Nevertheless, it is always necessary to carefully evaluate the specific case, to avoid aggravating, exacerbating or even establishing de novo joint, tendon and muscle problems.
The chances of injury increase in the presence of some predisposing factors; among the most common, muscle retraction, stiffness and weakness, and related compensations that tend to burden the joints.
In this short article we will examine the correlation between hamstrings (hamstrings) and rachis (spine), trying to understand how performing a common exercise such as leg curl can improve or worsen back health.
-peroneus-tibial or simply posterior femoral, that group of muscles is identified which, from the ischial tuberosity and the sharp line of the femur, are inserted:
- on the head of the fibula (hamstring);
- on the back of the tibia (semitendinosus and semimembranous).
These muscles therefore have a bi-articular action, because they flex the knee on the thigh and extend the hip.
and position: prone, standing, sitting;The leg curl can be practiced in a monopodalic or bilateral way.
Note: The leg curl can also be performed with elastic or ankle braces (in a standing position).
How to perform the leg curl
The execution of the leg curl is quite simple, since it is a one-joint exercise - some call it isolation, even if in fact several muscle groups are involved.
Assuming the starting position - prone or standing - the feet are locked behind the stops, stabilized at the front by grasping the special handles, and flexing the leg / legs, trying to reach the minimum physiological degree of the knee.
The eccentric phase, which must always be controlled, will end at the complete extension of the knee but without losing muscle strength; this would leave the weight on the joint.
In the vast majority of cases, the main recommendation of the instructors describing the leg curl exercise is to stretch the hamstring muscles before, during and after the exercise. This is above all for preventive purposes on injuries and to optimize joint ROM - but remember that those who suggest doing it to better recover and reduce DOMS make a substantial mistake.
Paradoxically, the simplicity of execution of the leg curl is also its weak point. The strength machine, especially the one in the prone position, must be carefully adjusted.
The foot rests must rest on the Achilles tendon, not on the calf and not even on the heel - those with problems in this area, of course, will have to avoid.
The knee must come out of the profile of the support bench, so that the patella does not rest.
Some machines designed for the prone position have the possibility of giving the top a certain degree of angulation, a characteristic that reduces lumbar hyperextension and - as we will see below - can therefore prove to be very useful in certain situations.
-psoas and rectus femur) and the leg extensors (quadriceps femoris).
But what do the anterior muscles center with the hamstrings? It depends, above all, on the variant of leg curl taken in question.
During the shortening of the hamstrings, there is a flexion of the knee and an elongation of the anterior muscles, in particular the quadriceps.
In the prone position (lying belly down on the bench) there is already an elongation of the anterior chain by partial extension of the coxo-femoral joint.
When the hip flexor muscles are retracted or stiff, or if the antagonists are too weak, compensatory lumbar hyperlordosis is likely to occur.
In this situation, the iliopsoas and rectus muscles of the femur passively "pull" the vertebrae from the 12th thoracic to the 4th lumbar vertebra, placing the pelvis in anteversion, and putting stress on the intervertebral joints which in the long run can degenerate due to overload.
Therefore, in conditions of already evident disc pain, such as in the presence of protrusions or herniated discs, a similar error could lead to considerable problems.
The exercise in question was born with the aim of training and increasing the trophism of the hamstring muscles but, if there are "subjective" contraindications, it must be used sparingly and modified if necessary.
.The test that is most suitable for comfort and practicality is the Thomas test, in which the person lying in the supine position must bring the knees to the chest, alternately; this is how the dysfunctions in flexibility of the muscles under examination will be assessed.
In this specific case we will observe the rectus femur and the ileo-psoas (hip flexors) which, to show a good elasticity, by gathering one thigh to the chest, will see the other remain well supported on the plane and the knee relaxed.
Conversely, a partial shortening of the hip muscles with less emphasis on the knee extensor muscles will cause the popliteal fossa to lift off the bench, indicating that the ileo-psoas or rectus muscles of the femur or both have little extensibility.
This does not recommend the practice of the prone leg curl, as the starting position taken traction the lumbar vertebrae by the ileo-psoas or anteriorizes the pelvis by the rectus of the femur or, in the worst case, due to both traction lumbar curve in hyperlordosis and anteriorizes the pelvis.
On the other hand, the seated leg curl, in which a large hip extension is not required, would be less stressful or safer. By using this exercise, the flexors will be prevented from pulling the vertebrae and pelvis as in traditional leg curl.
An extremely important concept should be taken into consideration, that of mono-laterality: if on the one hand the muscles are not very flexible, it does not mean that on the other hand they must have equally scarce flexibility.
It often happens to observe subjects with a really evident difference in terms of elasticity from one side of the body to the other. A particularly retracted rectus of the femur could be the consequence, for example, of an "anteversion of a" hemibacin "that traction musculature inserted forward, causing a shortening of the inserted muscles.
If a person presents with muscles retracted on one side only, unilateral stretching will be useful again. Therefore only those muscles that prevent the correct execution of the movement should be stretched.
Finally, during the test, an important retraction of the hip flexor and extensor knee muscles could be observed. Attention should be paid to the marked lifting of the popliteal fossa from the bench-table and to the extension of the knee by the quadriceps muscles.
It should also be noted that this could lead to greater cervical lordosis, an evident sign of the need for a global lengthening, according to the concept of muscle chains.
In this last case, therefore, the hamstring muscle exercises must be contained and perhaps even avoided, as the practice of leg curl, both prone and seated, would lead to damaging compensation at the level of the back.
The primary objective in this case is to re-establish maximum joint excursion, to allow the muscles to work in complete ROM.
The study of flexibility in a training program is therefore essential in order to avoid compensations that can also weigh heavily and degeneratively on the stressed segments.
