We have learned that in general, the higher the amount of reps, the more slow twitch fibers you work and the lower the amount of reps, the more fast twitch fibers you work. You also learned that sets in the 1-5 rep range do not recruit as many fast twitch fibers as sets in the 6-12 rep range, although they do recruit a higher percentage of fast twitch fibers compared to slow twitch. Low rep sets can be used to your advantage to work through a plateau or gain strength while maintaining the same size.

Low repetition work (in the 1-5 rep range) provides an extremely unique adaptation. To overcome the weight, your body must recruit as many motor units as possible. This will cause your nervous system to become more efficient at this process. Over time, you will learn to lift the heavier weight with all (or close to as possible) of your motor units in one rep. Powerlifters are extremely strong for this reason. They can make all the their motor units fire at once!

Even the smaller muscle groups have over 100,000 muscle fibers. A motor neuron is what stimulates our muscles to contract. It carries impulses (messages) from our brain and spinal cord to our muscles. One motor neuron controls anywhere from 2-2,000 muscle fibers. A single motor neuron and the fibers it stimulates are called motor units. Each motor unit fires with a frequency that is conducive to the fibers it stimulates. Simply put, a slow twitch motor neuron will cause the muscles in it to contract SLOWLY while a fast twitch unit will fire QUICKLY.

The quicker the motor neuron fires, the more power it produces! If the activity is light, it will stimulate mostly type I muscle fibers. When it becomes too intense it will call upon type IIa muscle fibers. And finally, for the highest intensity movements, our muscles will recruit the type IIb fibers. This is why type I fibers are called low threshold, and fast type IIb fibers are called high threshold. Low threshold means they are the first muscle fibers to be recruited and high threshold because they are only recruited under the most intense circumstances. Our bodies always activate muscle fibers in this fashion.

 

 

There are two different types of muscle fibers.  We all have slow twitch (Type I) muscle fibers and fast twitch (Type II) muscle fibers. We can further categorize fast twitch muscle fiber into Type IIa and Type IIb. There are even Type IIbx, which I won't get into in this article.

TYPE I MUSCLE FIBERS SLOW-TWITCH-Type I muscle fibers have the slowest-contractile speed, the smallest cross-sectional area, the highest oxidative (aerobic or endurance) capacity, and the lowest glycolytic (anaerobic or power) capacity. They contract slowly and are able to hold a steady paced twitch for long durations without fatigue. Type I muscle fibers are predominately used in endurance activities. Long distance runners, swimmers, and cyclists mostly use Type I fibers.

TYPE II MUSCLE FIBERS FAST-TWITCH-Type IIb muscle fibers have the fastest-contractile speed, the largest cross-sectional area, the lowest oxidative capacity, and the highest glycolytic capacity. They are ideally suited for short, fast bursts of power. These muscle fibers are used in such activities as sprinting or powerlifting. Type IIa muscle fibers are intermediate and their properties lie between type I and type IIb.

HOW TYPE I & TYPE II FIBERS ARE DIFFERENT
Type I fibers are different than type IIb fibers for many reasons. We can think of them as opposites. Type I fibers are recruited in long, endurance activities, while type IIb are recruited for short, fast bursts. Type I fibers are highly oxidative and are not likely to hypertrophy (increase in size) as much. Type IIb fibers are highly gycolytic and tend to hypertrophy more than type I fibers. Type I fibers are also known as red fibers due to their abundant supply of blood. Type IIb fibers have little blood causing them to be white in appearance.

Fats are very important, as we need them in achieving optimal health.  However, we do not need a lot of fat.  Most Americans get about 30-50% of their daily calories from fat.  This is why we have the greatest development of heart disease, stroke, diabetes, hypertension and obesity in the U.S.  It is from our high saturated fat intake.  We only need 10% of our daily calories to come from fat.  It is not hard to do.  First, you must choose leaner proteins such as chicken breast and turkey breast rather than beef and pork.  Secondly, do not grease or deep fry your food and smother them in butter and cream sauces.  It is as simple as that!  If you adhere to the above, it will come out to 10% or less fat each time.

You have probably heard of the good fat/bad fat controversy.  Bad fats refer to all of the saturated fat (animal fats).  These are unhealthy because, not only will they make you fat, but this type of fat will get into your arteries, clog them up and possibly give you a heart attack or stroke at the age of 50.  The good fats refer to oils, which are unsaturated.  These will not get into your arteries and give you a heart attack but they could collect on your stomach or on your thighs if you eat too much of them.

It is important to reduce your fat intake at this point in your program, because we are trying to reduce your fat stores.  It is not possible to reduce the amount of fat cells you have, but it is possible to reduce the size of the fat cells.  When you eat fat, your body breaks it down as a triglyceride and sends it out into the bloodstream.  That triglyceride will circulate around the bloodstream and become available for extra energy, if your body requires it.  At the end of the day, if your body did not use it for energy, it will attach to a fat cell and become more stored energy.  The problem is this:  when your body starts looking for extra energy, we want it to come from your fat stores rather than the fat that you keep putting in your mouth.  The only way we can change your body composition is to reduce those fat stores.

Carbohydrates are just different forms of sugars.  Carbohydrates fuel your body.  As you must put fuel into your car for it to run, you must put carbohydrates into yourbody for itto perform.  Carbohydrates give you energy to lift weights and run on the treadmill.  There are two major types of carbs.  There are simple carbs and complex carbs.  This refers to the size of the sugar molecule.  Simple carbs are small sugar molecules.  Because they are so small, they are broken down and sent out into the bloodstream rather quickly.  Simple carbs include foods such as table sugar, candy, syrup, and honey.  Complex carbs are larger molecules and since they are bigger, they take longer to break down.  Therefore, they are released gradually into the bloodstream.  Complex carbs include foods such as grains, beans, oats, rice, corn, wheat, pastas, brads, potatoes, and yams.  Fibrous carbs have minimal quantity calories but are high in fiber helps increase metabolism.

Macronutrients are another name for proteins, carbohydrates, and fats.  These are all important and responsible for specific functions in the body.  You need to understand what each nutrient does so that you can apply them in the right quantities for maximum results!  Diet is at least 85% of the whole picture.