In Part 1 of this series, I made the point that the third pull and second pull can be considered as the same pull. Following this, I would like to expand on muscle sequencing, on its definition, on its importance in coaching weightlifting and on weightlifting efficiency. Understanding proper muscle sequencing is key to coaching the right positions and to demanding the right outcome of the lift. In the next part of this series, I will explore different pulling styles and how it affects muscle sequencing (favour certain muscles) and ultimately, your results. Do take a look at the follow included in this article as they are example of different muscle sequences.
Muscle sequencing is defined by the order by which muscles are being recruited/selected to contribute to the movement – or the movement’s goal. In other words, the nervous system recruit muscles according to their action and it does so according to a temporal code.
The wanted action is not necessarily the action of the isolated muscle, but more so the sum of all muscle actions coordinated to do the wanted motor output or behavior (ie : a jump, a throw, etc.). Such simple actions involve incredible, elegant but complicated neural mechanisms. That is, the CNS finds a way to inhibit muscles to a certain degree or recruit muscles according to the action as well as the biomechanical context.
The temporal coding – or the timing of the recruitment – depends on the action of the muscles as well as on biomechanical realities such as joint angles and the influence of such angles on musculature (potential for force generation, potential for contribution to the movement, reflex activities, etc.). Simply put, at some given joint angles, a muscle can either be favored or inhibited/not favored in the context of movement. This can either be good or bad depending on the goal of the movement.
Let’s use a weightlifting related example. Raising the hips very quick off the ground (much faster than the bar moves vertically) is considered a technical mistake as it will sacrifice the knee extensors (quadriceps) contribution to the movement of the snatch because (1) the bar has not moved and (2) the knees are now close to being fully extended limiting any type of future contribution passed the knees.
In this context, the back is being favored as its angle will change resulting in the favoring of back extensor muscles (going from an approximate 45degrees to being horizontal/parallel to the ground). Such motor sequence is detrimental to the goal of a snatch or clean, but it is however often witnessed or coached in the deadlift where the deadlifter will even start with his hips in a rather high position for this particular reason.
Proper muscle sequencing translate in high efficiency and great power output. Proper muscle sequencing in weightlifting is the ability of the weightlifter coordinate the action of all the major muscle groups in the proper order so that the lift can be made. A mistake in timing is a mistake in muscle sequencing. Improper muscle sequencing is what technique refinement is supposed to correct.
Muscle sequencing in the Snatch and its challenge
I will use the example of the snatch to better explain muscle sequencing within its context. The biomechanical system of the lifter could be explained in a relatively complicated fashion. We could talk about every joint, every muscles and every force applied to the system or developed by the system. Modelling the biomechanical system of the body is one the biggest challenge in biomechanics.
For our purpose, however, we could define the system by the muscle groups (prime movers and their synergist muscles) who are involved in doing relatively the same action/behavior. Thus, for our purpose I have identified 4 groups of interests that are implicated in making the bar move up. The list would change slightly if we looked at how the body moves to catch the bar at the bottom of the snatch.
1) The knee extensors are the biggest contributor to a vertical acceleration of the bar (they make the bar move up). In some pulling style, we could pair the knee extensor with the ankle extensor
2) The hips is directly responsible for the forward movement of the bar and indirectly responsible for vertical movement of the bar as a loop is a loop (the hip accelerate the bar forward but since the bar is attached to the arms some kind of vertical acceleration will happen). Such indirect vertical acceleration from the hips, which involves the loop, is unwanted as the sacrifices are too big for the benefits. You could list hamstrings as synergists here. The glutes do help straightening the body though.
3) The back is responsible for rearward movement of the bar and indirectly some kind of vertical movement. Same as with the hips, such indirect vertical acceleration of the back, which happens due to the way the bar is attached to the body, is really unwanted as the sacrifices are too big.
4) The arms and shoulder complex contribute to some kind of vertical acceleration but not as prime movers. They will however help guide the bar to the right spot given that proper momentum was imparted on the bar.
In this very simple sequencing attempt, we have identified 4 different groups that contribute to the movement of the snatch in different ways. We have 1 group that is better suited for vertical acceleration /vertical power output, 1 group that is better suited for forward movement of the bar, 1 group that is better suited for rearward movement of the bar and 1 group that may contribute to vertical power out but does so more as a guide.
The success in the snatch depends on the interaction between these four groups. In other words, a successful lift is the result of well calculated forces applied on the bar which come from different groups, meaning that there is a vertical, a forward and rearward projection of the bar.
Now that we have our groups listed, the right question to ask is in which order should these groups be recruited?
The shoulder and arms (group 4) guide the bar once it gathers momentum, thus they should be the last muscles to be recruited when snatching. Since the hips (Group 2) mostly make the bar move forward, its action has to precede the action of the back (Group 3) as the role of the back here is to counter the forward movement of the bar.
There is, thus, a very tight connection between the hip and back that has to mastered and refined, as too much hips or too much back results in excessive horizontal movement of the bar (ie : loosing the bar forward or behind). The top part of the S in the pull is exactly the result of the interaction of the hips and back. Group 2, 3 and 4 can only efficiently contribute to the movement if enough force was developed by group 1 (the knee extensors) as both the hips, the back and shoulder add their respective force to the initial force that is generated by the legs.
Any mistake in muscle sequencing here, such as using the arm too early, will increase the chance of missing. Some lifters are proficient with improper muscle sequencing (some pull with bent arms for instance), but in the grand scheme of things and according our concepts here, they would, at least in theory, do more if the sequencing was better suited.
Moreover, our description here shows that the legs are the most important contributor to the movement of the snatch. However, with any hip or back action the bar cannot be locked correctly. The bar has to move somewhat forward so that it can go behind the head. After all, the bar is in front of the body and has so go above the body which suggest some kind of rearward displacement of the bar which can only be achieved through the very calculated use of the hips and back.