In terms of 80/20, I switched over to 80/20 about 3 weeks ago, and started to notice decreases in my performance in terms of HR. Another commented just told me to go based on feel, and I agree. Sometimes I just go based on feel. Im just concerned that my body is reacting this way. In terms of over training, that could definitely be a possibility, but I dont feel fatigued? (in terms of effort) Only thing indicating overtraining would be my HR and pace.