3 of 6 Volume has been shown to have direct correlation with muscle growth.
3 of 8 INCREASE YOUR VOLUME
This means if you're doing eight sets of arms once per week and are getting no results, you need to up your volume. I recommend adding additional sets on another day a week for arms. I found training arms three times per week has been ideal for growth. An important point is to make sure you slowly walk your volume up over time. Do not just jump into three days per week without slowly increasing your volume otherwise you risk injury.
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http://www.muscleandfitness.com/athletes-celebrities/pro-tips/7-little-known-hacks-bigger-arms/slide/2
