I don't know, but it was/is mostly in the anaerobic range (BPM).

It's worth googling around and reading about what the upsides/downsides to different cadence. It's pretty tough on ones legs/knees to be doing 1 hr of hard pushing every day. It may seem too high, but shooting for 80-90 rpm at lower gears is what pros tend to do, and if you try it you can feel the difference (limiting factor quickly becomes cardiovascular system as opposed to your leg muscles).

Did you mean aerobic range? It isn't physiologically possible to get most of your energy from anaerobic metabolism for efforts more than a few minutes long.

No, i meant anaerobic. This is a 1h bike ride from last week, a bit over 20 km: https://imgur.com/a/MkE3Oqe

Bold red line is BPM. Green area is "burn fat", red area anaerobic, in between aerobic, above anaerobic the "warning" area. White line is speed, usually going to 0 when I make a photo. Black line is altitude.

The peak you see at 9pm is at 172 bpm, I think I have 180 set as bpm max.

No, you are misinterpreting the chart or you have the zones configured incorrectly. If you don't believe me then go get a metabolic test at a sports medicine lab with a breathing mask and stationary bike.

You made me review the code

  hrmax = 178
  hropacity = 0.1
  g.append("rect").datum({y:hrmax*.9, height:hrmax*.8})
    .attr("x", 0).attr("y", function(d) { return yHR(d.y) })
    .attr("width", width).attr("height", function(d) { return yHR(d.height)-yHR(d.y) })
    .attr("fill", "rgba(255,0,0,"+hropacity+")");

data

  {"ht":"20:59:36","lt":1724439576300,"to":7200,"pr":"ble","sn":"hrm","sv":{"hr":172}},
  {"ht":"20:59:37","lt":1724439577350,"to":7200,"pr":"ble","sn":"hrm","sv":{"hr":172}},
  {"ht":"20:59:38","lt":1724439578399,"to":7200,"pr":"ble","sn":"hrm","sv":{"hr":172}},

maybe 178 is too low or I'm sick.

I have no idea what that code means but I assume it has something to do with maximum heart rate? The only way to know your actual maximum heart rate is to do a maximum effort test. This value will be activity specific: all else being equal, most people can hit a higher max HR when running than cycling because running recruits more muscles.

But knowing your max HR won't directly tell you the heart rate at which the majority of your power output is generated from anaerobic metabolism. There is only a loose relationship between those numbers, with significant variations between individuals. Again, if you want to actually know your numbers then you'll need to do a metabolic test in a real sports performance lab where they can measure inhaled and exhaled gasses while you pedal a stationary bike, along with data from power meter and HR sensors. Some consumer fitness trackers such as Garmin bike computers can also give you a rough estimate of heart rate zones based on your HRV response curve.

While I can't disagree with any of this... just riding at 80 RPM v 50-60 RPM (what a lot of amateur cyclists do) will make a difference on the legs and knees. You can feel it immediately, even at the exact same power output. There are various studies on it with all kinds of justifications involving oxygen usage and different muscles etc etc, but just try it and it's sort of obvious.