But how'd you automate that? With this I mean there's interval timer programs like MTimer for doing precision intervals like that. As ProfileMatic is meant to automate different things without manually doing anything on the phone, and going to gym and starting an exercise is probably not something easily automated, how would such a rule exactly work with ProfileMatic?

I'm not trying to be difficult, it's just that as ProfileMatic is all the time running in the background, and having in UI possibility to give second precision for this, it could easily lead to battery draining.

It's not impossible I'd add that if I see a convincing enough real-life use scenario (having it hidden inside Advanced setting or something). In fact, second precision already should work, there's just no UI for it. You can manually edit ProfileMatic's configuration file and restart the daemon to have it. If you want to test it, just create your rule with the minute interval settings, and open ProfileMatic's configuration file. Find timeInterval settings, they're in seconds, and edit them how you want. Restart ProfileMatic daemon.