well remember that overtraining is primarily a result of nervous system burnout. if you keep your training sessions short you can probably train more often. however on the flip side remember that larger muscles take more time to recover. but as for the muscle physiology you need to overload the muscle to achieve supercompensation, and this overload is not, should not be accomplished per training session but more intelligiently over a period of weeks or months. so periodicize it. ideally i like more frequent but shorter highly intense training sessions. ideally something like two times a day, 3 on, 1 off. then every 8 weeks or so take a week or so off. then maybe resume with eod training for six weeks. etc. you just have to mix it up. listen to your body. there are no absolutes if you learn to do this.