Alright guys, we need to talk about muscle. In previous articles, I have addressed what all muscles have in common – they all contract and they all have mitochondria. And I talked about Aerobic verses Anaerobic exercise and how the muscles can work with oxygen or without oxygen to create the energy they use to contract. Now I need to let you all know that you actually have 3 different types of skeletal muscle…
One body – Three types of muscle
If you striped all the skin from a person and just exposed the muscles you would see three different coloured fibers. It sounds super-gross but please try to imagine it: Red muscles, pink muscles, and white muscles. The red muscles are red because they contain lots of myoglobin: a protein that binds iron and oxygen. Your blood has a similar protein called hemoglobin which binds iron and oxygen. So when you see red, I want you to think about the globin molecule and an abundance of oxygen being present.
Red muscles also have lots of mitochondria. This too gives them a darker colour. And they also have lots of capillaries – these are small blood vessels which supply oxygen-filled blood to the muscle fibers. These red muscles are also known as “slow twitch fibers”. And guess what they do? They contract slowly for a long time without fatiguing. If you haven’t figured it out yet, these are the ‘Aerobic Muscles’ (ones you use during aerobic exercise). These are the muscles that use mostly oxygen to make their energy.
Now think about the white muscles. They don’t have as many mitochondria and the mitochondria they do have are smaller. They also don’t have as many capilaries. White muscles get most of their energy from sugar burning pathways (Google ‘Glycolytic Pathways’). These muscles are also known as ‘fast twitch fibers’. And guess what they do? They contract quickly, and with lots of force but can only do so for a short time before getting fatigued. And you guessed it, these are the ‘Anaerobic Fibers’ (the muscles used when doing anaerobic exercise). They don’t use much oxygen at all to create their energy.
So imagine what the pink ones are like. They are kind of in-between. They have mitochondria and capillaries but not as many as the red muscles and not as few as the white muscles. These muscles are also highly trainable. This means they will act more like Red Fibers if you do lots of exercise that encourages red fiber use (aerobic exercise). Or they will become more like white fibers if you do exercise that encourages more white fiber use (anaerobic exercise).
Your muscle types are unique! So train them…
Now imagine you reach physical maturity, say 18 years old, and you’ve got all the muscle fibers you’re ever going to have. All that muscle is divided up between these three types of fibers. Some people are born with predominantly Slow Twitch (red) Fibers. Think of Kenyan marathon runners – long lanky athletes who might even look fragile. Some people are born with predominantly Fast Twitch (white) Fibers. Think of weight lifters and 100 meter sprinters – stocky athletes who have thick rounded muscles. Some people are a split between the two: not so big and not so lanky. Now, what about those pink fibers? Well, a fortunate few have a good proportion of these (trainable) pink fibers. These athletes will adapt to which ever sport they subject themselves to. If they spend a lot of time doing resistance training they will excel at more anaerobic sports. Conversely, if they spend lots of time distance running then the adaptation will swing toward an aerobic fiber distribution.
Without knowing any of this, individuals self-select for the type of activity that they will excel at. Usually athletes will gravitate to the sport which best fits their “Fiber Distribution”. A person with lots of white fiber can still run a Marathon, but they won’t rise to the top of the field. I love distance running and I’m not too bad at it. But I also like weight lifting which I’m not built for – but I like it all the same. Many girls may hate their large thighs and big rear end, but that is a gift to someone who wants to go into short track speed skating or volleyball. Some skinny guys may wish for pecs of iron but for an aspiring triathlete – long and lean is the way to go. Don’t spend any time beating yourself up about your body type. Find something you like working at and start training yourself.
Muscle building myth
So let’s be clear on this: all you can do is train the fibers you’ve got. You can’t make more muscle. You can increase the number of sarcomeres inside the fiber (I mentioned those last time) but you never make more actual fibers. And if they get badly damaged like from a gunshot wound or a stabbing, then they are gone. That said, the intact fibers around an injury will strengthen and adapt and providing there weren’t too many destroyed then you might not notice the missing ones.
There is more information to come that will further illuminate how our muscles respond to training. I hope this is all taking shape in your mind. And I hope you feel inspired to awaken the athlete within you.