[vasco]

Is there any reason for such strictness with your heart rate? I never measured anything and always progress up to a nice speed, and then it's when it flattens. Mix up the trainings and leave the HR monitor at home. Do ones where you just sprint as often as you can and others where you go slow, if you see some stairs during your run just sprint over them, etc. Of course, only if you're a regular person without existing heart issues.