Those are heart rate zones, high intensity interval training (HIIT) is zone 5. Here's the first description I found: https://www.polar.com/blog/running-heart-rate-zones-basics/
Since it's interval training, just doing 10mins hard is not what's prescribed. It's more like doing repetitions of, say, 2 mins easy and 30s sprints.
I would recommend reading about stoicism and mindfulness. For me they felt like those things that are obvious but are super helpful to see explicitly stated. And have helped me learn to enjoy life more and set priorities for where/with whom I spend my most precious resource, my time.
I couldn't take it anymore. After living for a while with the Element Hiding Helper for Adblock Plus, which allowed me to simply hide some of the stupid white space, this last change made Reader essentially unusable.
Today I switched to Bloglines, and I can keep using j, k, etc.
I have to thank Google, however, for making my switch so easy with their export utility...