Have any way to measure your performance during these workouts? How many steps do you normally take? And how many did you take this time? If you were moving faster your HR would naturally be higher. A higher HR at the same perceived exertion and metabolic marker of nose breathing would indicate an increase in aerobic capacity. That’s a GOOD thing.
Hyperthermia would come along with a feeling of higher exertion and effort. So, I doubt that.
I hope this helps,