I’m still having a hard time understanding what “chronic high level training” is, exactly. How much is too much? Is there a heart rate zone you guys can give me? A time limit? Am I overthinking this??
Thanks, Charlotte, for posting this question  last week. As is so often the case, another MDA reader (hats off to you, Mike OD!) offered great advice. We thought the question was well worth revisiting. First off, let’s investigate the concept of chronic cardio. Intense cardio as we commonly think of it today means long stretches at a sustained heart rate in the 80+% range.
The fact is, our hunter-gatherer ancestors didn’t ramp up their heart rates significantly for over an hour every day, and I don’t think we should either. They walked at a very low level of exertion, burning almost entirely stored fats. Once you get into the zones where less fat is burned and where there’s a big dependency on glucose to fuel muscles, your body goes into a less efficient mode of fuel oxidation. There are biochemical costs associated with this shift. Your muscles and liver can only hold 500-600 grams of precious glycogen (stored glucose) at any one time, which means about 2 hours’ worth for the best trained individuals and less for most people. That means that to come back and work out hard the next day requires at least 600 more grams of carbs every day. That’s just too much glucose and insulin to deal with every day.
I don’t recommend pushing this limit or even approaching it. Why bother? This kind of training (and diet) raises cortisol levels, increases oxidative damage, systemic inflammation, depresses the immune system and decreases fat metabolism. About the only thing good it does is improve cardiac muscle strength – and even then you get too the point of diminishing returns fairly quickly.
As you know, I recommend a different approach that more accurately mirrors what we evolved doing. In those simpler (but not really “good old”), primal times, we spent several hours a day engaged in low level activity. A few times a week, caveman/woman life required brief spurts in high intensity anaerobic mode to run from various predators, hunt down dinner, engage in “play” etc. Each of these modes resulted in its own unique and very positive growth response.
This pattern, for most of us, isn’t easily replicated as a result of our busy lives. Instead, I suggest anywhere from 30 minutes to an hour of low to moderate level aerobic movement such as walking briskly, hiking, cycling, etc. It doesn’t need to be every day, but at least a few times a week is important. The goal during these sessions is to maintain the zone that burns mostly fat. For very fit people, this could be as high as 70-80% of your maximum heart rate, but we’re really talking 60-70% for most people. The benefits of exercising at this zone are numerous and the risks minimal. It’s the ideal level of activity for decreasing body fat, increasing the capillary network, and for lowering blood pressure and reducing risk for degenerative diseases, including heart disease.
Add to this routine a few anaerobic, “interval” workouts once or twice a week. Weight-bearing, anaerobic bursts are the best training for building muscle, and lean muscle mass is critical to health. It also increases your aerobic capacity, natural growth hormone production and insulin sensitivity.
Traditional running sprints  are one option, but we presented several others  last month for your perusal. Put your all into it for 20-40 seconds and then rest for two minutes or so between “sets.” You can start out with three or four bursts and work your way up to as much as eight. As always, get in some warm up time and stretches afterward. It’s no fun pulling a muscle.
Finally, working all muscle groups through dynamic strength-training sessions (ie: lifting weights) a few times a week helps further build and maintain muscle mass, insulin sensitivity and growth hormone release.
Finally, let me add that I’m not trying to squash anyone’s passion for competing. As a former competitor myself, I totally “get” the drive to compete. Do I think that mode of existence is healthy, particularly in the long run? Not really, but I still understand what brings people to it. I simply want to convey that certain and sometimes significant health compromises are inherent to competition training. If anti-aging, longevity and robust excellent health are your primary goals, high-level training isn’t the best way to achieve them.
Now, for those who aren’t into the competition mission, you have the advantage of making your fitness routine and health about ideal balance. And I’m a true believer in achieving the balance that allows people to live the longest, healthiest lives possible. Thanks for your questions, and keep them coming!
Abraaj  Flickr Photo (CC)
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