What are muscles?

Without muscles you wouldn’t be able to do anything, not even speak or wink! But there’s much more to muscles than just giving your body the ability to move. In fact, there are three types of muscle in the human body:

• Skeletal muscle is what is attached to our bones to make them move. You might be able to feel the places where the muscles are attached to bones: the tendons. See if you can find the tendons at the back of your knee, or in your wrist. Where else do tendons occur in your body?
  
  
• Smooth muscle is involuntary, which means we have no control over it. Examples of this include the muscles that line the blood vessels, stomach, digestive tract and other internal organs. Imagine what it would be like if you always had to remember to make your stomach muscles move whenever you ate something.
  
  
• Cardiac muscle is the muscle that works the heart, which is also involuntary. It would be very difficult to have to remember to make your heart beat all of the time!

Did You Know ... ?

Muscles can be found virtually all over your body. This picture shows the skeletal muscle of the arm. Beneath the skin there is a layer of fat, and underneath this there is a membrane that holds the muscles together. You can see the muscles of the body in the Visible Human Project. This is footage of a real person who donated his body to science for research purposes.

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How do muscles work?

If you looked at muscle tissue closely, it is a lot like a system of telephone cables in bundles or fibres: each bundle contains smaller bundles of cables, each of which contain still smaller bundles.

Have a look at your upper arm, and particularly at your bicep. When your arm is straight, your bicep is long. Now bend your arm towards your body. The bicep gets much shorter – it contracts. You should actually see the muscle fibres go from being long and thin to being shorter and fatter. But how do the muscles return to their original length?

In her lecture, Dr Whiten tells us that a muscle can only be restored to its original length by applying another force. For every set of muscles in the body there is an equal and opposite set of muscles.

These 'opposite' muscles also allow us to control the way we lift and lower weights. Nerves play an important part in this process: they send impulses to the muscles to make them contract. In the thumb each nerve may activate up to one thousand cells, resulting in a single, very strong muscle contraction. If you’ve accidentally touched something very hot your muscles will have contracted very sharply.

Why do we need to exercise?

Even if you’re no Lennox Lewis, the human body has more muscle tissue than any other tissue found in the body. When muscle cells are exercised, they can double or treble in size.

Launch it ... Try to Pump Some Iron and see what happens with different sized weightlifters.
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Athletes may be tempted to use drugs to make them able to train and perform better in competitions, but this is dangerous and is also cheating. Scientists can detect drugs like Anabolic Steroids in the blood. But experts now say that the science of gene therapy (in which human DNA is added to the human body) may change sport forever.

There may be a price to pay for using genetically modified DNA though… the stress on the body’s joints and heart may lead to disease and other physical injury.

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