I ran this morning. It was not a good run by any standards and really paled in comparison to my last run on the 2nd in which I managed to run 3 miles at an average pace of 9:54. This was a first at this pace and I was ecstatic! I believe I owe it all to my Heart Rate Monitor (HRM for short) and a completely distorted view of what my heart rate should be.
I had this idea that my max HR should be 180 beats/min. I have no idea where I came up with that but if you read about this stuff what you find is that the simple calculation is 220 minus your age (which would be 170 for me) and the more complex and perhaps slightly more accurate calculation is MHR=217 – (0.85 × Age) which for me would be 174.5 which isn’t that far off of 180 but still. You are supposed to train at some percentage of your maximum rate. I ran the super run at between 160 and 170 the entire time which is between 90 and 95% of my max. This is, perhaps, overkill and yet I felt great at the end!
This morning I decided that the sun was shining and it couldn’t be THAT cold so I went out in shorts and t-shirt with a long sleeved t-shirt over that. Fortunately I took the dog for a short walk first and realized that it was way too cold for that little outfit. There was frost on the rooftops and I could see my breath. I brought her home and added a hat and gloves to my ensemble and headed out to hit the pavement. I ran something over 3.5 miles (I had my Garmin turned off for a bit) but my average pace was 12:18. How much does that suck? My HR was up between 160 and 165 still but I do believe that if your thigh muscles are cold you just can’t bust a decent move. I guess it was naive of me to think that a distorted view of the temperature coupled with a distorted view of how fast my heart should beat would somehow add up to a great run. I think there is a life’s lesson in there – if only I could see it through all the distortion.
21st-century-mom.com 
Well, since I’m such a running expert, here’s what I have to say: somedays running sucks, and there’s no rhyme nor reason to it. And some days, it’s awesome! and there doesn’t appear to be any rhyme or reason to that either!The end.(Your next run will be better. You’ll see.) And as everyone is constantly telling me, at least you are out there moving your butt–which is more than 1/2 the country is doing!
The fact that you can run 3 miles is amazing, and that time is pretty good. It’s weird how some days a mile is agony and other days 12 miles feels like nothing. It’s good to monitor your heart rate, but don’t get too caught up in the numbers. My rule of thumb is that I should always be able to say my full address, out loud, while I’m running. If I can’t do this because I’m gasping, I’m running too hard and not really burning anything but the sugars I just consumed. This worked for me throughout track and cross country, and it is a good way to make sure you are regulating your oxygen properly too.