Last week, I swam in salt water. I went to a thermal bath with a 22m pool length and very warm salt water. I wore my Instabeat as well as my Polar watch and chest belt simultaneously to compare them. And as you can see in the graphs below, the expensive professional unit of Polar had to give up! What happened was that the Polar chest trap could not cope with the salt water.
This is a 1-0 for Instabeat!!
If you look at my curve, you can see a relatively high heart rate despite the fact that I wasn’t doing much effort. That was because of the high water temperature (which was of approximately 28 degrees Celsius). A reason to train with HF measurement is the ability of the body to have a faster heartbeat at higher temperatures under the same load. When you run in the summer in the sunshine, you can notice that same effect. Swimming in warm water is similar. In both cases, you will have to adjust your training load if you want to train effectively.
The next day, I swam in fresh water and my Polar belt worked fine. The curves of both devices were relatively identical except for two short zones where Instabeat went down to 40-50 beats per minute, which was determined as being too low.by