Instead of HR, I count how many steps equals one full breath. As such, on an incline, I shorten my stride and slow down to maintain my breath per step count, thus maintaining a comfortable aerobic pace. I’m up to 45 min, with no post malaise. I also discovered that push ups seemed less problematic than faster walking; maybe because it involves smaller muscles, and a shorter workout, thus generating less lactic acid than fast walking used to. I started at 15, knees down, pushups; every other day. No malaise... My intent was to find ONE anaerobic activity where I could Improve, and get strong, without malaise. Keep you posted!