How many of you consider yourself a skeptic? I know I do. When an expert or authority makes a pronouncement that Cause A leads to Effect B, I’m a lot more likely to accept his or her ideas if this expert can explain how or why Cause A leads to Effect B or in some way describe the mechanism of its action. I have a hard time going on faith alone, especially since our playing field is littered with “experts”, many of whom disagree with each other. So when our experts tell us that aerobic exercise causes an increase in the amount of HDL cholesterol in our bloodstream, I would like to know how it happens.
Then, when a client, friend, or relative asks me to explain that benefit, I can confidently do so. Unfortunately, I have yet to read such an explanation from one of these experts, though I frequently read articles and texts claiming the above-described benefit accrue. I am often called to explain the benefits of the exercises that I recommend, as I am sure you are, so I researched this cause and effect relationship and here is what I found. I would like to share it with you so you can share it with others.
Before we look at the intricate relationships I’m about to describe, we have to make sure our listeners have the foundation necessary to understand the explanation. I ask them if they know what cholesterol is and make sure they understand that it is a waxy substance composed of fat and protein (hence the name lipoprotein) used by our bodies to build cell membranes and other cellular structures. They also need to know that our body constantly repairs, replaces, and constructs cells. I use the analogy of a construction site. Our body is like an intricate building that is constantly under renovation. Cholesterol is one of the construction materials. Because our body constantly uses this material, it manufactures its own cholesterol in the liver. In fact, 75% of the cholesterol found in the average healthy person was manufactured in the liver. The rest comes from the animal products we eat.
Now we know what cholesterol is and what it does. Next, we need to find out if our client/listener knows the two main types of cholesterol-LDL and HDL. I usually ask them if they can tell me what the initials stand for and for anything else they can tell me about them. They usually tell me on is good and one is bad and sometimes they even know which one is which! I make sure they know that LDL stands for Low Density Lipoprotein and HDL stands for High Density Lipoprotein and that they make up the two parts of the transport system to and from the cellular construction sites. The LDL leaves the liver bearing the construction materials and carries them in the bloodstream throughout the body. The cells use up part of the LDL during construction and leave the rest of the molecule as well as any unused LDL lying around the construction site like so much rubble. If you have ever seen a construction site, you know what I’m talking about. Although a beautiful thing is being built, small piles of debris surround it until the cleanup crew does its job. That’s where HDL comes in. As the other half of the transport system, HDL picks up the spent cholesterol, the rubble, and any disused LDL and takes it back to the liver where it can either be disposed of or be recycled into fresh construction material and sent out again. HDL is the cleanup crew!
We’ve made another important step in understanding and explaining this process. It is really hard to say that LDL cholesterol is “bad” cholesterol since we must have it to get the construction job done. It really only becomes bad when there isn’t enough HDL in the bloodstream to pick it up and take it back to the liver! Your client must understand this before the pronouncement cited in the first paragraph has any importance. Once he or she understands that our bodies constantly produce the cellular rubble of spent LDL and that the cholesterol we take in from animal products must also be kept in check, then he or she will understand the need to keep their HDL cholesterol at a healthy level. I believe clients should have a cholesterol screening as part of their initial fitness assessment. Cardiologists recommend that we focus on the ratio of Total Cholesterol to HDL as the diagnostic tool determining a healthy cholesterol mix. The ratio should be 5:1 or lower; a ratio of 8:1 is considered critically unhealthy. An unhealthy cholesterol ratio suggests a high risk for coronary artery disease, heart attack, and a shortened life span. Given that HDL cholesterol keeps the other types of cholesterol cleaned out of the bloodstream, we must maintain a healthy HDL level. We currently have two methods to do this-medical intervention with powerful cholesterol controlling drugs, or aerobic exercise. I believe drug therapy should always be the tool of last resort and aerobic exercise confers many other benefits besides boosting HDL levels (improving body composition not least among them!), so I recommend aerobic exercise to those that wish to regain or maintain a healthy cholesterol level. There are many acceptable forms of aerobic exercise and many of them are fun. Some people enjoy jogging, others swimming, others enjoy aerobic classes (I do), and as an NFPT trainer, I frequently recommend aerobic resistance training, especially to overweight clients that find these other modes taxing. Whatever the mode, the critical element remains unchanged-the exerciser must perform major muscle movements continuously for 20 to 60 minutes at sufficient intensity to keep their heart rate in the aerobic range, usually 60 to 80% of their age-adjusted maximum. And there lies the key.
We have now laid the foundation to look at what the experts have failed to explain. Aerobic exercise does, in fact, lead to an increase in an exerciser’s HDL cholesterol level if they engage in said exercise three to five times a week for at least 12 weeks with each session lasting at least twenty minutes in the aerobic range. How? Here we go all you skeptics. HDL’s job is to clean up the cholesterol debris from cellular destruction and construction. When we do aerobic exercise, we vigorously move large muscle groups for an extended period. Our muscles must use enzymes to effect these movements. Because aerobic exercise moves a lot of muscle for long periods, it uses a lot of them. In fact, every muscle movement, even one as simple as scratching my nose, requires these enzymes and our bodies give TOP priority to their replenishment. All enzymes are made from protein. As soon as we stop intense exercise, our bodies immediately initiate the replenishment of these enzymes. The first source of protein accessed by our bodies to build new enzymes is the very muscles that used them up! We call this process “catabolism” and we know that it is a natural phenomenon associated with exercise. Because aerobics moves so much muscle tissue at an elevated temperature for such a duration of time, it causes a substantial catabolic effect in these muscles. What is catabolism doing? It is breaking down muscle cells for protein and releasing substantial amounts of cholesterol rubble into the bloodstream. In our heightened, post-aerobic metabolic state this release signals the liver to produce more HDL for the cleanup crews. Our bodies’ adaptation to aerobic stress and the catabolism that accompanies it is to create more HDL to clean up the cellular mess that ensues. In the hours that follow the aerobic session, our bodies begin to reverse the process of catabolism and rebuild the muscles that were “sacrificed” to the enzymes. This, too, calls for additional HDL to keep the construction sites clean. It is through these mechanisms that our bodies react to aerobic exercise and boost the quantity of HDLs in our bloodstream.
The real beauty of this process, the real benefit, flows out of the fact that when the new HDLs have finished cleaning up the construction sites, they don’t just sit on their hands. They set about cleaning excess LDL from the bloodstream and lowering our total blood cholesterol. Some researchers state that the HDLs even begin to dissolve pre-existing plaque from the arterial walls once the blood cholesterol has been brought under control. Clearly then, any client with a family history of arteriosclerosis or a high cholesterol level needs to include aerobic exercise in their training program. These clients should always receive medical clearance to do so before they start. Once cleared, you can explain the tremendous benefit they will derive from this segment of their program. If they have an inquiring (skeptical) mind that needs the explanation of HOW aerobic exercise will “deliver the goods,” you are now armed with the means to satisfy their curiosity. How’s that for client service?
A healthy dose of skepticism keeps us from following unproven pronouncements made by “experts” that have something to sell. It can also inspire us to research valid pronouncements and discover the why and how of these truths and enable us to explain our recommendations to our clients. That impresses them. It is worth the time spent because it strengthens our reputations as trainers. If you would like to contact me with questions or comments, do so through this magazine or NFPT’s website. I look forward to hearing from you!