Muscles that assist an agonist in performing a movement are known as synergists…Some of the terms that any strength-training aficionado learns are agonist, antagonist and synergist. After years working as a personal trainer in Valencia I have heard all kinds of discrepancies between amateurs but also between colleagues.
muscles that assist an agonist in performing a movement are known as synergists.
This categorization aims to understand the function of each of the muscles involved in each exercise or movement. However, if we want to correctly understand the network of muscles that lead to the efficient performance of each gesture, we may fall short of the conception that most amateurs, and some personal trainers and physical trainers, have of the agonist, antagonist, muscle concept. synergist and stabilizer.
To explain it in a simple way I will use an exercise as simple as the extension of knee in machine. More useful and complex exercises like the squat or deadlift would open a debate that would take us away from the original purpose of this article, which is simply understanding the different concepts and terms correctly.
The agonist muscles are responsible for the main action of the movement. If we had an electromyograph at hand it would be those muscles that support most of the protagonism. Because there is no limit that clearly marks the difference between protagonist and secondary actor, the line that differentiates between agonist and synergist is fine and not always clear.
In the case of extension of the knee in machine, the main ones would be femoral quadriceps: rectus femoris (rectus femoris), vastus medialis (internal), vastus lateralis (external), vastus intermedius (cruralis) and articularis of the knee.
The antagonist muscles perform the opposite action to the agonist. They oppose the action of the movement but not enough to prevent movement. Nor are they completely inhibited because their co-contraction, as well as the correct set of tensions between the muscles that act on both sides (agonists vs. antagonists) is necessary to keep the axis of rotation around which the movement is stable.
In this case it would be the hamstrings or hamstrings: biceps femoris, semitendinosus and semimenbranoso. The gluteus maximus would be considered knee flexor and, therefore, an antagonist in this exercise because it is inserted into the iliotibial band and, therefore, crosses the axis of flexion of the joint. The gastrocnemius should also be added, since they are knee flexors, popliteal, plantaris.
Synergistic and stabilizing muscles
The stabilizing muscles will always be synergistic, since only the synergies (hence the synergistic term) that arise from joint work is efficient and controlled movement. However, not all synergists will be stabilizers. Stabilizer will be the one that, thanks to the geometric arrangement of its fibers, will have the capacity to maintain the alignment in the articulation and stable the axis of rotation.
In the case of knee extension we would have as stabilizers all antagonists that, because the axis of flexion is virtual and not physical, should maintain the stability of this axis. In case the axis was physical, such as the wheel in a horse cart, or on a skateboard crossing the bearings, the antagonist muscles would not be necessary for this purpose, because the fixed axis would maintain the position. Since the joints of living beings do not have a fixed physical axis, it is the muscles themselves, specifically the antagonists, who must take charge of maintaining the stability of the joint by creating a virtual axis on which rotation takes place.
The stabilizers would be: popliteus, the tensor fascia lata (TFL), gastrocnemius, sartorial, graceful and plantar. Furthermore, if we start from the base, as explained, that the antagonist muscles have a determining role when it comes to creating and maintaining an imaginary rotation axis stable, it would be necessary to introduce the rest of the knee flexors in this category as semitendinosus. , semimenbranoso and femoral biceps.
As you can see, it is not as simple as many believe. However, although it may seem complicated to know the name of each of the muscles involved, what is really important is to understand the role that each of them plays in the realization of harmonious, precise and efficient movements. Having understood this, we will have time to ask you and remember your name and surname knowing that, in any case, it will always have a minor importance.