Aerobic activity will kill you. Aerobic activity will give you a heart attack. Aerobic activity will deplete your sex hormone levels and age you. Aerobic activity will waste away your muscles. Don’t do aerobic activity!
Headlines such as these have been circulating like wildfire lately. I’m not sure why there’s more now—perhaps it’s due to the huge increase in people running half or full marathons (I’ll get to that in Part V of this series). Several CrossFit aficionados and various well-known personal trainers are anti-aerobic, and they feel that you have to kick your own ass day in, day out, to achieve results (strength, power, and a ripped body). I’ll give you my take based on personal experience, professional experience, research, and knowledge gained from those who know more than me about various subject matters. Whether you’re an endurance athlete, strength athlete, or a little bit of both, I hope there’s something you will learn. Even though I come from a deep endurance background, I’m not going to say aerobic training is the ideal way to train all the time (because it isn’t). But aerobic exercise sure isn’t going to wreck your health and strength if done properly. Actually, it’s the opposite. There’s a time for it all.
What Exactly Do You Mean by Cardio?
To start off with, most people use the word cardio to describe what they think is aerobic conditioning. A “cardio” activity can be either aerobic or anaerobic, depending on the level of effort and exertion required for that individual to do the exercise. Often, people train “cardio” anaerobically, meaning they exercise at a high intensity. These people have neglected to develop a key component of their health and fitness—the aerobic system. Calling anything endurance “cardio” is just as wrong as calling everything you lift, carry, or throw “weight lifting.” It’s a generalized, nonspecific term. Just as cardio can mean walking 100 meters or running a marathon, weight lifting can mean carrying your laundry from your washroom to your bedroom, or it could mean deadlifting three times your body weight. So let’s talk aerobic and anaerobic when it comes to “cardio.” If we don’t, I might have nightmares of Richard Simmons in his running shorts. Nobody wants that.
Aerobic Capacity: Building a Solid Foundation
Your aerobic system provides a solid foundation for good health. It is the system that predominately moves you efficiently through the day as these muscles support your overall posture. Training your aerobic system will increase mitochondria in your muscle cells to generate energy (ATP) and increase capillary vascularization for increased oxygen utilization. These mitochondria burn fat and glucose (sugar), but they’re much more efficient using fat as energy over glucose—12 times more. In general, type I, red, slow-twitch muscle fibers are aerobic and primarily burn fat for energy.
Aerobic conditioning is also a necessary foundation for virtually all training. Some exceptions could possibly be made for sprinting less than 200 meters (one time, no repeats), but most activities or sports are best performed with a well-developed aerobic system. The longer an event, the more your body will rely on the aerobic system. A strong aerobic base will even benefit one’s recovery in between sets of strength training as well as anaerobic interval training.
Many people, especially many “athletes,” are running long distances with a very poor aerobic system, relying heavily on the anaerobic system to get them through the training. This anaerobic training is their “cardio,” and it’s very, very unhealthy, which is partially why so many point to cardio as harmful to one’s health, especially when it comes to the immune and hormonal systems. These anti-aerobic “cardio” gurus cite studies, such as the one in the Canadian Journal of Applied Physiology from April 2004, “Intensive Swimming Exercise-Induced Oxidative Stress and Reproductive Dysfunction in Male Wistar Rats: Protective Role of Alpha-Tocopherol Succinate,” to back up their claims. Well, if you’re making a rat (or a human) swim intensively for three hours a day, five days a week, yeah, there is going to be oxidative stress and hormonal dysfunction. (As a side note in this study, the researchers noted the free radical damage could be protected with vitamin E.)
But this doesn’t mean aerobic cardio is bad. Swimming intensely for three hours (gotta be a long time for a rat) is going to tax the anaerobic system pretty significantly. This is not aerobic—it’s chronic anaerobic cardio. When you’re constantly using your anaerobic system more than your aerobic system, it puts a major stress on your entire body: your nervous system, cardiovascular system, hormonal system, immune system, and digestive system—pretty much all of it. For example, if you’re out for a long run, say 30–60 minutes, and your aerobic system is very poor, then you might be running at 70% anaerobic and 30% aerobic. But if you develop your aerobic system, then at that same pace you could flip the energy utilization to 70% aerobic, 30% anaerobic. You’re a much more efficient athlete. This is evident when using a heart rate monitor: You can see your heart rate is lower at a given pace/exertion level than the previous weeks or months. If you have access to an exercise physiology lab and a gas analyzer, you can measure your respiratory quotient—the level of aerobic (fat burning) versus anaerobic (sugar burning)—occurring during your run or other workout.
Anaerobic Conditioning: Are You Ready? Probably Not
Type II fast-twitch muscle fibers are primarily anaerobic (some are a mix of both fast- and slow-twitch); they burn sugar and creatine phosphate and are more for power and speed. They’ll increase your mitochondria too, but the anaerobic system will fatigue much faster than the aerobic system. High-intensity workouts tend to be predominately anaerobic, as is much of strength training, due to various type II muscle fibers being utilized and developed rather than type I aerobic fibers. However, this is a generalization, as some forms of strength training can also develop the aerobic system. Anaerobic activity incurs oxygen debt and a build-up of lactic acid; muscle imbalances and fatigue can result if continued. Muscle imbalances can be verified through certain manual muscle-testing evaluations (it’s a very accurate neurological assessment when performed correctly) and visual inspection—one hip higher than the other or one shoulder rotated inward, for example. Pain, poor performance, and injury often result from chronic muscle imbalances.
Essentially, you’re almost always using both systems (the exception would be an all-out sprint), depending on several factors that will be discussed later: exercise, diet, and lifestyle (overall stress levels). Anaerobic endurance and strength are essential in many circumstances and sports, but it is the aerobic system that will provide you with the endurance to work, play, think, sleep, and go several hours without food. Oh yeah, and without a healthy aerobic system, you won’t be a star in the sack—impotence and premature ejaculation for men and a lack of sex drive and the inability to achieve an orgasm for both sexes are partly dependent on a healthy aerobic system (among many other factors).
True Aerobic Training
The line between predominantly aerobic and predominantly anaerobic is determined by your lactate threshold (LT). Below the LT, you will be more aerobic than anaerobic, and above you will be more anaerobic than aerobic. True aerobic training is focused around lower-effort training zones 2 and 3, not the typical 3+ zone most are training their chronic “cardio” in. The “180-Age Formula” is also a great way to determine your aerobic training zone. Finding your heart rate zone is discussed more in Part II. Training around your LT too often is not a wise idea. Some call this area the “red line” or “black hole”—it’s a great way to overtrain and should be left for hard days (hard group rides/runs) or racing days. A conditioned athlete may be able to endure this rate of exertion for well over one hour, whereas an unconditioned, weekend warrior may be lucky to withstand 15 minutes. Therefore, anaerobic training is often best performed as shorter, hard interval training above your lactic threshold, well into the anaerobic realm of training. This is where high-intensity interval training (HIIT) has its place. This will be discussed next in Part II, along with developing your aerobic system regardless of your sport or goals.
Sock Doc Training Part II: Build Your Aerobic System: Move Your Ass Often, but Not Too Quickly