Dr. Betty Murray explains zone-two aerobic training, maintaining 120-140 bpm for women in their 50s, builds metabolic flexibility and insulin sensitivity. Long, low-intensity sessions once or twice weekly for 1.5 to 2 hours work better than frequent high-intensity cardio, which can cause muscle loss when overdone. Pair zone-two with strength training for mental health and performance.
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Foreign. Now, zone two training in a woman in her 50s is going to generally be somewhere between 120 and 140 beats, right? Beats per minute. And so. So when you're working at that level, it's harder to talk, but you can still talk, right? And that is a threshold. That's the lactate threshold. And it's very hard to tell. I mean, ideally we would have a lacta lactate meter to be able to see that, but we don't have, like, glucose meters, like lactate meters. And they're a little bit expensive to do and a little bit time consuming. But essentially, when you're in that zone two training, it's faster than you can walk, right? It's almost impossible to walk fast enough. Jogging or running, it often feels like you're not working hard enough. And people actually work run at a pace that's beyond that, closer to zone three. And cycling, it's a little easier to do this. Or elliptical or swimming, it's a little easier to do this because you're able to actually maintain a speed that increases this. Now, where does zone two come in? So zone two helps glucose utilization and mitochondrial activity, so it increases mitochondrial biogenesis. So that means in every single cell, we produce more mitochondria, right? So I'm building muscle fiber and producing more mitochondria. I become more metabolically active, my body becomes more efficient. And zone two, for it to be really, really effective, it needs to be longer in duration. And so this is one of those things that the longer you do it, the better. Me personally, I do one to two Zone two trainings a week, where I'm out on a bike for a longer period of time. And what's interesting about zone two, when you utilize it properly and you get into that heart rate zone, what you'll start doing is you'll start being able to take the heart rate to a higher rate, but do more fatty acid oxidation at that higher rate. So here's where the difference resides. When you're lifting weights, you're in an anabolic state. Your body is using glucose during that time, right? It is not burning fat. That is not what it's doing. But it increases fat burning afterwards, right? So it acts as a glucose sponge, increases fat burning capacity afterwards. Zone two is where you burn fat and you burn glycogen stores. So you burn through glycogen stores first and then you burn fat. What's interesting is when this is done properly with longer duration. So when I do mine, it's usually on the weekend, and I go for about an hour and 15 minutes to two hours, I'm on my bike. This is also my mental health thing. And what I have found over time is my threshold for zone two improves, meaning I can create a little bit higher heart rate but still stay in that fatty acid oxidation zone where I'm still fat burning. So what's really happening here is as you create more mitochondrial efficiency, you're better at burning fat and burning glucose at the same time, but you're not doing it to the extent that you burn off the muscle that you just tried to put on. When you're in zone three and zone four at extended periods of time where you're above that and you're not getting enough oxygen, you start to burn off the muscle you put on. And this is what happens with most of us that were in the aerobic Gen X world. We were, we were working out at a level that is beyond that capacity. And a lot of your high intensity interval like locations, your, you know, FT45s or whatever, or your orange theories often take their aerobic thresholds above this zone. And even though they've got weight training and other stuff in there, it is largely a high intensity interval activity that is actually cardio at the same time. While it may make you feel great, it may actually be counterproductive because it, it doesn't improve that muscle protein synthesis activity. And it also is beyond the fat oxidation level at that time. And so you're basically burning off muscle. And that happens a lot. I see a lot of women that have come to us at Minerva or my clinic for the last 20 years and they're working out like a fiend and they love this kind of exercise because it's great for the mental health. But they're like, I'm working my ass off at a, at a, you know, orange theory and nothing's happening. And this is why. So zone two needs to be at a slightly lower threshold, but a higher threshold than what you can do walking. Adding a weight vest often makes it better for, you know, mechanical load. Again, mechanical load. And there are studies looking at improvement in bone mineral density with weight vests. I've had one for 22 years. I love weight vests. It's, they're valuable, but again, they can't get into that zone two training now. So one really good zone two a week helps to start getting you there, especially once you've got the strength training. And you can always tell if you're in a good zone two is that you recover and the next day, you may be like, oh, I could do that again. You won't do it again, necessarily, but you could do it again. If you feel run down and beat up, then you were probably exceeding your zone two capacity. And that's a really good way to sort of see it. And this aerobic capacity increases your metabolic flexibility. Switching. Right. Your partitioning between glucose and fat and improves your insulin sensitivity and increases mitochondrial biogenesis. This is the big deal.
