Pay Attention to the Resting Heart Rate on Your Smart Watch
Why knowing your personal norm can help you keep tabs on your health
“According to my Fitbit, I’m probably going to die soon,” I informed my husband.
“Probably from stressing about those numbers,” was his not completely unreasonable response.
“Those numbers” were my resting heart rate (RHR), the number of times a heart beats in a minute while the body is at rest. My Fitbit told me it seemed high, around 85 beats per minute (bpm). “Poor,” the smartwatch declared about my overall cardiorespiratory fitness.
I found that hard to believe considering I regularly log well over 10,000 steps chasing after two little kids all day long. How accurate are the health metrics on my smartwatch and how seriously should I take them? I worried and wondered. While seeking out the answers to these questions, I discovered that RHR is more than a potential window to health. When combined with wearable fitness technology, it could also have an unexpected but timely role during the pandemic.
For years, studies have shown an association between a high RHR and risk of illness or mortality. The link makes sense: a lower RHR would imply that the heart is working more efficiently. Think of the oft-cited example of super athletes with their fabled RHRs in the 30s or 40s. Athletes have a higher vagal tone, meaning increased activity of the vagus or the “rest and digest” nerve, and that means lower RHRs, explains Elaine Wan, MD, assistant professor of medicine in cardiology and cardiac electrophysiology at Columbia University Medical Center and attending physician at New York Presbyterian Hospital.
It’s not only athleticism that affects RHR, though. Wan points out that pregnant people will have higher RHRs because their hearts are working harder to provide blood flow and nutrition for two. Air temperature can also prompt a shift in RHR. “When it’s very cold, our vessels tend to constrict, which changes how much your heart will have to pump” to keep the body stabilized, says Wan. “These vessels are more relaxed in the summertime because it’s warmer.”
The bottom line is that “there’s a lot of variability between individuals and it would be inaccurate to say that…