Yesterday I took my Navigator for a long run to see how accurately it could predict a low. One of the main reasons I wanted a CGMS was to have a way to monitor my blood sugars during exercise without stopping, to have an alternative to finger sticks in the pouring rain (like IMLP) and to have a trend predictor of an impending low.
The plan was to run for 40 minutes yesterday at a recovery pace at then do hill repeats for 20 minutes. I knew my cumulative carbohydrate total was a bit lower than it should have been for the amount of exercise I've done over the past 2 weeks and thought there was a small chance I'd have a low, but was confident I had enough in the tank to finish the run. However, as I looked down at my Polar RS800 I noticed maintaining a 10:30 pace was WAY harder then it should have been (normally I run at an 8:40 - 9:20 pace), which is normally the first sign of a low. After struggling along for 3 or 4 minutes my navigator started vibrating, I took it out of my sleeve pocket and saw the vertical downward arrow and a blood sugar of 106 - it worked!
Yesterday, without the Navigator I would have kept running until my blood sugar was in the 60s since I normally test every 30 minutes while running. The Navigator predicted my low 4 minutes before I would have tested and allowed me to safely walk the rest of my route home - rather than having to sit down with an energy gel waiting for my blood sugar to rebound. The Navigator worked perfectly yesterday and prevented what could have been a dangerous low - exactly what I wanted the device for.