score
Challenges
0score

These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.

Quantitative
1 study reviewed
In plain English

If you're a guy who's already lifting weights, doing 4 workouts a week for 8 weeks will noticeably grow your thigh muscles — and it doesn’t matter whether you stick to the same routine or mix it up every time.

See the scientific wording

In resistance-trained men, an 8-week resistance training program 4 times per week produces large increases in vastus lateralis and rectus femoris muscle thickness (mean increases of 0.12–0.18 cm), regardless of whether exercises are fixed or randomly varied, with no statistically significant between-group differences (p > 0.05, ES < 0.2).

What the research says

1 study
  1. Study: The effects of exercise variation in muscle thickness, maximal strength and motivation in resistance trained men

    The study looked at whether switching up exercises or keeping them the same led to more leg muscle growth in trained men. Both methods worked equally well, which supports the claim.

Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies

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