I get the Training Status feature is suggested guidelines to follow and to be taken with a grain of salt, but the following has me shaking my head. About a week and a half ago my status read "Maintaining". That was fine and based on my workouts, what I believe it should be. In a few days span I did a threshold run and two HIIT cardio workouts. My status dropped to "Unproductive", Low Aerobic Shortage. GCM was showing, "It looks like your training load is too focused on high intensity activities. Consider mixing in more low aerobic activities to be more productive." OK. This too made sense based on my recent workouts. So, yesterday I went on a very slow 3 mile run staying in my HR zone 2 and barely going in to zone 3. I still had the same message. I just went on a casual 8 mile bike ride never going higher than my zone 2 and now I'm getting "Unproductive", High Aerobic Shortage. "It looks like your training load is too focused on low intensity activities...... I feel like I'm trapped in a revolving door. 
