What if I offered you a pill that took your cellular age back ten to fifteen years? This pill also increases mitochondrial numbers (kind of like the number of battery chargers in our cells), increases overall available energy, improves metabolic flexibility, lowers resting heart rate, decreases blood pressure, and improves insulin resistance? This “pill” is yours for the taking, except we call it “zone 2 training”.
Zone 2 training occurs when we perform a steady activity while maintaining a particular heart rate for longer periods of time, say 45 or 50 minutes, twice or three times a week. It can be accomplished while walking, rowing, swimming, or working out on an elliptical machine or stationary bike. It is NOT the 30-minute class with the instructor yelling at you through the screen and leaving you staggering.
At this moderate level of training, you can still talk, watch TV, listen to a podcast, or watch some Tuscan scenery go by on a Peleton screen. Higher intensity has its role, which we will cover in another blog but high intensity done too frequently is a big mistake made by many people resulting in overtraining issues, such as fatigue, overuse injury, poor sleep, declining performance, and loss of motivation.
We also have to keep in mind our goals. If we are training for a specific event, we might push through to higher levels of intensity. But if longevity and optimal health is our goal, overtraining is not our friend.
Endurance exercise is somewhat of a U-shaped curve. Too little or too much is not good for us. Too little allows mitochondrial dropout, increasing insulin resistance with age, and gradually diminishing energy. Too much, especially paired with inadequate recovery and improper nutrition can cause early heart failure, arrhythmias, long periods of high adrenaline, and high cortisol which age us faster.
So how do we find our zone 2 sweet spot? First, we start by calculating our maximum heart rate with this formula: 208 – (0.7 x age). We then take 60% of this number as our minimum and 70% as our maximum (so multiply this number by 0.6 and then repeat using 0.7). For me, at age 60, my calculation is a range of 99 to 116 BPM (beats per minute). If you are on any significant medication for blood pressure, lipids, or any other serious cardiac or pulmonary issue, you might want to lower both numbers by about 10 BPM. If you are a fairly active athlete, you may have to index higher. It’s important to note we can’t study every person in a metabolic lab which is why we have to estimate our desired heart rate.
We then test out this range using a heart rate (HR) monitor (Apple Watch, Fitbit, Garmin, and others) and see how it feels. You should be able to speak a full sentence, and we often describe this as “I can go all day” intensity. At this level of exertion, you are building an aerobic base, the same way that triathletes and professional bikers do, with 70% of your training time spent at this intensity. You are also reaping the benefits of a level targeted to maximize fat burning over carbohydrate usage. If you follow your nighttime HRV (heart rate variability) on something like an Oura ring or a Whoop or Halo, you should notice a slight increase over months (allowing for day-to-day variations) indicating less strain on your system, and improved nervous system “tone”.
So turn off the spin instructor, and turn on a scenic ride, a podcast, or call a friend and enjoy your workouts again instead of dreading them. Two or three times a month you can still enjoy your 30-40 min sweat session. Longevity is the name of the game!
Here is a Garmin record of a zone 2 day for me:
Please note: elite athletes should consult a professional trainer, and use either Joel Friels LHRT test (https://joefrielsblog.com/quick-guide-to-training-with-heart-rate-power-and-pace/) or use the HRVlogger app and chest strap, shooting for alpha 1 of 0.75 or slightly higher (https://www.marcoaltini.com/blog/heart-rate-variability)