Today I ran my second of four marathon pace runs. I am running these at 6:45 as I have high hopes of breaking my 12+ year old PR. That is definitely a long shot, but you have to set high goals.

I was not originally planning on running this on my Boston Simulator course as it is quite hilly and I was worried that 12 miles at MP might be a bit much for me at this stage. Well, I managed to talk my wonderfully patient wife into letting me run at noon instead of my usual 5:50 AM start time. It was relatively warm (10 degrees) and sunny as I headed south with a good 10 MPH wind from the north behind me. After a 2+ mile warm up I was ready to start on my Boston simulator loop.

I was wearing my Garmin Forerunner 201 as usual and also the Polar S625X, with the foot pod. I have not calibrated it yet and was eager to see how its mileage compared with the Forerunner before calibration. Here are the splits:

Mile-------201 Split---------S625X Split---------HR
1------------06:25---------------05:46-------------165
2------------06:29---------------05:40-------------167
3------------06:44---------------06:12-------------170
4------------06:36---------------05:52 ------------167
5------------06:39---------------06:04-------------168
6------------06:42---------------06:14-------------168
7------------06:38---------------06:02-------------170
8------------06:43 --------------05:58-------------172
9------------06:57---------------06:24 ------------171
10----------06:47---------------06:14-------------170
11----------07:11---------------06:36-------------169
12----------07:00---------------06:22-------------171
Total------50:51

Obviously, the Polar S625X was measuring the miles short. When I first noticed this phenomena, in the first two downhill miles with the wind, I figured the Polar was just under estimating the miles on the downhills as it overestimated them yesterday up hill. I was also running much faster than yesterday, but I was hoping that would not have so much of an impact on the mile estimation. After all, who wants to recalibrate the foot pod for the pace of the day. In addition to the pace, I also changed the shoes (from the heavier Nike Pegasus to the lighter Asics GEL Flash) and moved the foot pod so it was lower down on my foot closer to my toe. If the movement of the foot pod to closer to the toe is the reason for the different measurement of distance and pace, then all is well. If it simply different from shoe to shoe or for different paces, then I think the S625X has some problems.

As soon as it warms up to above 14 degrees, I will try to isolate why the S625X's measurements seem to vary from run-to-run.

Anyway, more about the run. The first 5 miles, after the 2+ warm up, are generally downhill, although most of mile #3 is level with one slight uphill. Mile #6 is a very gradual uphill. At the end of mile #6, I turn around and head back. The first five miles went pretty easy, although I did not realize how strong the north wind was. Mile #6 was work and it was when I turned around and into the wind that I realized I was going to have a tough time staying under 6:45. At the end, my pace was exactly 6:45, although I probably pushed too hard and should have taken it easier.

My feet did hurt wearing the Asics GEL Flash. These are probably not going to be my marathon shoe.

Victor

Cross-training: 0.0 miles
Running: 16.5 miles
Shoes: Asics GEL Flash
WTD running: 60.5 miles
WTD total: 76.5 miles

posted by Not So Competitive Runner at 8:12 PM