Bone is a highly vascularized and innervated connective tissue composed of cells specialized in synthesis (osteoblasts) and degradation (osteoclasts), and mechanosensory functions (osteocytes) [1] . These cells promote the constant remodeling of bone tissue throughout life based on functional demand and are arranged in a hydrated mineralized extracellular matrix. The latter determines the mechanical qualities of the bone, being formed by organic materials (collagen and proteins such as proteoglycans and glycoproteins) allowing better flexibility. Inorganic materials, whereas (calcium and phosphate), provide strength to bone tissue [2] . Collagen has thixotropic and piezoelectric properties which permit continuous adaptation to the mechanical stresses imposed on the tissues.

Bones have an outer (periosteum) and an inner (endosteum) lining. The periosteum is made up of dense connective tissue that surrounds the outside of the bone, except for the joints. It protects, nourishes, and aids in bone formation and fracture repair. The endosteum covers the inner layer of cortical bone and is composed of loose connective tissue [3] . Sharpey’s collagen fibers connect the periosteum to the innermost cortical regions of the bone as far as the endosteum, especially in areas exposed to increased mechanical stress. These fibers provide an important microanatomical continuity between the bone tissue components and their envelope [4] .

Measurement of stiffness, strength, and strain distribution of bones is extremely important for understanding bone biomechanics [5] , bone formation and adaptation [6] [7] , osteoporosis [8] , and fractures [9] .

The first experiments were carried out by measuring the torsional stiffness and strength of tibias and femurs whose samples were not tested in pairs, only some of the femurs and tibias came from the same donor [10] , while others, more recent, predicted the comparison between the right and left side of the same subject [11] [12] [13] [14] .

It is interesting to note how bones have a viscoelastic behavior, in which their viscosity varies as a function of the rate of deformation [15] and most of the deformation occurs in the first few seconds and represents 5% - 10% of the deformation immediately after load application [16] .

Going into more detail, with the increase in the speed of deformation, the rigidity of the bone increases [17] , this can be considered a form of defense of the bone itself since an increase in rigidity corresponds to an increase in resistance, but not only that, from the study, it was possible to notice how the resistance varies according to the direction of the deforming force, this means that the bones of the lower limbs are designed to deform in a certain way, they are optimized to withstand certain forces (Figure 1) [18] [19] .

One aspect to take into consideration is the difference between the bones of the right side compared to those of the left side.

We highlight some important conditions that directly influence the mechanical properties of bone:

- its deformation is not proportional to the load imposed on it;

- its mechanical properties vary according to the rhythm of the load;

- its mechanical behavior depends on the fluid present in the bone tissue;

- bone is composed of different types of bone tissue with different mechanical properties;

- its mechanical properties are not the same in all directions;

- is in constant remodeling and has different properties in different periods of life.

Mineralized matrix components promote strength, tension, and tensile-resistant collagen fibers that ensure bone tissue’s flexibility and impart energy-absorbing capacity. Hence, collagen property changes directly affect bone’s mechanical quality by increasing its susceptibility to fracture [20] .

The curvatures of the bones of the lower limb depend on the action of the forces applied to them, according to Euler’s law of “eccentrically loaded columns” (quoted by Steindler). When a column is articulated at its two ends (Figure 2a: free column loaded at both ends) the curvature occupies its entire height; this is the case of the posterior concavity curve of the femoral shaft (Figure 2b: lateral femur).

If the column is fixed at the bottom and mobile at the top (Figure 3a), there are two opposite curves, and the higher one occupies 2/3 of the spine: these curves correspond to that of the femur in the frontal plane (Figure 3b: frontal femur).

If the column is fixed at both ends (Figure 4a), the curve occupies its two middle quarters. This corresponds to the curvatures of the tibia in the frontal plane (Figure 4b). In the sagittal plane, the tibia has three features (Figure 5b) retro-torsion (t), posterior displacement; the retroversion (v) obliquity of 5˚ - 6˚ that tilts the tibial plateaus backward; retroflection (f), posterior concavity curvature of a mobile column at its two ends (Figure 5a), as for the femur.

The opposing concave curvatures of the femur and tibia increase the space available between the two bones in extreme flexion, which allows for a greater volume of muscle mass to be placed between the tibia and femur.

It is a similar arrangement to that of the elbow, where the curvature of the joint ends offers greater space to place the muscle masses during flexion [21] .

The term fascia is highly used nowadays, even if there is still an inconsistency in its definition. Recently, it has been proposed that the fascial system: “…interpenetrates and surrounds all organs, muscles, bones, and nerve fibers, endowing the body with a functional structure, and providing an environment that enables all body systems to operate in an integrated manner. It incorporates elements such as adipose tissue, adventitia, neurovascular sheaths, aponeuroses, deep and superficial fasciae, epineurium, joint capsules, ligaments, membranes, meninges, myofascial expansions, periosteum, retinacula, septa, tendons, visceral fasciae, and all the intramuscular and intermuscular connective tissues including endo-/peri-/ epimysium” [22] .

Regarding bone tissue, most of the definitions usually consider only the periosteum as part of the fascial system. However, for Sharkey [23] , definitions that do not include the other components of bone tissue as part of the fascial system are incomplete, as bone is a vital element for musculoskeletal continuity, and there is also a close embryological relationship between bones and the fascial tissue.

The author [23] points out that the concept of continuity of the fascial system also deserves importance when looking at the connection of ligaments and tendons in the periosteum, which in turn connects to the bone matrix through Sharpey fibers.

Bordoni and Lagana [24] , conversely, proposed that bone tissue represents a specific part of the fascial system, considering some relevant aspects such as the microscopic anatomical continuity of tissues, the embryological origin of bone and fascial tissue, the autocrine and paracrine tissue activities influencing itself and other body structures and systems, and the mechano-metabolic responses of bone cells.

From these remarks, the authors [24] describe a new definition of the fascial system, which includes liquid and solid structures (such as bone) and adds features to the fascial tissue such as the ability to support, divide, penetrate, nourish, and connect all structures of the body [25] .

In the medical literature, there are countless articles and publications on the efficacy of fascial manipulative treatment [26] [27] . Whereas the bone tissue is a tissue inserted in a fascial continuum, it is possible to treat the fascial tissue with specific techniques and treat the bone tissue acting on the periosteum and endosteum, even by making the bones more elastic.

Randomized double-blind selection of 38 people, men and women, aged between 16 and 35, part, for at least a year, in a sports club mostly dedicated to jumping training programs (Basketball, volleyball, handball, …), from November 2022 to February 2023, were divided into two groups:

- The supervised group (SG), consisting of 20 people, was exposed to mild manipulative treatment, without any intention.

- The treated group (TG), consisting of 18 people, with the purpose to increase the performance of the jump.

The standing long jump, also known as the standing broad jump, is an athletic specialty, included in the Olympic Games from Paris 1900 to Stockholm 1912. It was performed with the same principle as the long jump, with the difference that the athlete had to take off from the ground without running up.

When executing the standing long jump, the jumper stands on a line marked on the ground with the feet slightly apart. The athlete springs and lands using both feet, swinging the arms and bending the knees to propel forward.

The athlete was trained in the execution of the standing long jump, and he was offered the opportunity to perform as many tests as he felt necessary, in order to become familiar with the execution of that particular athletic gesture.

When the athlete felt ready, he was tested, performing the exercise as in the description in the previous paragraph, with 3 jumps. In contrast to the Olympic performance, in this study, all 3 jumps made by the athlete were considered, given the distance between the toe of the feet before jumping and the toe of the back foot in the case where the athlete landed with one foot in front of the other, after landing.

After the test was performed, the athlete was offered 2 folded tickets and asked to choose one, explaining that he would find 2 numbers, 0 and 1, and that he would not be told whether he would be in the treatment or control group, so as not to influence him, thus avoiding the placebo/nocebo effect (0 = No treatment, 1 = Yes treatment).

After the athlete selected the card, if he was in the treatment group, he was subjected to the treatment described in the previous chapter. Otherwise, it was subjected to placebo treatment that consisted of mild manipulations without any intention.

Following the treatment, the athlete was asked to perform a test leap, and after the test leap, the test characterized by measuring the three leaps was performed.