I’ve never been a deep data diver. The data that I know well includes my average resting heart rate (47) blood pressure (118/78) and how fast (or slow) I typically cover training miles.

After a six-mile run on Sunday, I swiped Left a few times on my Garmin readouts to view data related to the miles I’d just completed. The data on heart rate caught my eye.

What this shows is a chart of heart rate (red) across a six-mile run in which the pace ramped up to 7:14 at its fastest point with an average over the last four miles (or last 3/4 of the run) of about 8:30. I warmed up at 10:00, ran the second mile at 8:50, dropped to 8:25 the third mile, 8:18 the fourth and then started to feel it through the hills on the east side of the Fox River Trail.

My pace sank to 8:46 as fatigue caught up with me. But as you can see, the pulse rate stayed high except for that dip where I stopped to pee. It rose again to near 170 for the remainder of the run at 8:55 pace.

Important note: it was 76+ degrees at the start and finished near 86. Pretty hot, and heat accelerates the heart like nothing else. The hills were a factor too. You can see the impact of the climbs in this pace-per-mile (gray) versus elevation (green) data chart. That last big hump toward the end of the run is the rise through a forest preserve that ends with a 400 yard downhill onto the flats next to the Fox River.

While I didn’t sink to a complete jog, I could not wait to finish that run yesterday. The Zone chart tells why. I spent quite a bit of time in the Red Zone with a heart rate above 150 bpm, which is what I expected from a relatively hard effort on a hot day.

That’s how I like to go about things now and then. Train steady most of the time, and do about 20% overall at a harder tempo, including some speed.

My maximum heart rate these days tops out around 180. Or so it seems. I’m pretty sure that I could drive it above 200 in my youth during athletic prime. Running at sub-5:00 pace for six miles requires that kind of heart performance.

I’ll never know what my heart could do forty years ago because there was no such thing as a heart rate monitor. Tracking devices such as Smartphones and Garmin watches were not invented yet. All I had was my Timex watch and an index finger on my neck to determine how well my body was responding during training.

Sometimes I’d be close to sleep at night and would test my resting pulse rate. In 1984 when I raced 24 times at distances from one-mile to 25k, my heart beat just 38 times per minute. I can still recall its slow, consistent thumping.

Ten years ago during a period of high personal stress from caregiving, I felt some palpitations or fluttering sensations in my chest and worried that I’d developed arrhythmia or some other condition. I got checked out at the hospital and did a stress test on a treadmill that slowly raised the incline up to 18%. I ran steady for several minutes until the pitch became so steep that I began to struggle as my heart rate soared.

“When can I stop?” I finally blurted to the technicians. “Oh, anytime,” they answered. “You were done three minutes ago.”

They got their stats that day, all the data they needed to know that my heart was doing okay. Yet even those stats and data didn’t tell the whole story of a runner too dumb and obsessed to know when to quit.

That’s a lesson we seem destined to learn time and again.