This is an excerpt from Strength Training Anatomy Workout II, The by Frederic Delavier & Michael Gundill.
Segmenting Muscles So You Can Dominate Them
You need to know whether each one of your muscles is polyarticular or monoarticular. To understand the difference, consider the example of the brachialis and the biceps:
>The brachialis is monoarticular, because it attaches to the forearm and the humerus (arm bone): It only covers a single joint.
>The biceps is polyarticular, because it attaches to the shoulder and the forearm (not to the humerus): It covers two joints.
To separate the various functions of polyarticular muscles, we can focus on the length-tension relationship. We will have to divide monoarticular groups in a more artificial manner.
The Length-Tension Relationship
The tension (strength) of a muscle is not uniform. When a muscle is stretched to the extreme, it has very little strength. The same thing happens when a muscle is shortened to its maximum. We can conclude that somewhere between these two extremes is the point where a muscle has the best chance to express its strength. So each muscle has an optimal length at which it can mobilize its maximum power. The farther you stretch the muscle from its optimal length (either by stretching or by contracting), the less effective it will be. This means that you will not be able to recruit it and contract it with power.
The concept of the length-tension relationship might seem abstract, but you must understand it when you are working polyarticular muscles such as the biceps, triceps, hamstrings, and calves.
Segmenting the Biceps
The biceps is made up of two heads (parts). With the strategy of segmentation, the idea is to separate the workouts for these two heads so that you work one head while the other head is recovering, and vice versa. This way, you can work the biceps more often, despite an incomplete recovery.
In practice, when you push your elbow toward the back, the following occurs:
>The long head of the biceps (outer part) is placed in a favorable length-tension position.
> The short head of the biceps (inner part) is placed in an unfavorable length-tension position.
result:The long head takes control, leav-ing the short head less able to contract. The benchmark exercise here is an incline curl done on a bench (as flat as possible) using a dumbbell.
However, when the elbow is in front of the body, the following occurs:
>The short head of the biceps works first.
>The long head has more difficulty getting involved.
This is the case with most biceps machines and Scott curl benches. So, by changing the stretch in your biceps, you change each head's ability to participate in the movement. When you work out, you can do either of these:
>Work the biceps from both angles.
>Work the biceps from only one angle.
If you are focusing on only one angle, the first workout can target the short head, and the second workout can focus on the long head. For the third workout, begin the cycle again.
Segmenting the Triceps
The long head of the triceps (inner part) is polyarticular. The other two heads are monoarticular. To increase the recruitment of the long head, you need to stretch it, which puts it in a favorable length-
tension position. To do this, you must choose triceps exercises where your arms are placed close to your head. During the next workout, you can accentuate the work of the other two heads by putting your arms alongside your body with your elbows as far back as possible.
Segmenting the Shoulders
Even though the deltoid is monoarticular, this muscle can be divided into three parts:
>The front (anterior)
>The side (lateral or middle)
>The back (posterior)
The first workout, based on presses, will target the front part of the shoulder. The second workout will focus on the back part, and the third will work the side. Then you will begin the cycle again.
Segmenting the Back
In strength training, most people think there are two main categories of back exercises:
>Those that work on size (primarily the latissimus dorsi)
>Those that work on thickness (trape-ius and rhomboids)
This distinction, even though it is very artificial, will work for our purposes. Instead of combining pull-ups and rows in every workout, you can devote the first workout to pull-ups (for size) and leave the rows (targeting thickness) for the next workout.
Segmenting the Chest
The chest can be divided into two sections:
>The upper section
>The lower section
People often try to stimulate both sections every time they work out. However, you should try to concentrate on only one part in each workout. For this segmentation technique to work effectively, you must have already learned how to isolate the upper part of your chest. The easiest way to learn this is to perform light cable work that targets the section of the pectoralis major nearest to the clavicle.
Segmenting the Abdominal Muscles
Segmenting the abdominal muscles is easy. You need to work these sections:
>The upper section
>The lower section
Therefore, alternating between specific exercises for each region is very simple.
Segmenting the Calves
The gastrocnemius muscles are polyarticular, but the soleus is monoarticular. If you work from a seated position, you make your gastrocnemius muscles soft, and they can no longer contract.
However, the straighter your legs are, the more the gastrocnemius muscles will be stimulated. Ideally, you should lean forward (as in donkey calf raises or leg presses) to find the ideal length-tension position for the gastrocnemius muscles. You can do one workout with straight legs and another workout while seated with bent legs.
Segmenting the Hamstrings
The hamstrings have two functions:
>To flex the leg (e.g., in leg curls)
>To straighten the torso (e.g., in a deadlift)
Focus on the first function during one workout, and then focus on the second function during the next workout.
Segmenting the Quadriceps
Our strategy of dividing muscles into parts does not work here because it is difficult to divide up quadriceps exercises. Instead, you can use a strategy of alternating between using machines and using a bar. This will allow you to rotate through three main exercises:
Instead of using two or three exercises per workout, you should concentrate on only one exercise.
Read more from The Strength Training Anatomy Workout, Volume II by Frederic Delavier and Michael Gundill.