I'm in my early 50s and exercise to a max HR over 140 6-7 days per week. Most of that exercise is running: around 30-45 miles most weeks, but often supplemented by, or substituted for, a gym session on the elliptical anywhere from an average max HR of 110-140. I also hit an average daily step count of about 17K over the last 12 months. My weekly sleep average is around 7:45-8 hours per night as counted by Garmin.
My resting heart rate is around a 47 if I'm feeling generally good and in good health. That means no sickness coming on or heading out of the body. And no nights of excess alcohol consumption or running myself down, figuratively or literally.
This screenshot from Garmin Connect mobile shows a 46 resting rate from the week of March 13.
Sure, on a day to day basis the average resting heart rate can vary +/- 5 beats. I'm not freaking out from a 43 reading or even a 53 reading on one day. They happen regularly, and are usually one-off readings that don't occur on consecutive days. A night of 3 beers can do it, as can a restless night due to travel or racing.
If I start seeing my resting readings repeatedly drifting into the 50s over the course of several days, I will cut down my running and other exercise. I'll try and avoid hard and or super long (much more than an hour) workouts, keeping my exercising heart rate well below 75% (or around 140). And I'll keep my daily step count around 10K - no super long moving days allowed.
Two weeks ago, I noticed my resting rate creeping up to a 49. I had run near pr half marathons in the two proceeding weeks, which could have explained it.
And I did feel a bit off - fatigued and like I might be coming down with something. Sure enough, the night of the 27th, I started to have symptoms of a cold which I vainly hoped were just severe allergies.
The week of March 27, my resting rate went up from a 46 to a 51 average, a pretty significant increase for me.
Presented with some data, it was easier for me to take a few (5) days off from exercise, get more sleep, and try and recover properly vs running right through the sickness. I would have ignored my body at age 30, but it seems pretty pointless in my 50s where going down with a massive sickness has too much cost to work, family, and longer term running life.
It's also good to see five days off doesn't seem to have much of an impact on my pace or V02 max readings. I'm still sniffly, but the rest didn't hurt.