That is a very high (scary?) percentage of maximum heart rate to hold for that long. I’ve heard of holding ~90% of maxHR for ~2 hours, but 98%? That seems really high. Especially if it felt like a normal hike intensity, you may want to see a doctor.
Or perhaps your real maximum is higher, but I would still see a doctor first. You don’t want to do a maximum treadmill test if you have an underlying heart condition.
- You said you thought your max HR was 190. How was that 190 determined? By a metabolic test in a lab? Or just personal experience? If the former, it’s reliable. If the latter, then it’s not; your true max may be higher.
- If your max HR was determined in a lab, then I would see a doctor. 98% of maximum sounds dangerous, and perhaps there’s an underlying issue.
I hope that helps.