Tuesday, April 24, 2012


Last week I got a new (well, old, actually) Garmin 310xt in the post. Being a technology geek I could not resist a little experiment, so I ran with both Garmins strapped to my wrists. I expected the data to be more or less identical, but was quite surprised to spot the differences very early on in the run; 2 miles from home, they displayed a pace discrepancy of 4 seconds per mile, quite substantial. The difference then came down gradually and had halved by the time I was back home. As you can see from the screen shots, the reason for the discrepancy was the 310 measuring a longer distance than the 305. (I also found out that it is surprisingly tricky to take a readable shot of a Garmin's screen with a really bad camera when your fingers are frozen stiff, but that's beside the point. I apologise for the lousy quality of the pictures, though).

The next day I repeated the experiment, but swapping the Garmins round. Interestingly, this time the 305 reported a longer distance. This might indicate that I have an asymmetrical arm swing, or it could be just a fluke. Sadly I was prevented from examining the issue any further by the 305's sudden, if not entirely unexpected, demise. I have not managed to turn it back on, even though it is fully charged, so that little experiment has ground to an abrupt stop. At least I managed to time my replacement pretty much to perfection.

The best development is the fact that I can definitely feel the body bouncing back after Connemara. It took 3 weeks. I am not claiming that I am recovered, just that I can fell definite improvements. The heart rate data supports this as well, it has returned to values in the mid 140s rather than low 150s for the same effort.

There is a 10-mile race in Castleisland, 40 minutes drive from home, on Sunday that I was fairly tempted to attend, not least since the prize money goes rather deep into the field and I would fancy my chances of picking up something, but decided against it. As it turns out, Sunday will be a completely manic family day with all kinds of activities and I would not have had time anyway. Just as well. There are bigger prizes in store (though not monetary ones).

I didn't have any further car crashes.
23 Apr
10 miles, 1:17:12, 7:43 pace, HR 144
24 Apr
10 miles, 1:15:51, 7:35 pace, HR 146


  1. A tip re the Garmin Thomas,press the mode and reset buttons together for 10 seconds plus and try power up again.Worth a try.
    Best wishes Keith S.

  2. GPS signal for all mobile devices is min. 1% error (no. of satelites, weather cond. ...) so over 8mile run you should expect 0.08mile difference

  3. I'm expecting the first sub-60 10-miler from you Thomas! You've been doing plenty enough miles for it.

  4. Re Keith S comment - yes, I've heard that works. The 310XT is supposed to be pretty good, but all Garmin's usually show a course as being a little long - try running 5k on the track and you'll usually get at least 5.1k. The lady I ran with today has a new 900 model and the current pace is next to useless (big variations) - a tip is to set the 'lap' to a small increment - 100m and use that.

  5. I've already tried the mode & reset trick. It has worked plenty of times in the past but no joy this time. I'm pretty sure it's bricked :-(