Check out this study by Gomes et al. (2018) which found greater strength development and muscle growth when training each muscle 6 times per week compared to 3 times per week! Although it was only an 8 week study, research showed the 6 times per week should better gains than the 3 times per week in the following 3 areas:
Increase in FAT FREE MASS (HYPERTROPHY)
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- 6 vs. 3 times per week (+1.29% vs. +0.82%)
Increase in Strength – BENCH PRESS (1RM)
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- 6 vs. 3 times per week (+9.64% vs. +5.41%)
Increase in Strength – BACK SQUAT (1RM)
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- 6 vs. 3 times per week (+9.73% vs. +6.02%)
This is one of infographic of the training schedule:

Full credit – this study was reviewed and here is a link to the original PubMed article (Click here)