Anatomy and Physiology

I'm sure many of you don't really care too much about anatomy and physiology, heck, lot's of my readers probably don't even make it this far! But if you have, good for you, you won't regret it!

You can learn a lot from magazines and people around you, but usually you only learn 'what', and not 'why'. On this page I hope to give you enough information so that you could possibly answer some of the 'why' questions yourself.

Hopefully you will gain an understanding of how the body works, and in turn, understand how and why or certain supplements, training techniques and diets do and don't work. It let's you make more educated decisions when designing a program or choosing the foods you eat, and maybe gives you some good material when you get into a debate with someone who thinks they've got ALL the answers.

Which leads me to another very important point I'd like to mention before moving on. There are no absolute truths in bodybuilding! Some things may work for some but not others. Our understanding of how the body functions continues to grow, so we must keep an open mind to new ideas.

One classic example is the low-fat diet craze that has prevailed over the last decade or more. Obviously it's not working, so forget about it! More recently, bodybuilders' concept of simple vs. complex carbs has been shattered by the glycemic index, yet some bodybuilding magazines still make reference to it!

I am no expert, and I don't claim to 'know' everything or even anything. I can only convey to you what I have read, what I believe, and what my interpretations are (and I have many!). I do a lot of reading, and try to keep myself up to date as much as possible, so some of the things I say may seem absurd, because they haven't been commonly accepted yet. But I don't fabricate my information. I get it from reliable sources, and pass it on to you!

Muscle

This is of course of primary interest to anybody trying to build a better body! And it serves us in this quest in a couple of ways: to lift weights and get big, and to do cardio and burn fat. It is commonly known that aerobic exercise burns fat, and that glucose (from broken down glycogen)is a large supplier of energy, but do you know what role creatine plays? Let's find out.

Here is a large diagram of most of the superficial muscles of the human body.

Energy systems of muscle

During any activity, basically all energy system's get called into play to some degree, though some to a greater extent than others. I list them here in order from quickest, and activated most during high intensity (like creatine), to slowest and lowest intensity, like fat burning.

ATP - Adenosine tri-phosphate

This is THE primary source of energy for muscle contraction. All other 'energy sources' actually just generate more ATP as it gets used up. The energy is derived from removing a phosphate ion from ATP, resulting in ADP (Adenosine di-phosphate). All the other energy systems function in re-attaching a phosphate ion to ADP to form more ATP for use.

Phosphocreatine system

This is the very first energy system that comes into play, immediately! It is very fast, and can supply more ATP for more muscular contractions in milliseconds, which is crucial when doing high intensity workouts.

Supplementing with creatine boosts your body's stores of this important substance, which is why you can lift heavier and longer. It comes into play mostly during very intense workloads as the other systems are too slow to provide the needed energy. Another reason this lets you workout harder and longer is because unlike deriving energy from glucose, this system doesn't result in lactic acid buildup.

Glycolytic system

This system kicks in when creatine system is depleted, or rate of energy used is faster than the phosphocreatine system can supply it. It is the breakdown of glycogen into glucose into pyruvic acid, which then enters the Krebs cycle, that provides the energy for restructuring ATP.

During weight training, this is the primary energy source, which is why carb-loading can lead to some fantastic workouts, and why workouts are sluggish while dieting. It is known as the anaerobic system, as no oxygen is immediately necessary for energy production. The waste product is lactic acid, which decreases the ph of the muscle, and leads to muscular fatigue (chemical reactions are less efficient in acidic environment).

Oxidative system

This system comes into play during very low intensity work, such as light cycling or jogging, and is what we must tap into if we want to lose fat. It is also the primary system used during rest. It can use the end-product of the glycolytic system(pyruvic acid), fats, and amino acids.

In order to use this system during exercise to burn fat, it is important that your muscles get sufficient oxygen. If your intensity level gets too high, your body must resort to anaerobic systems, and you stop burning fat. If you experience lactic acid buildup, your are training with too much intensity.

Fast-twitch and Slow-twitch fibers

Muscles consist of mainly these two fiber types, on average in a ratio close to 1:1. However, there are differences between individual muscles, as well as individual people. Some people have more of one fiber type than the other, and this is primarily dictated by genetics. I have read that very specific training may change the ratio slightly, though the effect would probably be negligible. For maximum growth, vary repetition ranges to target both fibers.

Fast-twitch

grow in size more than slow-twitch when trained
activated more in explosive movements (lower reps)
rely more on stored energy (anaerobic metabolism)
Typically found in higher concentrations in hamstrings, abdominals, and gastrocnemius(heart shaped calf muscle)

Slow-twitch

doesn't increase as much in size when pushed to the limit
used more in endurance activity like jogging, cycling (not sprinting)
rely on aerobic sources of energy such as oxidation of fat
typically found in higher concentrations in soleus (calf muscle next to bone) and maybe the forearms?

Muscle cells, chemicals, and number

The number if muscle cells in your body is pretty much fixed by the age of 20, much like fat cells. They can only grow bigger, but chances of new ones forming are slim. Is it impossible? Probably not. One thing I read said that 'once already present muscle cells become full of actin and myosin muscle fibers, the body will make new muscle cells.' I know of no studies that support the existence of formation of new musle fibers (hyperplasia).

Rather than go into the very nitty griity, check out this page of very extensive muscle coverage: The Building Bodies Page which alsop happens to be a great all around web page! (BUT ALAS IS NO MORE! LET ME KNOW IF YOU FIND THIS PAGE ELSEWHERE, THANKS)

Metabolism

I personally find this section more important than that on muscle, because as long as you train regularly and put some effort into it, your muscle will become stimulated to grow. There aren't that many different ways to train a muscle, but there are many different alterations you can make to your diet to fine tune your performance.

The most important items covered here are the hormones insulin and glucagon, and how they affect energy use, uptake, and storage. I'll try and put this information into a big-picture type of format.

When you eat carbohydrates, they are absorbed as either glucose, lactose, maltose, fructose or glycogen. The body can only use glucose, so all others are further broken down by enzymes into glucose (and glycogen which is stored as such in the liver and muscle). So depending on what foods you eat, and how much, your blood glucose levels go up. This triggers the pancreas to release insulin into the blood, which functions in bringing blood glucose levels back down to an amount that the body always tries to maintain.

It does this in several ways:

it shuttles glucose to be stored in muscle cells as glycogen
it stores glucose in the liver in the form of glycogen
if muscles and liver are full, it converts remaining glucose into fatty acids

Increased insulin sensitivity allows more glucose to be stuffed into muscle cells, preventing conversion of excess glucose into fatty acids. Insulin sensitivity can be increased by depleting the muscle of glycogen like during a workout or (to a lesser extent)after a night of fasting, or by means of supplementation with chromium and vitamin E (both are minimally effective if at all).

Eating too many carbs over a long period of time actually reduces insulin sensitivity and can in fact lead to diabetes, which is why a larger percentage of North Americans are overweight, and are being diagnosed with diabetes. This decrease in insulin sensitivity leads to a vicious circle: the more you eat, the more insulin resistant you become, and the more weight you gain.

Insulin also functions as storing fatty acids in adipose (fat) tissue, which we definitely don't want. Fat is absolutely necessary for sustaining life, and it is used in many bodily functions. The fats we eat are also digested and absorbed as fatty acids, and some are used up in forming cell membranes, hormones, etc. And just like excess glucose is converted into fatty acids and stored in fat cells, so are excess dietary fatty acids.

But don't think that cutting fat from your diet is ok since excess carbs will still be converted into fat, because there are two essential fatty acids which the body needs but cannot synthesize itself: linoleic and linolenic fatty acids. A deficiency in either of these can cause serious health problems. More about that in the nutrition pages!

The other hormone that 'competes' with insulin is glucagon. Whereas insulin functions in storing glucose and fatty acids, glucagon's role is the opposite: breaking fat down for energy. This is exactly what we want when we are trying to burn fat.

Something important to keep in mind is that glucagon does not function in the presence of insulin. After all, why would the body try to break down fat for energy when there is plenty of glucose in the blood? The trick is to do your fat burning exercise when there is no insulin in your blood, as in long after a meal, or after a meal which releases little or no insulin, or best of all, first thing in the morning.

You may have heard that exercise increases your metabolism. Well, I just read an interesting article that compared untrained individuals with trained individuals. Both mobilized roughly the same amount of body fat for utilization, but the trained individuals were able to clear the fatty acids out of the blood faster. Untrained individuals burned less, and after excercising, the excess that didn't get used up would be stored away again.

So as you can see, yes, training does increase your metabolism by increasing your ability to burn fat. And the best way to take advantage of this is to combine cardio with weight training to both increase your ability to use fat, and give your body the opportunity to do just that!

Hormones and Neurotransmitters

There are plenty of hormones in the human body that regulate all sorts of physical development and metabolic processes. I will discuss only those of primary interest to those trying to build a better body, anabolic (building) and catabolic(breaking down) hormones.

Testosterone, as you all know, is probably the most important hormone for building muscle. It works by increasing muscle protein synthesis by binding to cell receptor sites which signals the DNA to signal the ribosomes to produce more proteins in the form of enzymes or contractile proteins (thanks to Chris for the details). Testosterone is regulated by several other hormones which I will discuss later.

Insulin is primarily involved in nutrient transport. It facilitates glucose and amino acid transport into muscle cells, and fatty acid transport into fat cells. It also blocks many catabolic processes which is a good thing. Insulin is released in response to food ingestion in an effort to maintain a baseline blood glucose level.

Let me get into more detail about how insulin works, and what it all does. The following is a chart taken from the book 'Protein Power' that compares the relative amounts of insulin and glucagon released in response to various combinations of food:

combination	insulin	glucagon
carbs alone	*****	none
protein alone	**	**
fat alone	none	none
protein + fat	**	**
carbs + fat	****	none
low carb + high protein	**	*
high carb + low protein	*********	*

Insulin's role is not only shuttling nutrients into tissues, but also fat storage, triggering cholesterol synthesis, water and sodium retention, and possibly appetite control (albeit indirectly). It also works against glucagon, preventing fatty acid mobilization, and may also prevent the release of growth hormone, if present in high levels.

Growth hormone is another big anabolic hormone, and a lot of research is currently underway to try and boost growth hormone in humans. Some doctors can prescribe growth hormone, though this is rare and may not be of great benefit to bodybuilders. Currently, a lot of supplement manufacturers are also jumping on the bandwagon, coming out with all sorts of growth hormone boosters. Whether they work or not remains to be seen.

Among some of the emerging supplements to boost GH are Glutamine (2-3 grams before bed), Calorad (advertised as a fat burner, take 10(?) grams before bed, 3 hours after eating), and GHRP (Growth Hormone Releasing Peptides advocated by Muscle Media). Heavy exercise also stimulates GH release, and supposedly avoiding high-glycemic index foods immediately after a workout also increases GH release.

Growth Hormone is produced in the hypothalamus, and is metabolized into a host of other hormones in the liver. GH is the primary hormone responsible for stimulating tissue repair, cell replacement, brain function and enzyme production. It acts on nearly ever tissue in the body. GH levels rise and fall often and quickly, reaching peak levels after strenuous exercise and during deep sleep. It also facilitates more complete amino acid transport into cells than insulin (all 20 aminos) which is crucial for protein synthesis. (Another tidbit from Chris)

Here is an exerpt from ValueNutrition that discusses GH function:

Everything from the concentrations of nutrients, electrolytes, water and hormones in the bloodstream to emotions, stress and trauma, impacts the hormonal system through the hypothalamus. The hypothalamus then uses neural stimulation of the anterior pituitary gland to control growth hormone (GH) release. Unlike other hormones (with the exception of the thyroid) GH affects almost all body tissues.

GH is considered a master hormone, which controls many organ and body functions. GH also regulates itself. The rejuvenating effects of GH are all encompassing, acting on both the mind and body. GH is the primary hormone responsible for stimulating tissue repair, cell replacement, brain function and enzyme production.

GH is the ultimate anti-aging therapy and effects almost every cell in the body, rejuvenating the skin and bones, regenerating the heart, liver, lungs and kidneys, bringing back organ and tissue function to more youthful levels. GH revitalizes the immune system, lowers the risk factors of heart attack and stroke, improves oxygen uptake and helps prevent osteoporosis. It is a powerful anti-obesity hormone and acts to naturally enhance sexual function. For many it acts like a natural cosmetic, restoring skin elasticity, smoothing wrinkles and rejuvenating hair and nails.

The rate of GH secretion can rise or fall within minutes, with the highest levels, occurring after strenuous exercise and during deep sleep. Most other changes are usually related to the concentration of nutrients in the blood: (protein, fat and sugar) The release of growth hormone, is also affected by stress, excitement and trauma.

Cortisol is the primary catabolic hormone. It's levels are highest early in the morning and during periods of high stress, and lowest in early stages of deep sleep. Cortisol functions in reducing cellular synthesis, and mobilizing amino acids from muscle tissue to undergo gluconeogenesis in the liver (conversion to glucose). It halts growth and causes muscle breakdown.

But, cortisol also funtions in fat mobilization, which is probably why doing cardio first thing in the morning can be a more effective way to burn fat.

The control of cortisol is the bodybuilders best bet towards maximizing muscle growth. Insulin nullifies the effects of cortisol in all but the most stressful times, so eating food first thing in the morning and right after a grueling workout are critical to stop muscle loss.

Glutamine supplementation may aid in reducing catabolism in two ways: cortisol gets glutamine from muscle tissue, but if it's already present in the blood, may spare muscle, and supplementation may stimulate more growth hormone release.

Vitamins, dietary fat, phosphatidylserine, and branched chain amino acids may all play a role in inhibiting cortisol action, though more research is definitely needed to fully understand how and to what extent.

Several testosterone boosters have also been popping up in the supplement industry lately, most notably:

DHEA - a naturally occurring hormonal precursor to testosterone. Natural levels don't start to drop off until the age of about 25, and don't crash till about 40. Early supplementation should be avoided as excess DHEA may be converted into DHT (causing balding, prostate enlargement, acne) and estrogen (causing gynecomastia, increased fat deposition under the skin and water retention).
Androstenedione - Another precursor, closer to testosterone, and can also be converted into estrogen in the liver. Oral doses have shown increases of 100-300 %, which last for about 3 hours. Continuous use may result in some of the side effects of steroid use.
Norandrostenedione - similar to above, this is actually a precursor to not-testosterone, may have less side effects, and may also be better for fat mobilization.
Tribestan - tribulus terrestris, a herbal supplement that has shown to boost luteinizing hormone by up to 72%, resulting in an increase of testosterone on the order of 40%. Has also been used to increase male fertility my increasing sperm count and mobility.
Saw Palmetto - commonly found in 'male' remedies for prostate enlargement. Prostate enlargement occurs due to excess DHT production. DHT production is blocked by Saw Palmetto, meaning your testosterone doesn't go down this biochemical path, hence, more testosterone.Indole-3-carbinol and chrysin have same effects.

If you were to go to a number of sites that sell these supplements, you'll see piles of testimonials on how great these supplements are, how they've gain 10 pounds in 2 weeks, etc. Unfortunately, most of these supplements are banned in Canada, so I don't have the opportunity to try them myselves, and I can't really make any recommendations.

If you're curious, try some for a month, keep the rest of your training variables the same, and you'll see if it works. The problem with most supplements is that people revamp their entire workout and nutritional program when they go on a new supplement, after all, you want to get your money's worth. But then the question is, did your change of nutrition and training bring the results, or the actual supplements?

Neurotransmitters

The neurotransmitters of greatest interest to bodybuilders are the excitatory neurotransmitters including: dopamine, norepinephrine, epinephrine, and acetylcholine. These all function to some extent in flexing muscle and mental focus.

A depletion of neurotransmitters can lead to fatigue, decreased performance, even depression. Lifting heavy weights tends to use up these important substances quicker than usual, making overtraining a constant threat.

A few supplements worth trying out to increase you neurotransmitter production include:

St. Johns Wort - Used in Europe for years to treat depression, the active ingredient hypericin increases the half-life of neurotransmitters.
Tyrosine - an amino acid that serves as a precursor to dopamine, norepinephrine, and epinephrine which play a role in muscle contraction, performance and mental focus.
DMAE/Choline - is a precursor to the neurotransmitter acetylcholine which is also important in muscular contractions, coordination and balance.

Last Modified:
February 10, 2000

Exercise is not without its risks and this or any other exercise program may result in injury. To reduce the risk of injury in your case, consult your doctor before beginning this exercise program. The advice presented is in no way intended as a substitute for medical counsulation. The developer of Muscle101.com disclaims any liability from and in connection with any information conveyed on this web page. As with any exercise program, if at any point during your workout you begin to feel faint, dizzy, or have physical discomfort, you should stop immediately and consult a physician.