I was intrigued by a recent ABC "Catalyst" program that showed Professor Geoffrey Spinks from the University of Wollongong making artificial muscle fibres using nothing but normal nylon fishing line, an electric drill and a heat gun.
I wondered how he got this idea, and how was it possible to make such a complex body structure from these everyday simple materials.
Professor Spinks was modelling skeletal muscles (those we voluntarily control to make us move). They can only pull on the bones when they contract; they can never push. What happens is that they come in pairs, so that if we want to lift our arm (for example), our brain sends messages to tell the bicep to contract and that pulls on the bones and our elbow bends. If we want to put our arm down, then other signals are sent to the tricep on the underside of our arm, and this muscle then contracts to pull our arm down, and the bicep on the top side relaxes. Neither muscle ever does any pushing.
What are muscles made of
Natural muscles in our body are made mostly of specialised structural proteins. Some of these proteins work like tiny motors, and others just provide structural strength. The working proteins are called actin and myosin, and they form very thin but long filaments (myofilaments - "myo" is an old Greek word meaning "muscle"). These are packed together into larger fibres called myofibrils, many of which in turn are packed into muscle fibres that we can see.
Depending on the function of the muscle, these are arranged in bigger and bigger bundles, each layer surrounded by tough outer membranes, under which are the necessary nerves and blood vessels. Woven in the fibre in one way or the other, depending on the nature of the muscle, are fibres of a tough protein called collagen (it also occurs as part of skin, hair and nails). The skeletal muscles are anchored to the bone by tough, rubbery tendons – also made from collagen. (In case you are confused, ligaments are similar in structure but they join bone to bone.)
The proteins called actin and myosin are arranged in alternate layers. The myosin "walks" along the actin molecule, pulling itself along with each "step". This action can also be likened to the stroke of a rowing machine. Two different representations can be seen at: accessexcellence.org; and en.wikibooks.org
How do muscles get strong?
We don't have to worry about eating any particular proteins to build our muscles. As long as we are eating a balanced diet with SOME protein and some carbohydrates and a little fat, the proportions don't really matter and the total amount of protein does not need to be large. Our digestive system breaks down nearly all our food and uses the small bits to manufacture ("synthesise") the exact products we need to build all of our wondrous body, including our muscles, at the exact time we need them.
Again like all our body structures and chemicals, our muscles are continually being broken down (catabolism) due to the aging of the cells that make them up; and new muscle cells and structures are then synthesised to replace them (anabolism). If we use our muscles a lot, then although they are broken down at a greater rate due to wear and tear, the body is also stimulated to manufacture even more muscle cells; but more importantly, each cell becomes bigger, gets a better blood supply and more mitochondria (which are the tiny structures that produce energy) and also becomes more efficient in its action.
In this way, for example, you will see a bigger, stronger muscle in your dominant arm if you are a tennis player or bowler. (This applies to any and muscle that you put under the stress of exercise or training).
Those muscles you do not use get weaker because, although the cells are broken down more slowly, fewer and fewer are actually made to replace them; and those that are there start to work inefficiently. This situation is called "muscular atrophy" and it happens for example if you stop practising your habitual sport, or if you are ill in bed for more than a few days, or if you continually sit too long instead of walking around at regular intervals.
How damaged muscles repair themselves
Have you noticed a conundrum here? You will only gain more muscle if you first stress that muscle to make it break down faster. Part of the biochemical mechanism is actually inflammation. This is the body trying to protect the damaged cells from further harm, and it is absolutely necessary to stimulate new muscle cells to grow. Unfortunately, if the damage is extreme, it can "over-react" and the new muscles may not line up with the original filaments. Gentle exercise and perhaps advice from a physiotherapist will help the new muscles grow in the correct orientation, and then returning to any training regime will make sure the muscle grows strong again.
The funny thing about muscle growth and muscle repair is that it doesn't occur until after you stop working out and rest, when the body heals the inflammation and muscle breakdown that occurred during exercise. If you are an athlete, you should listen to your coach about alternating periods of training and rest!
This also concurs with several Biblical passages, including Exodus 20 verses 9-10 (KJV) "Six days shalt though labour, and do all thy work. But the seventh day is the Sabbath day of the Lord thy God: in it thou shalt not do any work, thou, nor thy son, nor thy daughter, thy manservant, nor thy maidservant, nor thy cattle, nor thy stranger that is within thy gates."
A laboratory solution looking for problems
So, I wondered, how will Professor Spinks' nifty nylon muscle help people? The nylon certainly mimics the structure of the muscle, and it can be stretched and returns to its initial shape many times over (as demonstrated in the TV program). But it has no power supply – no blood vessels to bring glucose and oxygen, and no mitochondria to convert those things to energy.
It may be useful in those with muscle-wasting diseases, where their muscles just continue to atrophy and don't repair themselves; in those cases it could help them to retain some strength. It may be useful in cases of surgery where small amounts of muscles are damaged. Or it may be useful worn on the outside, for more comfortable and effective compression bandages for example.
Professor Spinks has also found that his nylon muscles will change with temperature – so he speculates that they could be useful woven into clothing that expands and opens up to a looser weave when we get hot, or in greenhouses where the nylon spirals could be levers to open and close vents automatically as the weather changes.
Or, as happened with the laser, common sticky-tape and post-it notes, the inventors may have no idea what problems others will solve with their nylon muscle "solution".
Dr Mark Tronson is a Baptist minister (retired) who served as the Australian cricket team chaplain for 17 years (2000 ret) and established Life After Cricket in 2001. He was recognised by the Olympic Ministry Medal in 2009 presented by Carl Lewis Olympian of the Century. He mentors young writers and has written 24 books, and enjoys writing. He is married to Delma, with four adult children and grand-children.
Mark Tronson's archive of articles can be viewed at http://www.pressserviceinternational.org/mark-tronson.html