Simply disagree on the over training topic. I'm in the gym an hour and a half as it is. By the time I get through my run training I'll be running another hour to two hours depending on the scheduled training day. Add in a biking training session a couple times a week of 20-40 miles and you've got over training issues. Your muscles need time to recover and repair, that's how they grow. Doing arms 4 days a week doesn't sound like a good idea to me. JMO
Ever worked a labor intensive job that required you to use your legs or arms extensively? If you are lifting and pull etc for 40 plus hours a week you may notice that your forearms or calves etc seem to be sore quite a bit. You would also notice that your body adapts and you end up with more muscle mass in these areas.
Lifting arms for 4 days a week for 6 weeks will do no harm. When I'm ingesting 250+ grams of protein per day and loading up on BCAAs with a properly balanced post workout meal/shake.
An average lifting session for me runs between 1.5 to 2 hrs. Are you telling me that at max using my bis and tris strenuously for 8 hrs a week is Overtraining? That is at most 1/12th of the allotted time in 4 days. Overtraining in regards to lifting weights is a bunch of bullsh#t for people that don't wanna put in the hours to push themselves to that next level. Buncha bon bon eatting pussies