Transcription
You've been told that the biggest zone 2 mistake is going too hard and crossing over into zone 3. But unless you're a high mileage runner logging upwards of 65 to 70 km a week, that's not your real problem. The real problem that holds you back, especially if you're a runner over 40, are the seven lesser-known mistakes I'm about to share with you. And even after running thousands of kilometers in zone 2 in my late 40s, I still catch myself making these mistakes.
Mistake one, treating zone 2 heart rate as gospel. Most people don't realize this, but heart rate is just a proxy for zone 2, not the real thing. The true definition of zone 2 is based on two physiological markers: blood lactate levels and the fat to carbohydrate crossover point. Here's how it works. At low intensities, your body burns mostly fat and produces very little lactate, which can easily clear. But as intensity rises, you start relying more on carbohydrates, which produces more lactate. Once lactic production exceeds your body's ability to clear it, it begins to accumulate. This tipping point is called your first lactate threshold or LT1, typically around 2 millimoles per liter. It also marks a crossover point where fat burning gives way to carbohydrate utilization, and it defines the upper limit of zone 2.
Now, pricking your finger mid-run to measure lactate isn't exactly practical. So researchers began correlating lactate data with heart rate. They found that for most people, LT1 corresponds with a fairly consistent heart rate range. Hence, heart rate became the proxy for zone 2. But here's the catch: heart rate isn't fixed. It changes daily based on things like temperature, caffeine, sleep, hydration, stress, and even what time of day you run. And after age 40, age-related changes in the autonomic nervous system make it even more unpredictable. That's why it's a mistake to treat zone 2 heart rate as gospel. Don't worry, I'll offer you some ways to solve this later in the video.
Mistake two, overrelying on wearables or on heart rate formulas. Now, what's even more misleading than treating zone 2 heart rate as gospel is overrelying on the zone 2 heart rate ranges estimated by wearables and generic heart rate formulas. Smartwatches are, well, very smart and very accurate, but they may not be accurate for you. Chorus, Garmin, Cola, Sundto, Apple Watch, and Whoop typically calculate your zone 2 range using your estimated maximum heart rate as a foundation. So, unless you've tested your actual maximum heart rate, those estimates can be way off. For example, my tested maximum heart rate is 181 beats per minute, but most formulas put me at only 174 to 176 beats per minute. And generic formulas for calculating your zone 2 range, like the MEF 180 or Carvin formulas, are helpful starting points, but they don't account for your unique physiology, training history, or even the sport you're doing. Two runners of the same age might have very different zone 2 ranges, and your zone 2 heart rate can also vary depending on whether you're running, cycling, or cross-country skiing because different muscles produce and clear lactate at different rates.
So, how do you solve these problems? The easiest fixes for mistakes one and two are the talk test and RPE, or rate of perceived exertion. If you can speak in full sentences while running, you're likely in the right zone. And on a scale of 1 to 10, you can rate your perceived exertion. Zone 2 usually feels like a four or a five: light to moderate, but never breathless. These are effective, free tools that can complement your zone 2 heart rate ranges and smartwatch readings. But if you want more accuracy, the gold standard is getting a lactate threshold test done where your blood lactate is measured at increasing intensities. And when it hits 2 millimoles per liter, which is your LT1, you can accurately pinpoint your zone 2 heart rate based on your blood lactate concentration. However, lactate testing can be expensive and not always practical. So, combining heart rate, talk test, and RPE together might be the most realistic way to dial in your zone 2 training.
Before we go on to the next mistake, I have a question for you: Have you made any of the above mistakes? I know I have. I relied too heavily on the math 180 formula when I started. Let me know by dropping a comment below. I would really love to hear from you.
Mistake three, underestimating minimum duration for adaptation. Dipping into zone 2 for 15 to 20 minutes per session isn't enough for meaningful adaptation because it takes about 15 minutes for our fat metabolism and aerobic system to ramp up during exercise. So, to get the most out of your zone 2 training, sessions should last at least 30 minutes. And for the better-trained athletes, 45 to 90-minute sessions are needed to continue adapting. If you have limited time, you will benefit more by doing fewer zone 2 sessions per week, but doing each session for a longer duration. So instead of doing 5x 30-minute sessions per week, aim for 3x 50-minute sessions weekly. This strategy will offer you better time efficiency and more meaningful adaptations.
Mistake four, mismanaging training volume. Too little or too much too fast. One common mistake in zone 2 training is expecting meaningful results from too little volume. Zone 2 is a low-intensity to moderate-intensity stimulus. It's gentle on the body, which makes it sustainable, but that also means it needs a higher volume to be effective. However, once people realize that they need more volume, they often make the opposite mistake, and that's increasing training mileage too rapidly. This can lead to overuse injuries, especially in runners over 40, where connective tissue adapts more slowly than cardiovascular fitness. I fall into this camp, and in fact, I still make this mistake to this very day. I very often feel that my heart and my lungs are ready for additional work, so I add more volume. But then I realize that my tendons, ligaments, joints, and running muscles need more time to catch up, and I get injured. So, too little volume wouldn't yield results. Ramping up too fast can lead to injury. The key is progressive overload. You can adopt a well-known 10% mileage increase week over week, but that should only be a rule of thumb for two reasons: one, a 10% increase for a runner running 10 km per week is vastly different from someone running 100 km per week. Two, every runner's ability to adapt to training stimuli is different. I feel that the best approach is to listen to your body when increasing mileage. Push yourself towards progressive overload, but pull back before you feel that something in your body is breaking down.
Mistake five, going too easy. You've often heard about the ineffectiveness of going too hard during a zone 2 run, but going too easy can just be as ineffective. If your heart rate is too far below your LT1 or fat to carbohydrate crossover, you're likely in zone one. While zone one has its place, usually for recovery runs after a hard workout, it won't trigger the same aerobic and endurance adaptations as zone 2. Here's why it matters: high-intensity workouts deliver fast fitness gains, but they also carry a high risk of burnout and injury. Zone 2, on the other hand, hits the sweet spot. It's the highest intensity you can sustain before lactate builds up and fatigue sets in. It's low stress, but it's still productive, allowing you to accumulate much more training volume than you could with high-intensity work alone. And that volume is what toughens your entire system, from your connective tissue to your muscles, your cardiovascular system, and your mitochondria. It also builds resilience in your joints, improves your running efficiency, and expands your aerobic base. But if the intensity is too low, it doesn't create enough stress to stimulate any meaningful adaptation.
Mistake six, mixing intensities during zone 2 runs. You've probably heard that the 80/20 training principle, with 80% at low intensity and 20% at moderate to high intensity, is the gold standard for building endurance and performance. It lets you reap zone 2 benefits while still getting faster and stronger. But if you're time-crunched and try mixing the 80/20 into one single session, like stacking hill sprints into a long run or hitting the gym before a zone 2 workout, that's where things start to backfire. Zone 2 training relies on steady aerobic metabolism, which is burning primarily fat and driving mitochondria growth. But when you add intensity, your body shifts into anaerobic metabolism, burns carbohydrates, spikes lactate, and disrupts the metabolic signaling that builds your aerobic engine. Once lactate rises too much above the upper limit of zone 2, it can take 20 to 30 minutes to settle back down into a fat-burning state, meaning you lose a big chunk of effective zone 2 work and end up wasting valuable training time. And it's not just during the workout. Doing a hard session within an hour before a zone 2 run keeps your physiology revved up and compromises the next session, too. The best approach is to keep your zone 2 runs clean. If you must double up, either separate your sessions by at least 3 hours or do your zone 2 run first and your hard effort later.
Mistake seven, underfueling for zone 2 runs. This is probably the biggest mistake I made. I used to think that since zone 2 running primarily burns fat, running fasted would be perfectly fine. After all, even the leanest elite runners carry at least 30,000 calories of fat, more than enough to fuel over 40 hours of zone 2 running. I also believed that running fasted would accelerate my fat-burning engine. But I realized that I couldn't have been more mistaken. Adequate pre-run fueling is needed to stabilize your blood sugar levels and improve mitochondria signaling. Plus, faster training doesn't burn more fat. The way to increase your fat-burning capacity is by building more and better mitochondria because the only way fat can be oxidized is through the mitochondria. And zone 2 is one of the best stimuli for mitochondria growth. Underfueling will reduce your blood plasma volume, compromise your performance, and slow down adaptations at best. And at worst, it triggers hormonal stress responses that can slow recovery, break down lean muscle, and over time lead to issues like disrupted metabolism and hormonal imbalances. For this reason, women especially should avoid fasted cardio.
So, if fat loss is your goal and the tool you're using to achieve that is zone 2 running, a smarter approach is to properly fuel for your run while creating a caloric deficit in your overall daily intake. In other words, eat before your run to properly fuel the effort so you can train and recover properly, and then lose fat by eating fewer calories overall during the day. You're basically just rearranging when you consume your calories so your workout is effective and your fat-burning goals are also met. Based on current scientific research, a small pre-run snack containing 10 to 15 grams of protein and 70 to 100 grams of carbohydrates is enough to fuel a 1 to 1.5-hour run in zone 2.
If this video helped you rethink your zone 2 training, drop a comment and let me know what's the first thing you're going to change. Remember, zone 2 training works wonders, but only when it's personalized, consistent, accurately executed, and understood beyond just a heart rate number on your watch. But before you click off, please hit the like and subscribe button below. It prompts the YouTube algorithm to show this video to more runners who could use these tips.