yeah i used to do around 8 sets per muscle group but honestly it wasnt enough for me.. iw asnt growing like i should.. i upped it to around 16 and started isolating muscle groups giving each section so many sets and it has worked wonders.. the only problem is rest and stress... you need a lot of rest, good nutrition, and no stress... unfortunately i have stress, i dont get enough sleep, yet i focus on good nutrition.. so what i found to work best for me is hit the weights hard (high volume) for a week or two, then lower the volume at the site of overtraining, therefore since my body is used to higher volume the lower volume is almost like a rest week.. seems to be workin well..