It is known that physiologists and physiotherapists attribute to the conventional sitting position a whole variety of problems referred to as "back pain".

Flexing of the hips, which is a characteristic of the conventional sitting position, in fact causes an increase in the pressure between the discs and stretching of the rear ligaments of the vertebral column.

In these postural conditions, the lower part of the back ceases to perform its supporting function and the force generated by the pelvis to support the upper trunk is replaced by contraction of the shoulders, creating tension in the neck and the back of the neck.

The correct sitting position is one which favours a balanced energetic state. This state is associated with the elasticity of the body, i.e. with the ability of the body to stretch and contract, as required, without the accumulation of permanent tension. Of particular importance is the elasticity of the dorsal spine and lower part of the abdomen, which is the seat of vital energy.

A more immediate sitting position is one on the ground, either with the legs crossed, i.e. the Indian "lotus" position, or with the buttocks resting on the heels,

i.e. the Japanese "seiza" position.

These sitting positions on the ground allow the balanced distribution of the weight of the upper trunk on the buttocks, maintaining the function of supporting the lower part of the back and the possibility of causing the flow of energy in the lower part of the abdomen.

It is also known that our culture has led us to become accustomed to the conventional sitting position on a chair, and attempts to assume sitting positions on the ground are always accompanied by intense pain in the the knee and foot joints which prevent one enjoying the benefits of this position.

The technical problem which is therefore posed is that of providing a sitting device which allows natural alignment of the vertebrae of the vertebral column, the head, the chest and the pelvis, resulting in relaxing repositioning of all the parts of the body without needless muscular tension and offering the body a comfortable posture which alleviates the tension on the heels and the pressure of the weight acting on the shin and on the knees.

Within the scope of this problem a further requirement is to obtain relaxation of the body and in particular of the pit of the stomach, enabling the breath to emerge freely from the abdomen and allowing deeper breathing.

These technical problems are solved according to the present invention by a sitting device which comprises a support base, a support upright which is variable heightwise and inserted in the support base, and a sitting surface, the upper end of said upright having

engaging parts designed to co-operate with corresponding parts formed in the sitting surface so as to support said surface in such a way as to allow a variation in the angle of inclination thereof with respect to the resting surface of the base.

Further details may be obtained from the following description of a non-limiting example of embodiment of the invention with reference to the accompanying drawings, in which: Figure 1 shows a perspective, partially exploded view of the seat according to the invention; Figure 2 shows a section along a vertical plane of the seat according to Fig. 1; Figure 3a shows a partially sectioned view of an embodiment of the seat; Figure 3b shows a view of the seat according to Fig. 3a with the user sat on it; Figure 4a shows an external view of the seat according to Fig. 3a; Figure 4b shows a side view of the seat according to Fig. 4a with the user sat on it; Figure 5 shows a view of a variant of the part connecting support base and seat.

As can be seen from the Figures, the seat according to the invention is composed of a base 10 on which an upright 20 supporting the sitting surface 30 can be engaged.

More in particular, the base 10 comprises a part 11 resting on the ground and connected to an upper tapered part lla.

The base 10 is provided internally with an axial hole 12 in which there is formed a female thread 12a suitable for engagement with the threading 21a of a column 21 forming the upright 20.

The free upper end of said column 21 consists of an elongated body 22 having a cross-section of substantially triangular shape with the vertex 22a at the top. Said vertex is designed to be engaged with a corresponding seat 31 formed in the bottom surface of the sitting surface 30, in a substantially barycentric position. Said connection therefore keeps the sitting surface 30 in equilibrium on the column 21, but allows its inclination to be varied with respect to the direction of the axis of contact of the two parts and hence with respect to the base and the associated resting surface. The screw/female thread connection between the column 21 and the base 11 allows adjustment of the height of the sitting surface 30 from the ground in accordance with the characteristics of the user.

The sitting surface 30 has, in turn, a front part with curved and symmetrical sections 32, so as to allow the user a leg position which does not generate muscular tension and/or effort.

As illustrated in Fig. 3a, the upright column may also be formed by means of a substantially parallepipedal, cylindrical or similar shaped element 121 inserted in a corresponding seat 112 of the base 10 and with an upper end 22 having a shape and cross-section similar to those described with reference to Fig. 1 and therefore suitable for supporting the sitting surface

30. Said element 121 is interchangeable and may have different heights or parts which allow variation in the height, so as to obtain the most suitable distance of the sitting surface 30 from the ground.

Figures 3b,4a,4b illustrate the different positions of the sitting surface and the user who may assume a seated position with the sitting surface horizontal (Fig. 3b) or seated position with the surface inclined (Fig. 4b).

Figure 5 illustrates finally a further embodiment of the seat according to the invention, in which the connection between column 21 and sitting surface 30 is obtained by means of a spherical surface 122 integral with the column 21 and a corresponding spherical seat 131 formed in the thickness of the sitting surface 30.

In this case the sitting surface is free to oscillate in any direction and is particularly suitable for allowing the user to assume inclined positions with respect to the vertical.

In all the versions it is envisaged that the base 10 has, formed in it, gripping elements such as recesses 13 or the like.

It is therefore obvious how the seat according to the invention allows the user to assume seated positions resulting in balanced distribution of the weight of the upper trunk on the buttocks, while maintaining the function of supporting the lower part of the back, and natural alignment of the vertebrae of the vertebral column, the head, the trunk and the pelvis, allowing relaxing repositioning of all the parts of the body without needless muscular tension and offering the body a comfortable posture which alleviates the tension on the heels and the pressure of the weight acting on the shin and on the knees.

In particular the seated user has the possibility of sitting with the feet underneath the buttocks and the big toes in contact or at a distance depending on requirements, as in the "seiza" position, or with the legs crossed, as in the "lotus" position.