Heart Rate Running

Hi, new to the forum so please bare with me.

I have recently started running again after a considerable lay off. I am a reasonably fit 23year old I have stayed in shape through weight training and cross-training due to ITBS which I have just recovered from. I have been building up the distance I run in time size pieces and tomorrow I will be running for 60minutes, hopefully pain free.

I have a running schedule of day running and a day rest inbetween. I wear a heart rate monitor also. I have ran every time, so far up to 50minutes, with my average heart rate at 180bpm. I have no lactic acid buildup im not clambering for air and im not falling off when I have finished my time. It feels like a comfortably hard run. I feel strong throughout and not completely finished.

My question is this: Is there anything wrong with this sort of training? And why does it tell me everywhere else on the internet that 80-90% is anaerobic and should only be trained in for minutes at a time due to the lactic acid buildup? Wont I get fitter and faster quicker if I can train at 85-90% heart rate 3 times a week?

"The area between the top of the aerobic threshold and anaerobic threshold is somewhat of a no mans land of fitness. It is a mix of aerobic and anaerobic states. For the amount of effort the athlete puts forth, not a whole lot of fitness is produced. It does not train the aerobic or anaerobic energy system to a high degree. This area does have its place in training; it is just not in base season. Unfortunately this area is where I find a lot of athletes spending the majority of their seasons, which retards aerobic development. The athletes heart rate shoots up to this zone with little power or speed being produced when it gets there."

Matt Russ, US International Coach