Garmin Swim and Garmin Tri and their performance in the water.
What’s your experience with the Garmin Swim and Garmin Tri, and how do you use them for training and racing?
I have used Garmin HRMs in training for about the last five years, mostly running and biking but also for rock climbing, soccer, and kayaking. I use a 920XT and an Edge 520 (all the Garmin heart monitors will send info to both devices simultaneously). I have been doing triathlons for about 8 years. I am not all that serious about racing, but I enjoy destination races, training, and using HRMs as a training method. I also do a lot of adventure races, rock climbing, and mountain biking with my 8-year-old daughter. She did her first cyclocross race this weekend!
I bought the Tri about 2 months ago (right after it came out). The Tri works great for biking and running. It gives you all the same running dynamics (Cadence, Vertical Oscillation, and Ground Contact Time) as the Garmin running HRMs. I have practiced with it at Barton Springs and Lake Austin. It works great in the open water with or without a wetsuit. As far as races, I used it in the Cabo Ironman and the Austin Half. It's great not to have to mess with putting on a HRM during T1—one less thing to worry about. For me, it was worth buying for that reason alone.
As far as the usefulness of the HRMs for swim training and racing, I am still figuring it out. Everything I had read before said that your swimming heart rate was lower than your biking and running heart rate at the same perceived level of intensity. For that reason I had never really worried about my swimming heart rate but always wondered why it was so high at T1, then lowered on the bike. What I have found since using these HRMs is that my swimming heart rate is around 10 beats higher than the bike and slightly higher than the run at the same perceived levels of exertion. In addition, in races it sometimes hits 175 bpm—definitely not good for an Ironman! I still haven't fully absorbed this info, but it will certainly affect my training and racing.
How do the two HRMs differ? How accurate do you find them, especially for open water?
DO NOT expect to be able to use the Tri in a pool unless you don't push of the wall at all or don't mind cutting off the circulation to your lower torso. Even lightly pushing off the wall with the strap very tight, it slips down or flips over, which made it unusable for me in the pool. That's why I bought the Swim. I have gotten used to it being a little tighter than I would have preferred, and haven't had issues with it slipping/flipping off during flip turns. One other note: while training in the open water you can roll over on your back and the HRM will almost immediately sync with your watch (to check while swimming). Same with stopping at the edge of the pool.
The GPS on the 920 when swimming is not that accurate. The file shows me swimming on the shore half the time at Barton Springs. Granted, I was swimming at the edge of the pool, but still, it's a good 5-10 feet off. That said, this inaccuracy doesn't really bother me. When you are swimming distance in the open water the inaccuracies will more often than not wash out (no pun...) and who cares about a few feet or even a few dozen. If you really care, you can always attach your watch to a pull buoy.