Muscle Fiber Types and Contraction

Muscles generate heat and force for movement, help us breathe, and keep our bodies upright. Skeletal muscle tissue is composed of two fibers, actin (thin fibers) and myosin (thick fibers). These two fibers give the muscle a striated appearance. In order for muscle to contract it must first be stimulated by nerves called motor neurons. A single motor neuron and the muscle fibers stimulated by it is called a motor unit. The recruiting motor units play a large part in the force of the muscle during contraction. The more motor units (muscle fibers) recruited, the stronger the force of contraction.

Muscle fibers are classified as Type I, Type IIa and Type IIb fibers. "Fast" and "slow" twitch are also two other classifications for muscle fibers. Type I fibers (slow twitch) fibers are more resistant to fatigue than Type IIa or IIb fibers and have a high capacity for aerobic metabolism, fatigue faster and are mainly anaerobic.

Slow twitch fibers are mainly for endurance while fast twitch are for speed and performance. A muscle will generally have an equal amount of both fast and slow twitch muscle fibers. In regards to hypertrophy (muscle growth), fast twitch fibers grow faster and larger than slow twitch. Within the fast twitch muscle fibers, type IIa fibers are considered intermediate between fast and slow twitch fibers in relation to speed and contraction. For example, Type IIa fibers can become more glycolytic or aerobic depending on the type of training an athlete performs. If an endurance runner were to stop running and start weight lifting, then his or her Type IIa fibers would become more glycolytic in order to handle the stress of the activity.

Muscle growth and endurance is an adaptation to stress. For example, a sprinter will develop large quadriceps and hamstrings in order to adapt to the stress, while an endurance runner will develop more endurance to efficiently handle the stress. Type I muscle fibers respond to stress by becoming more efficient and stronger with slight hypertrophy, rather than the extreme hypertrophy seen with Type IIa and IIb muscle fibers. This is the premise behind trainers recommending 6 reps for pure strength/muscle gain and why 10-15 reps are recommended to "tone" a muscle.

Finally, there are four different actions a muscle can perform; isometric, eccentric, concentric, and isotonic. An example of an isometric contraction would be pushing against a wall. Lifting a dumbbell during a bicep curl is considered the concentric portion while lowering of the weight is called the eccentric portion of the exercise. There are also called the positive and negative portions respectively. And finally, isotonic contractions are those that involve full body actions such as skating or running.

Find out more about Fitness at healthandfinesse.com

Hot Topics In Fitness

    Treadmll Ratings - What Most Buyers Don't Know About Treadmill Ratings

    If you're buying a treadmill, chances are you'll want to research before you buy. Everyone wants to get the best deal for a discount price. They also want to find the best treadmill to suit their work...

    Meditation Can Also Make Your Heart Happy

    Meditation is good for your heart. This is the message recently (in the year of 2006) conveyed by the Archives of Internal Medicine. The study reported that transcendental meditation (TM), a relaxatio...

    The History Of Tai Chi

    I've got something pretty miraculous to tell you about. I found out about this awesome way of balancing your mind and body. It is like nothing I have ever seen before. It's called Tai Chi and finding ...

    Tai Chi

    TaiChi is a complete and highly developed internal martial art (Neijia). A form of moving meditation, TaiChi promotes in the practitioner a sense of Qi (breath/life energy) circulation and health. As ...

    Is Home Exercise Equipment For You?

    We are bombarded with messages about the current obesity epidemic that seems to be under way and the need to combat it with daily exercise and a healthy, well-balanced diet. The FDA has even redesigne...

    Great Cardio Workouts You Can Do At Home

    You know how important cardio workouts are for your health and wellbeing, but it's hard to get a good cardio workout in when you can't leave to house to go to the gym or for a run. Here are some great...

    5 Tips To A Strong, Muscular Physique!

    For over ten years now, I have been a drug-free competitive bodybuilder, and I can tell you first hand what it takes to develop a muscular physique. In this article, I want to discuss with you my top ...

    Pulsating Tinnitus - Here's How To Beat It

    Throbbing Tinnitus - What Causes It?

    When you can hear a regular pulsing noise in your ears in tune with your your heart beat that is probably pulsatile tinnitus. There may be single or many rhythmi...

    The Top 5 Yoga Positions

    Often times the right information can change a person's life. This happened with me and yoga.

    There are a lot of yoga positions and poses that is built to enhance posture.

    All things consider...

    Why Weight Train During Pregnancy?

    There was once a time that a pregnant woman was thought of as "fragile". Any form of exercise was strictly prohibited by doctors and feared by concerned fathers. We've now come to realize that a pregn...

    3 Steps To Starting a Successful Fall Exercise Program

    Ah, the crisp cool breeze, the invigorating feel of the outdoors as the leaves start to turn colors, the sound of kids laughing on their way to school.

    Fall is the time for new beginnings. New...

    The Importance Of Creatine In Building Lean Muscle

    Creatine monohydrate can rightly lay claim to being the most popular and arguably most effective bodybuilding supplement currently available. The beauty of creatine is that it is 100% natural and occu...

Most Recent Fitness Supplements

Interesting Today:

Most Recent Fitness Blogs:

Releated to Fitness:

Fitness Links:

Fitness Fitness Rss feeds.