A story in Vox about 69 year old chronobiologist Robert Sothern’s daily recording of his own vital signs. Something he has been doing for decades:
“I measure my heart rate for a minute,” he tells me on a recent phone call. “I measure blood pressure. I measure respiration for two minutes, breathing slowly and counting how many times I inhale. I measure peak flow [air flow from the lungs], and I’m doing time estimation [counting to 60 without looking at the clock, and then seeing if it matches].” Fourteen years ago, he started to wear a step tracker.
Sothern notes the appearance of cycles in his data:
“We are rhythmic creatures,” Sothern, says. “You look at this … data [and] you can see 10-year cycles in it. You can see daily cycles. You can see even men have something approaching a 28-day cycle in their beard growth — which I did measure for three years too. By having a rhythm, it proves that you are alive.”
Check out Goolge Scholar to see some of his reasearch