How Bodybuilding Works – The Science of Bodybuilding

Before you get started in bodybuilding, inspired and raring to go you may be, you need to understand how the act of bodybuilding works. Even if you’ve been bodybuilding for years on the other hand you should take the time out to learn this important aspect of the activity to give you an important competitive edge and advantage. By understanding the fundamentals of the science and principles behind weight training you can then start to learn why you’re doing what you’re doing – and also how to improve it and why some things work better than others. The more full your understanding before you begin the more you’ll be able to apply it to the moves themselves, so get ready for some heavy(ish) science babble.

The first thing to understand is how muscle grows as well as the structure of the muscles. Muscle growth in technical lingo is called ‘hypertrophy’ and it’s actually a response to stress that we have evolved over time. Basically the muscles are made up of muscle fibre. These are the cells that make up muscle tissue, and they’re different from other cells in a variety of ways. Notably they are endowed with two nuclei unlike most other cells in the body which only have one. This means that unfortunately they can’t replicate themselves via mitosis (splitting in half to create two identical copies) meaning that we’re limited to only a finite number of fibres in each muscle.

These fibres are made from amino acids constructed in much the same way as a telescope with the various layers ‘pedaling’ inside the others to generate movement. Essentially on a microscopic layer the fibres are made up of myofibrils which are made from sarcomeres. Sarcomeres are essentially tubes made of myosin and actin – and it’s the actin ‘pedalling’ along the inside of the myosin that generates movement.

To confuse matters further – and this can come in handy later – there are actually three types of muscle fibre (or ‘twitch fibre’). These are Type I, Type IIa and Type IIx – but are also known as ‘slow twitch muscle fibre’ (type I) and ‘fast twitch muscle fibre’ (types II and IIx – with type IIx being essentially ‘faster’ twitch muscle fibre). Due to a slightly different composition and different use of actin and myosin, the slow twitch muscle fibres are more useful for slow endurance tasks while the fast twitch fibres are more suited to fast explosive movements such as jumping and sprinting. Some animals also have type IIb which is even faster than type IIx and allows for the rapid change of direction (sometimes you will read type x labelled as type b incorrectly which can get confusing and is a throwback to a time before the current type b was discovered).

For this reason, someone with more type I fibres is going to be more naturally suited to endurance sports such as the 800 metres, whereas someone with more type II and IIx will be better at sprinting or jumping. While there is a genetic element in which muscle twitch fibres you have more of, research is showing that it’s possible to change a muscle fibre from one type to another with intense training. Other studies are suggesting that some fibres sit somewhere between type I and II, and that there may in fact be countless variations of muscle fibres. As we get older more of our muscle fibres become ‘hybrids’ of the two unless we continue training.

For a bodybuilder, all muscle twitch fibres are important and it’s a good idea to work both during a long workout. This is best achieved using a variety of different training techniques – plyometric exercises are designed to target the fast twitch muscle fibres, such as clapping press ups, clean and presses and box jumps. For the slow twitch muscle fibres, static contraction or isometric exercises that require the bodybuilder to hold a weight in a difficult position is the main order of the day.

When these exercises are performed it can cause the muscle fibre to tear slightly in what’s called a ‘microtear’. This is actually a good thing however, as this is how they will grow. Basically in response to the muscle tearing, the body will use satellite cells that wait in stasis around the muscles in order to fix the tears building them up more thickly each time they do to prevent against future damage (and possibly because this is just the way they are rebuilt – just as scar tissue is tougher than many of the cells it replaces). This will require more amino acids which the body gets from protein, demonstrating why it’s so important that the body has enough protein in its system – if a repair is failed to be carried out then it misses the chance and simply won’t happen. Should you cause multiple microtears and not have adequate rest and protein to make the repairs then the muscle will shrink rather than growing (this is called dystrophy).

When the body makes repairs to damaged tissue using protein this is called called ‘anabolism’ and is the opposite to ‘catabolism’ where the body burns carbs and sometimes muscle for energy. Someone with a fast metabolism is someone whose body is quick and efficient in carrying out both these tasks. Generally wakefulness is a catabolic state while sleep is an anabolic state meaning that most muscle growth and repair occurs in our sleep. However there are other ways to induce an anabolic state, with some supplements (surprisingly that’s not actually primarily what an anabolic steroid does) and with exercise itself – after we workout we immediately go into a recovery mode or an ‘anabolic window’ making it the best time to take protein.

Obviously as the muscles are repaired and become thicker they require a greater load and more repetitions to be torn and this is how and why we are able to increase the load that we workout with and lift more.

But in order to cause microtears and to do the necessary exercise your body will need energy to power the muscle fibres in closing and opening (expanding and contracting). This energy comes from a source known as ATP or Andenosine Triphosphate which is thought of in scientific circles as the energy source of all life. This substance is a nucleotide made up of three phosphogen molecules bonded together by a powerful force. That’s what the name literally means tri – meaning three, phosphate – meaning phosophogen.

The power in this substance however doesn’t come from the phosphogen itself, but from the powerful bonds that bind it together, and it’s when these bonds break that they unleash the energy that the body can utilise.

A bodybuilder needs to be able to supply his muscles with a lot of ATP then in order to perform the necessary movements in the gym – and there are three ways in which they can do this.

The first way the body gets ATP is through the phosphagen system which uses the ATP stored in the muscles and body to generate that energy. The body can store enough ATP at any one time to allow for around 3 seconds of full powered exertion, at which point it will need to look elsewhere.

Fortunately breaking the ATP molecules results in some useful bi products – ADP (andenosine diphosphate) and AMP (andenosine monophosphate) with two and one bonded phosphagen molecules respectively. So if you imagine you have three bonded molecules and they break you will understandably be left with one and two, or three single molecules. It’s basic maths… The good news is that using a substance called creatine phosophate the body can then recombine these molecules to make them back into ATP ready to be broken once again for more energy. The body can store enough creatine for roughly 8-10 seconds of continued exertion, meaning that in total the body can use the phosphogen system for around 13 seconds maximum of continued exertion which is enough to sprint just over 100 metres. It is thought however that through the use of creatine supplements that this maximum time can be increased.

At this point if exertion continues the body needs to get its ATP from somewhere else and this is when it looks to its stores of the carbohydrate glycogen in what’s known as the glycogen lactic acid system. This is a slightly slower and less efficient system, which requires the body to split the glycogen first into glucose and then again into ATP. This unfortunately creates a rather unwanted by product of lactic acid (from which the substance takes its name), which creates the uncomfortable mildly painful ‘burning’ sensation we get in our muscles when we push ourselves in the gym. The body can sustain itself using the glycogen lactic acid system for a further one minute and thirty seconds.

Both these systems are anaerobic, meaning that for the first one minute fourty three seconds the body won’t be using oxygen or burning fat. In order to lose weight then the training must continue past this point and force the body to find its energy elsewhere. This is where the aerobic system comes in, relying on the oxidisation of foodstuffs in our mitochondria. In other words the body looks to our supplies of glycogen (and so ATP) stored in our cells as fat and then uses the oxygen in our blood to break them down and carry them to our muscles. This will start off burning fat (in no particular order other than that genetically determined by your body’s physiology) but eventually move on to burning muscle if you continue the exertion for too long as the body literally cannibalises itself. The aerobic system can last indefinitely until it begins to do more harm than good to the body.

So that’s basically it, how the body powers itself and re-grows and strengthens muscle. As you read the advice in various books and bodybuilding articles you should now be able to understand why it works the way it does, and at times we will reference the underlying processes to outline how and why each method or supplement works. If you’ve survived until the end of this article then well done – you’re now officially one step ahead of most bodybuilders who start their training without any underlying scientific understanding of the sport. Knowledge is power, and you’re now armed with a proper understanding that can help you adapt and tailor your own training and assess new programmes or supplements yourself as they come.

Comments 8
  1. Lots of baseless claims made, some that have had research show the opposite is actually true (muscle growth occurs WITHOUT any muscle damage or micro tears happening), etc. Also redefines what anabolism is based upon what its defined as in multiple dictionaries. And no science or research articles are referenced for the reader to check up on the statements made.


  2. I thought this article was pretty good put together all the pieces of knowledge I've read in other places.

  3. Great article that summarizes the science of bodybuilding well.

    Though it is not proved that it is lactic acid itself that causes pain in the muscles during exercises but must likely the nerves responding to the hard work.

    "This unfortunately creates a rather unwanted by product of lactic acid (from which the substance takes its name), which creates the uncomfortable mildly painful ‘burning’ sensation we get in our muscles when we push ourselves in the gym."

  4. Very informative article, glad I came across it. Can now use this info to further my training in the right direction instead of guessing my way along. Thanks a lot!

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