By Dr. Antonio Parolisi
Biomechanical and functional considerations on the lateral lift movement
A movement that allows a great involvement of the scapulo-humeral belt is undoubtedly the exercise of lateral raising, as mono-articular, or slow forward as a multiarticular exercise.
In the lateral elevation, in practice, abduction occurs on the frontal plane, which in order of activation includes the muscles: supraspinatus, deltoid, trapezius, dentate gran, and contralateral lumbar.
When the question arose as to whether the slow forward (military press) hurt the low back, or that in any case stressed the lumbar area, many were perplexed, especially when it came to exercises performed even with only 5 kg.
Those who neglect joint mechanics believe that the excessive load used in an exercise, such as the slow forward, affects the comfort situation of the back. The point is that this is true but only in part, because, even if important loads are not used, the mere gesture of bringing the arms over the head tightens the lumbar muscles that intervene in the last third of the movement. It should be noted that when the arm is slightly raised or at ear height, the contralateral lumbar is activated, but in a lower percentage than the deltoid and trapezius.
The sequence is illustrated and explained in the text of IA Kapandji "Articular Physiology" which perhaps represents one of the most famous authorities in the sector.
This text defines "the three times of abduction". In the first phase the protagonists are the deltoid and the supraspinatus. It ends at about 90 °, when the tubercle of the humerus touches the edge of the scapula. At this point the physiological action of external rotation takes place which allows to continue with the excursion upwards. Already in this first phase a debate could be opened over entire days, as the majority of fitness technicians recommend the exercise of sideways lifting with the thumbs looking downwards, with the conviction and presumption of having the "fibers of the lateral deltoid ".
The biomechanics speaks clearly !!!
If the blessed humerus does not rotate externally, the movement of elevation of the arm cannot take place, because it would create a conflict with the glenoid of the scapula, preventing the movement of the movement. So ultimately it would be more "natural" to perform a movement with an external rotation of the arm (with the thumbs, so to speak facing upwards).
In the second phase of abduction the leading muscles become the trapezius and the large dentate, as they are responsible for the rotation of the thoracic bachelor; therefore the intervention of the scapula in this second phase through a lateral tilt is clear. Let's say this happens between 90 ° and 150 °.
In the third and final phase of abduction the protagonists become the spinal muscles which, to allow the verticalization of the arm, enter into contraction, determining also a lumbar hyperlordosis, necessary to increase the range of abduction.
The phases are only descriptive but the muscles are activated "all", even from the slightest detachment in abduction of the arm. Only the intensity of the contraction will be modulated, as the excursion increases.
The recurring question that must be done in Personal Training is always the same!
How do I understand if this exercise is indicated for a person or not?
Once again, we need to test the subject!
First of all, to assess whether he is already in a hyperlordosis position, since during the exercise this curve is markedly accentuated; this principle applies "all" the times you raise your arms above your head, then in the Lat machine in the Pullover or in the Slow forward.
In this case it would be ideal to limit the movement when the lumbar tract begins to arch, therefore not necessarily, as many claim, at 90 °, but when the marked and evident lumbar intervention occurs. It is likely that in a subject with a hypolordosis this never occurs.
Another myth to debunk is that when you get to 90 ° the deltoids work, then, beyond this angle, the trapezoid works.
Then a question arises spontaneously. The slow forward exercise because it is prescribed in the deltoid muscle training cards when it is a movement that already starts at 90 degrees ??
If this were the case in the military press, only the trapeze should work because it starts from over 90 °!
The reality is that explained in the joint physiology: as soon as the arm is removed from the side, the muscles mentioned all intervene in different proportions in the various arcs of movement.
The thing to understand at this point is that the side lift should include all the movement: from the sides of the thigh to above the head.
Wishing to be cautious from the point of view of safeguarding the joint, one should start from a position of already partial opening of the arms from the thighs, to avoid excessive compression of the supraspinatus tendon.
This is what it should be, but the question is always the same: we cannot know the abilities of a single subject beforehand, so we must adapt the movement to the qualities and possibilities of the individual person.
If the triceps are retracted, the movement will be limited but will still continue at the expense of the contralateral lower back musculature, which will be forced to compensate to allow continuous movement; if then the subject is under a "Shouders press" machine that does not provide an escape route, you can imagine the compressions to which the other structures are subjected.
What is said if one has a large dorsal retracted or in any case not adequately elastic, there would always be phenomena of compensation, which in the long run would lead to lower back pain due to excessive stimulation of the stressed area. We may add a few hyperextension exercises for the lower back and we have prepared a nice recipe for chronic pain.
The elasticity of the internal rotator muscles of the shoulder deserves a lot of attention. If they do not have good flexibility, they will require an intrascapular compensation.
CONTINUE: Part Two »
