I have a very distinct memory of having my heart rate checked during a unit on the human body in elementary school – and having the doctor tell me, in no uncertain terms, that my heart rate was so low I was close to being clinically dead.
Fortunately I’ve always been a “roll with it” kinda gal, so instead of freaking out, I tucked that information away and asked my parents about it later. Turns out, I come by the freaky resting heart rate naturally, as my dad is bradycardic (defined as a slower-than-expected heart rate, generally at less than 60 beats per minute).
My RHR is right around 33 bpm, a fact that causes great consternation anytime I see a new doctor. Every night, my trusty Apple watch issues a warning about my low heart rate, and it is a serious struggle for me to get that HR up to anything over 130 – regardless of exercise intensity. And it looks like the tradition will continue, as my daughter had to see a cardiologist at the ripe age of 6 weeks due to an abnormally slow heart rate.
Of course, the fact that I run 70 miles/week exacerbates my bradycardia, and it is not uncommon for endurance athletes to experience RHR’s under 60 bpm. But is this a problem? Surely it’s better to have a lower RHR than one that is abnormally high. Generally-speaking, lower heart rates are associated with better cardiovascular fitness, so if you are going to be on one end of the spectrum, it’s better to err toward the lower side. But still, there’s a very good chance I will need a pacemaker later in life, I have a tendency toward lower-than-desired blood pressure, and I often feel faint when I stand up. My heart is quite literally the laziest part of my body.
But what’s normal, then? For the average healthy adult, a RHR between 60 bpm and 100 bmp is considered normal, though it is important to note than medical conditions (such as thyroid issues) and certain medications can affect this number.
If you are an athlete – or have every participated in a sport – you have likely heard of maximum heart rate. The traditional formula for determining this number is simply subtracting your age from 220. This formula is not wholly accurate for its simplicity, but it will give you a rough estimation for your heart’s maximum capacity. The closer you get to your maximum HR, the more your body will struggle to keep up with the physical demands being placed upon it. And, as you might imagine, your body can only handle so much time at that maximum level of effort.
Heart rate training can be a very useful training tool for many people in fine-tuning cardiovascular efficacy. For others, such as bradycardics like myself, it’s a bit more complicated. My maximum HR is approximately 180 bpm (please don’t do the math to see how old I am). Yet even during high-intensity speed work, I can’t tell you the last time my HR rose above the low 140’s. Is it possible? I won’t say no, but I train more by perceived level of exertion than HR. Similarly, I know people whose HR skyrockets to the 180’s the moment they start a slow jog and stays there at all intensities.
There is no reason not to give HR training a try, but be aware that there may be inhibiting factors, including individual HR variances and extreme environmental conditions (heat and/or cold), to consider.
That said, a quick summary of HR zones and their associated intensity:
Zone 1/very light intensity: <60% of max HR
Zone 2/light intensity: 60-70% of max HR
Zone 3/moderate intensity: 70-80% of max HR
Anything above about 80% puts you out of the aerobic zone and is increasingly – and quickly – difficult to sustain.
Zone 4/hard effort: 80-95% of max HR
Zone 5/all-out effort: 95% - maximum HR
Most people will spend the majority of their active time in zones 1-3 – and indeed, our bodies aren’t designed to spend a lot of time in zones 4-5. Regardless of whether you opt to train with an eye on zones or not, spending time in all HR zones is important for increasing your heart’s efficiency and maximizing your cardiovascular health.