HRV and VO2 Max – 2 Vital Readings that Most Medical Exams Don’t Test For (But Should)

If you’ve read some of my previous articles, you may know that I have written about both of these measurements of health, especially as they apply to later-life health. HRV (heart rate variability) measures the slight difference between the intervals of your heartbeat and can give you a reading on how rested and ready your body is to exercise on any given day. But it is so much more than that, as I write about below. The second measurement, VO2 max, is the maximum amount of oxygen your body can use in intense exercise. This reading serves as an indicator of cardiorespiratory fitness—how efficiently your heart, lungs, and circulatory system transport oxygen to your muscles, and how efficiently your cells, and the mitochondria inside them, use it.

Both readings are highly correlated to health and longevity. So, this is a mystery to me: Why aren’t they part of every health checkup as well as regular monitoring? Keep reading to learn more about these health measurements and see why I believe both are useful and informative for our health journeys.

Heart Rate Variability (HRV)—More Than Just a Fitness Reading

The growing popularity of measuring your HRV can be traced to its ability to predict how ready you are to exercise, or rest, on any given day. Originally discovered as a measurement that could be used in the training of Olympic and other world-class athletes, one aspect of HRV is a measure of how “recovered” your body is from the previous day’s workout. HRV trackers do this by measuring the time interval and electrical impulse difference between the sympathetic (when the heart beats) and parasympathetic (when the heart rests in between beats). If your parasympathetic (resting) phase is high, your body is ready for more work. And vice versa—when your sympathetic side is higher, it is sign that your body will have trouble exerting itself because it is not fully recovered from a previous workout or another type of physical exertion.

I have found this reading to be very valuable, and I take mine every morning. (My average “baseline” HRV is around 60, which puts me in the 90th percentile for a 45-55 year old.) Frankly, I have come to trust HRV as much as a “how I feel” internal check, and it sometimes gives me information that I find quite useful in determining how hard or how long to exercise that day. But I’ve noticed something else that most people who use HRV trackers rarely mention. I’ve done more research on this aspect and here is what I’ve found.

Think about how wonderfully sensitive your heart really is. It doesn’t only respond to physical prompts. Your heart rate will increase with fear, stress, desire, sleeplessness, overeating, excitement, or many other things. Similarly, it will slow down and relax when you feel safe, loved, content, happy, or rested. It is wired into the fundamental physical and emotional fabric of how the body operates. HRV is a deeper measurement of these states. I’ve discovered that HRV tells me as much about my emotional state, or mood, as it does my physical one. On some mornings when I am stressed, either by an external event (“the fridge is on the fritz again”) or internal negative emotions (“I regret what I wrote in that email”), my HRV reading can be lower, despite knowing that I’ve gotten plenty of rest and have recovered physically from the previous day’s workout. The research I’ve done bore this out.

My hunch was correct. A lower HRV measurement indicates higher emotional stress, not just your physical state, and can correlate with anxiety, worry, and lower levels of confidence. A higher HRV rate indicates more resilience and more confidence. So, HRV readings can indicate much more than just cardiovascular and physical health. By measuring the resilience of the overall autonomic system—the system that keeps you alive and healthy without you being aware of it—the HRV measurement is an important indicator of how the whole health system inside us is operating.

Here are some other important points I’ve uncovered in my research:

1.    Lower HRV readings have been increasingly linked to higher mortality rates across all age groups.

2.    HRV rates decline with age, but longer-living people and healthier people maintain higher rates. (Centenarians have exceptionally high readings, but when a precipitous drop happens in their HRV rate, they usually die within a year.)

3.    People with higher HRV rates almost always have a lower biological age than their chronological age. In other words, a healthy person who is actually 70 years old may be biologically similar to a person who is 60 or 65 years old—or even younger.

4.    In addition to inadequate recovery after a workout or other type of exertion, the factors that can most quickly lower your HRV rate are overeating, too much alcohol, and poor sleep.

5.    Sometimes I find that my HRV reading improves by early afternoon despite a low reading in the morning, indicating that a quiet morning can enhance recovery.

6.    The best way to increase your HRV rate is (you guessed it) exercise, especially aerobic exercise, along with better sleep, less stress, and a healthy diet. Sound familiar? Nature has been working on health and recovery a lot longer than we have. HRV is best used along with your own highly developed sense of “how do I feel?”

VO2 Max – The Newly Accepted Best Health and Longevity Indicator

While many doctors and medical facilities still don’t test for VO2 max, a growing number of health journals are reporting that it has become the best indicator of current health and predictor of later-life health and longevity. Like HRV, it is so much more than just a heart health indicator.

Let’s start by breaking down exactly what VO2 max means: "V" represents volume, "O2" represents oxygen, and "max" signifies the maximum rate of consumption (of oxygen) during peak effort. Remember that oxygen is the fuel that gives you energy for all the other wonderful functions your body performs to keep you alive and healthy.

Your VO2 max reading reflects how well your body is moving and how much blood is getting to your vital organs. In addition, it can indicate how well your immune system is maintaining your health. For example, a higher VO2 max reading indicates superior cardiorespiratory fitness, which is linked to a robust immune system.

As I’ve mentioned in a previous article, many fitness trackers have VO2 max readouts, but the gold standard is a treadmill stress test under supervised conditions, preferably hooked up to electrocardiogram (ECG) and blood pressure devices. My recent stress test also included an ultrasound, which my cardiologist used once the test was finished to “look” at how the muscles in my heart were beating.

How can you achieve cardiorespiratory fitness and a high VO2 max reading? Regular Zone 2 cardio workouts are the foundation to achieve a good VO2 max. Adding High Intensity Interval Training (HIIT) sessions, which increase your heart rate to at least 85% of your maximum heart rate, work in tandem with Zone 2 training to increase your body’s oxygen efficiency and your VO2 max.

I was recently a guest on David Stewart’s podcast, SuperAge, and Dave likes to say that increasing your VO2 max with a HIIT workout once a week is “exercise worth sweating for.” His favorite workout is what he calls a Norwegian 4x4: 4 minutes of intensive effort followed by 4 minutes of recovery, repeated 4 times. You can find many variations on this theme online, many involving shorter durations and more reps. The important thing is getting your heart rate to at least 85% of your maximum heart rate for as long as you are able to sustain this effort (safely, of course).

If you’re serious about your health, especially about later-life health and preventive care, I recommend adding these two metrics, HRV and VO2 max, as part of your health journey. HRV is easily measured, with many apps and devices available. (I recommend using a device with a chest strap as the heartbeat source since it is much more accurate than wrist-based ones.) Learning your VO2 max, measured in a stress test, requires a bit more effort and expense but is worth it from time to time.Both of these readings correlate closely with healthspan and lifespan, and they can offer helpful insights to guide your health journey, so you can enjoy a vibrant life for as long as possible.