The main muscles of the body for bodybuilding

If you are a complete novice, you might not be able to tell your deltoids apart from your lats, or your quads from your traps. Yet you will most probably know your biceps as they are one of the most popular muscles to train, despite their small size. Let’s get you up-to-date with the various muscle groups of your body so you know what to train and what you are training.

Human muscle anatomy

The legs

The quadriceps are made up of 4 muscles on the front of the legs that serve to extend or straighten them. They are one of the biggest and most powerful muscle groups of your body. Opposite the quadriceps, on the rear of the legs are the hamstrings, whose function is opposite to that of the quads – bending the leg at the knee to bring the lower leg close to the upper leg. Below and behind the knees are your calves, made up of two muscles. They serve to raise yourself on tiptoes so they are used pretty much every time you walk or run. The glutes are the muscles in the bum. They straighten your body or move your legs backwards. So if you stand up from a squatting position, you are straightening your body and therefore recruiting these muscles.

The chest and front area

Now to the upper body. The abs are the stomach muscles curling the torso and the legs towards your navel. The obliques are the muscles on the side of the abs that perform a similar function but from the side.

The pectoral are the chest muscles whose function serve to extend the upper arm straight out in front of you and bring it closer to your centre in a movement akin to punching someone. This is a complex movement that also involves the triceps, 3 muscles at the back of you upper arm that extends the forearm from the upper arm, and the deltoids.

The shoulders

The deltoids are 3 muscles at the top of your upper arms making up your shoulders. Every time you raise or move your arms, the deltoids are involved. The front or anterior deltoid lies at the front and is heavily involved in all pectoral exercises as it serves to raise the arm to the front. The exterior deltoid is the muscle on the exeternal side of the upper arm – it raises the arm to the side. The posterior deltoid is found to the back of the upper arm. It is not directly involved in chest exercises, except to act as stabilisers to the anterior deltoids. The posterior deltoid brings the arm back to the body and is heavily involved in back exercises.

The back

The back is the largest and most complex muscle. In fact, it is made up of several muscles groups that all work together. The lower back, made up of the erector spinae, extends the upper body, for example when you straighten up from bending at the waist. It does to the upper body what the glutes do to the lower body. The latissimus dorsi, lats for short, are a wide triangular-shape muscle on each side of the back that tapers down. They serve to pull the arm back or down. When fully-developed, they give an inverted V-shape to the upper body, a much-sought after appearance.

The last major muscle of the back is the trapezius, traps for short. Many people think the traps are the shoulder muscles. You can see them from the front at the base of the neck. That part is called the upper trap. Every time you lift your shoulders in a shrug movement, the upper traps are working. Most deltoid exercises will involve the upper traps. However, the upper traps make up but a small proportion of the whole trapezius. This muscle group gets its name from its shape when viewed on the back – a trapezium shape. The middle and lower traps on the back serve to pull back your shoulder blades.

The biceps serve to bring the forearm close to the upper arm and to turn the forearm slightly with the palms facing you.

Antagonistic muscles

By now you would have noticed that muscle groups perform opposite movements: triceps versus biceps, back versus pecs, lower back versus abs, quads versus hamstrings and so on. Antagonistic muscles perform the opposite movement of agonistic muscles. It is important to work all areas of the body equally to keep all muscles balanced out with each other. If you work only your quads and don’t care about your hamstrings because you cannot see them, one muscle group becomes more powerful than the other, creates a muscle imbalance at the pivot point which in this case is the knee and may easily lead to an injury.

Muscle groups also work in synergy with one another. It is not possible to completely isolate one muscle from another in any movement or exercise. So even using the bicep muscle will involve the deltoid to some extend and if you are standing, your back and

to a lesser extend as you balance your body against the movement of a heavy weight.

Some exercises involve other muscles even more. They usually involve complex movements and are called compound exercises. The squat is such an exercise. Simply imagine someone squatting down and getting up again. A lot of balancing act is required, especially if you add a heavy weight on the person’s shoulders.

Muscle types

The composition of the muscle itself is important but at this level of detail, we will end up at the cellular level of the human body. Suffice it to say that there are broadly two types of muscle fibres, the fast twitch and the slow twitch. The latter has endurance and is used in cardio activities. The former has power but gets tired quickly. This is what we target to build muscles in weight-lifting as it has the potential to grow rapidly under stimulus. As slow twitch fibres are used in repetitive movements, the legs have a higher proportion because we use them frequently for walking, and the calves in particular have a high proportion. So the way to train them is with high reps.


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