I have run on an off for 35 yrs and have noticed when returning to running in last 6 mths after 5 yrs on "power" walking, actually just fast walking ie 14 - 15 min pace,, my normal HR is 30 to 40 so when I go out to jog I start walking fast and Hr gets to 60 to maybe 75. When I start to jog I have a natural pace of app 8 min, but I can't maintain that for more than 1/2 mile without slowing down and walking. I've tried to train through this, on/off walk jog of varring distances and pace for 6wks now, rarely I can make a contious 9 min mile then it's back to walk jog for remainder of my 4 to 5 mile routes,,, I find I can't run slow enough to run continuously without getting out of breath, my HR at the time I have to walk is about 125 - 130,, it just seems like after yrs of cardio my heart won't react to the traing effect anymore,, it's getting frustrating,, but with all that said I'm happy to be out there, any one else have any similar experiences, I've recently read about bradycardia ???