Muscle tissue is a contractive type of tissue that can undergo tension by shortening (concentric contractions), lengthening (eccentric contractions) or remaining the same length (isometric contractions).
An example of a concentric contraction is performing the first part of a biceps curl where you hold a dumbbell down in one hand down by your side and then flex your elbow upward. The bicep muscle shortens in the process while undergoing tension. See the figures below:
An example of an eccentric contraction is performing the second part of the biceps curl, where you slowly lower your hand back down to your side. The bicep muscle is still undergoing tension only this time it is lengthening. The same figures are shown below, just in reverse order.
An example of an isometric contraction is holding a bicep curl at a halfway point, or one where your forearm is parallel to the ground, for about 10 seconds. The length of the bicep muscle remains the same during this time period, however, it is still undergoing tension.
The cells that make up your muscle tissue consist of the proteins actin and myosin. Each of these proteins is arranged into very fine threadlike filaments within the cell.
Myosin is a rather thick and active protein and is considered a molecular motor protein that is able to ratchet along the surface of a suitable substrate (actin). With each “turn of the ratchet”, they are able to grab the substrate and pull themselves in a given direction. Thus they are able to convert chemical energy into mechanical work. This is their main function.
Actin is a rather thin and passive protein when compared to myosin and has several functions within the cell. One of these functions is to give mechanical support to the cells and another is to allow for cell motility. With regards to muscle contraction or tension, actin serves as the substrate on which myosin proteins ratchet their force.
The basic unit of arrangement for the actin and myosin filaments within the cell is called a sarcomere. A sarcomere is arranged with the thick myosin filaments bordered by two actin filaments. See Figure 4.
The ends of each thick myosin filament grab the adjacent thin actin filaments repeatedly, ratcheting and then letting go; the actin filaments are pulled closer together in the process and the sarcomere shortens during a concentric contraction.
During an eccentric contraction, or one where the muscle lengthens while undergoing tension, this myosin filament detach from their actin filaments.
During an isometric contraction the myosin filaments hold firmly to the actin filaments without any movement.
There are three different types of muscles: 1) cardiac muscle, 2) smooth muscle and 3) skeletal muscle.
Cardiac muscle is an involuntary muscle type found only in the heart. It has striated fibers with its sarcomeres packed into extremely organized groups. This type of muscle relaxes and contracts in intense short bursts. You are probably well aware of this fact, especially after completing exercises such as running where you can feel the pounding of your heart through your chest.
Smooth muscle is also an involuntary type of muscle found inside the walls of the organs of your body. Your intestines, blood vessels, stomach are a few of the structures in your body lined with smooth muscle fibers. Like cardiac muscle, smooth muscle is also under unconscious control.
Skeletal muscle is the only voluntary muscle of the three. These muscles attach to the bones of your body through a highly elastic tissue know as tendons. They are located throughout your arm, legs, and torso and provide for movements of your body such as walking and running, as well as less visible movements such as maintaining an erect posture.
Skeletal muscle is the type that all athletes seek to directly improve through various types of exercise. This is naturally due to the fact that these muscles are under your conscious control.
Skeletal muscle consists of two main fiber types:
Type I fibers and Type II fibers.
The Type II fibers are further subdivided into two groups: 1) Type IIa and 2) Type IIb
Type I, Slow twitch Fibers.
They are called slow twitch fibers because when compared to the Type II fibers, they are slower to contract. Some studies suggest that their contraction rate is two to three times slower than Type II fibers.
The slow twitch fibers are found throughout your body but they are in higher concentrations along the postural muscles of your spine. They are highly resistant to fatigue. This allows them to maintain your posture, both sitting and standing for hours at a time before you feel any tiredness or soreness in them.
They have the ability to withstand fatigue because they contain large and numerous energy producing mitochondria when compared to Type II fibers plus they also contain high levels of myoglobin that gives them a dark reddish color. In laymen’s terms, slow twitch fibers are known as “dark meat”
Other characteristics of Type I fibers are their large number of capillaries per cross section and their ability to generate ATP aerobically. Athletes who are born with a higher percentage of slow twitch fibers in their body tend to excel in events where endurance is required, such as in running a marathon.
Type IIa, Fast Twitch Fibers. These are called fast twitch fibers because when compared to Type I fibers, they are considerably faster to contract, however, they don’t contract as fast as the Type II b fibers, which are the fastest of them all.
Type IIa fibers are similar to Type I fibers in that they also contain high level of mitochondria. This makes them moderately resistance to fatigue.
Their capillary density is relatively high, although not as high as Type I fibers, but still it is considerably higher than Type IIb fibers. This along with an equally high concentration of myoglobin as the Type I fibers gives them a reddish color as well.
These fiber types are also found throughout the body but are predominantly located in the extremities. Generally speaking, the amount of force a Type IIa fiber can produce is typically greater than Type I but less than Type IIb, but this also depends upon the situation you find yourself in since all muscles are capable of extremely strong contractions given the right circumstances.
An example of how all of your muscles can contract very strongly is when you are playing a contact sport such as football and are getting prepared to take a hit from a defender. Slow twitch muscles along your spine clamp down on your vertebrae to prevent injury just as hard as the fast twitch fibers in your extremities. However, since there is no real lever where these slow twitch fibers are attached to measure their force, they are often mistakenly considered weaker in comparison.
Athletes who are born with a higher concentration of Type IIa fibers tend to excel in your middle distance track events such as the mile and ½ mile as well as team sports such as basketball and soccer.
Type IIb, Fast Twitch Fibers. These are the fastest fibers types in the body. They are located predominantly in the arms and legs. Their ability to contract fast along with their location in the body enables them to generate very powerful contractions over a short period of time.
The downside to this is they fatigue very easily. One can maybe sustain an activity such as sprinting at a high rate for only 20-30 seconds before their speed begins to drop off.
This is due to their low myoglobin content, lowered numbers of energy producing mitochondria when compared to Type I fibers, and lowered density of capillaries per cross section. These characteristics also give them a pale colored and in laymen’s terms, this fiber type is referred to as light or "white meat".
Most of the exercises people find themselves in the gym or out on a track or field involve routines that put their muscles through concentric contractions (muscle tension during shortening) or eccentric contractions (muscle tension during lengthening).
Exercises in the gym that fit these descriptions are most of your dumbbell exercises such as bicep curls, shoulder presses, and chest presses along with other routines such as rows, squats and leg extensions.
Exercises away from the gym would include most of your running sports or drills along with any jumping routines such as those done during plyometric box jumps or perhaps the field events such as the long jump and high jump.
All of these exercises and more have value to an athlete. No training routine would be complete without at least involving some of them.
So what effect do the many commonly performed exercises have on your body and in particular, on your muscles?
The primary goal of most exercises is to build strength within the muscle. If workouts are performed for say 30 minutes or more, endurance within your muscles and body also increase with those specific exercises or movements.
How then does this occur?
When muscles undergo tension, either by contracting or lengthening, the resultant effect on the muscle is first to open up the blood supply to these muscles providing them with the much needed oxygen and nutrients.
Repetitively performing exercises on your muscles will ultimately stimulate growth in the cells known as hypertrophy, which means, to get bigger.
Hyperplasia, another term used to define a change in an organ or tissue, is a general term referring to the proliferation of cells beyond that which is normally seen, such as in the case of a tumor. Hyperplasia doesn’t occur with exercise.
When muscles hypertrophy, the most common physiological changes that take place within the muscle are an increased number of mitochondria formation and an increased number of capillary formation per cross section. The mitochondria are the energy storehouses of the cells and it stands to reason that when you get stronger in doing a certain exercise, the mitochondria would naturally have to increase to accommodate this change.
Likewise, with the increase in size of the muscles cells, more and more oxygen and nutrients will be required to support this new development and the capillaries, which are responsible for transmitting them, would naturally have to increase to service the cell.
These two main changes, increased numbers of mitochondria and increased numbers of capillary formation, are common with increasing muscle size.
Is that a good thing? Sure it is.
Larger muscles always look more attractive on an individual than smaller ones and muscular strength typically adds to your confidence as well as to the much desired athletic performance.
With all positive changes however, there’s always the potential for negative ones to go along with them.
In the example above, regarding the physiological changes in the mitochondria and capillaries, you may remember that high numbers of these two found within a cell are characteristics of Type I fibers, or slow twitch fibers. Type IIb fibers, fast twitch fibers, typically have lower numbers of them.
Does that mean that when your muscles get big that your fast twitch fibers are changing to slow twitch fibers? No.
As of the writing of this article, this has not been proven. However what has been proven is that by overdeveloping your muscles, especially the ones containing high amounts of Type IIb fast twitch fibers, you create within the fast twitch fibers characteristics of slow twitch fibers.
As a result the fast twitch fibers in these muscles begin to behave a little more like slow fibers and may not perform up to their potential for fast contractions.
If, when you exercise, your goal is to build strength and endurance, then this wouldn’t be seen as a problem. However if, when you exercise, your goal is to build speed and quickness, then you might find yourself struggling against the very laws of nature that prevent you from achieving this goal.
With all things there needs to be a proper balance for everything, including your athletic performance, to work at maximum efficiency. Performing concentric and eccentric exercises are necessary and needed to form a solid strength foundation in which to develop your athletic skills.
Sometimes these types of exercises translate into your being able to get faster and perform with greater endurance. Other times however, your strength and endurance improve, but your speed ends up dropping.
We haven’t mentioned too much about isometric training yet, but now is the time. Isometric training, where the resistance band is used instead of weights for the resistance aid, is a unique training strategy that enables your muscles to get stronger and faster with very little or no hypertrophy, providing that you don’t engage in this activity for longer than 15 or 20 minutes a day.
Figure 6. Example of an isometric contraction using the resistance band.
Unlike weights, the resistance band offers hyper-elastic resistance forces that change the amount of tension being supplied back into your muscles with even the slightest of movements. You can learn more about how the bands with isometrics increases your speed here. (Resistance Bands For Speed Training).
Since your muscles typically won’t hypertrophy with this technique, the strength and coordination you develop within your muscles won’t be offset by any additional body weight that is quite common with most other strenuous exercise routines.
By limiting the training time to a few minutes the Type IIb fast twitch fibers are conditioned for their natural ability to contract quickly.
Including isometric training exercises with the resistance band into your current training routine will complete the three different types of muscle contractions your body needs to excel:
1) isometric contractions
2) concentric contractions and
3) eccentric contractions.
The results will be seen in more complete development of your athletic skills and improved overall athletic performance. Whether you are trying to make the team, get off the bench, standout from the crowd, or advance your athletic career - adding isometrics with the resistance band to your workout routine for increased muscle speed may by your key to success.
Read what others just like you have had to say regarding this remarkable training strategy. (AthleticQuickness Reviews & Testimonials)
Dr. Larry Van Such