There are three primary muscles groups in the back – the trapezius muscles in the upper back, the latissimus dorsi muscles in the mid-back, and the erector spinae muscles in the lower back.
There are several other smaller muscles in the back, all of which will be developed by performing exercises that work the three main back muscles.
The trapezius (traps) muscle is made-up of three separate regions. The upper portion of the trapezius is mainly responsible for shrugging your shoulders. The middle and lower regions are used during rowing type movements. Well developed traps help to counterbalance the chest and front (anterior) deltoids. This helps to improve posture and reduce the risk of injury.
The latissimus dorsi (also known as the “lats”), lie across the middle section of the back on each side. This muscle group when well developed gives the upper body that V shape. The lats originates from attachments along the spine and inserts with a large tendon to the humerus (upper arm bone) on each side of the body.
The erector spinae muscles of the lower back are like two thick columns of muscle on either side of your spinal column. The spinal erectors run from the base of your pelvis to almost the full length of your spine. However, they are most easily visible from the middle to the lower back.
There are four main muscle groups in the thighs. The quadriceps on the front of the thigh, the biceps femoris on the back of the thigh, the leg adductors on the inner side of the thigh, the leg abductors on the outer side of the thigh. There are several other smaller muscles as well, but they will be completely developed if you focus on working the four main thigh muscle groups.
The quadriceps muscle has four lobes, and it primarily is used to straighten the leg from a bent position. This muscle is often called the “quads”. A secondary function of the quads is thigh adduction and rotation of the thigh within the hip socket.
The bicep femoris (also know as the hamstrings or leg biceps) consists of two lobes, and it primarily is used to bend the leg from a straight position.
The adductor and abductor muscles of the thighs help to pull your leg either toward the centre line of your body (adduction) or away from the centre line of the body (abduction).
The gluteus (also know as the “glutes”) form your buttocks. This large muscle is primarily used to extend the leg into a straight line with the torso and to rotate leg at the hip.
The pectoralis muscle is a large flat, fan shaped muscle that covers the entire upper rib cage. It originates from attachments along our breast bone, collarbones, ribs, and it inserts on each side of your body via a large tendon through your shoulder joint to your upper arm bone.
The primary muscle of the shoulder is the deltoid (also know as the “delts”). It is the rounded cap over the point of your shoulder. There are three heads of the deltoid that insert into the upper arm bone. The anterior (front) head, the medial (side) head, and the posterior (rear) head.
Around the shoulder joint itself is a small bundle of muscles called the rotator cuff. These smaller muscles help to rotate the arm in its shoulder socket. Since these muscles are small relatively weak they can be injured easily. That is why it is essential to warm up well before working your shoulders or doing any activities that incorporate the shoulder joint.
When training the abdominals you should pay attention to the three primary areas of your midsection – the rectus abdominis (frontal abdominal wall), obliques (muscles at the sides of your waist), and intercostals (bands of muscle that run diagonally across the sides of your upper abdomen).
The arms consist of three main areas – the biceps, triceps, and forearms.
The biceps is actually a smaller muscle then the triceps. It is on the front of the upper arms. There are two heads of the biceps muscle (hence the bi in biceps).
Beneath the biceps is the brachialis, a flat muscle group that runs about half way up the upper arm bone from the elbow joint. From the rear you can see the brachialis as a well-defined band of muscle between the triceps and biceps when a muscular bodybuilder flexes his/her arm.
The triceps is a three-headed muscle that is on the back of the upper arm (hence the name tri in triceps).
It is essential that when you do any exercise that you perform the movements correctly, if you don’t you will receive less then optimum benefit from the exercise. It is very difficult to unlearn bad exercise habits, so it is best to learn the right exercise technique from the very start.
The key to developing the arms is to avoid overtraining these small muscle groups. The arms are used as secondary muscles in almost all chest, back, and shoulder exercises. For example, the biceps are used when doing any type of rowing movement for the back. The triceps are used when doing any type of pressing movement for the chest and/or shoulders.