I dont think its overtraining but everyones body is different. I usually do a warm up then do 6 sets with 6-8 reps. I try to focus more on form than lifting heavy. If I go too heavy my form is bad even if i accomplish the same sets and reps and that doesnt give me as good results. I would have to agree with everyone here that you should focus alot of compound exercises. Compounds, form, and time is all you need.