Load support structure

1. A body support structure comprising:

a frame defining a backrest, the backrest having an upper section and a lower section; and

a membrane attached to the frame and comprising intertwined filaments, the membrane having a first region with a first stiffness, a second region with a second stiffness, and a third region with a third stiffness,

wherein the second stiffness is greater than the first stiffness and the third stiffness is greater than the first stiffness and the second stiffness, and

wherein the first region is positioned in the lower section of the backrest and at least a portion of the first region is configured to support the lower back of a user, the third region is positioned above the first region and at least a portion of the third region is configured to support the spine of a user, and the second region is positioned above the first region.

2. The body support structure of claim 1 wherein the second region includes a lumbar region of the backrest.

3. The body support structure of claim 1 wherein the second region includes an upper region of the backrest.

4. The body support structure of claim 1 wherein the membrane comprises monofilaments interwoven with multifilament yarn, and the different stiffnesses are formed by varying the flexural modulus of the monofilaments.

5. The body support structure of claim 1 wherein the frame comprises spaced apart frame sections defining an opening, and wherein the membrane is stretched and secured to the frame sections.

6. The body support structure of claim 1 wherein the third region includes a centrally-located, longitudinally-extending spinal region.

7. The body support structure of claim 1 wherein the third stiffness is about two times as stiff as the first stiffness and the second stiffness is about 1.5 times as stiff as the first stiffness.

8. The body support structure of claim 1 wherein the first and second regions have different quantities of filaments per inch.

9. A body support structure comprising:

a frame defining a seat, the seat having a front section and a rear section; and

a membrane attached to the frame and comprising intertwined filaments, the membrane having a first region with a first stiffness, a second region with a second stiffness, and a third region with a third stiffness,

wherein the second stiffness is greater than the first stiffness and the third stiffness is greater than the first stiffness and the second stiffness, and

wherein the third region is positioned in the front section of the seat, the second region is positioned behind and adjacent to the third region, and the first region is positioned behind and adjacent to the second region.

10. The body support structure of claim 9 wherein the frame comprises spaced apart frame sections defining an opening, wherein the membrane is secured to the frame sections and is suspended over the opening.

11. The body support structure of claim 9 wherein the third stiffness is about two times as stiff as the first stiffness and the second stiffness is about 1.5 times as stiff as the first stiffness.

12. The body support structure of claim 9 wherein the different stiffnesses are formed by varying the flexural modulus of the monofilaments.

13. The body support structure of claim 9 wherein the second region is contiguous with the first region and the third region.

14. The body support structure of claim 9 wherein the first and second regions have different quantities of elastomeric filaments per inch.

15. A body support structure comprising:

a frame; and

a membrane attached to the frame and comprising filaments, the membrane formed from a woven material having a first region with a first stiffness, a second region with a second stiffness, and a third region with a third stiffness,

wherein the second stiffness is greater than the first stiffness and the third stiffness is greater than the first stiffness and the second stiffness, and

wherein the first stiffness, second stiffness, and third stiffness are formed by variations in the membrane weave or material prior to attaching the membrane to the frame.

16. The body support structure of claim 15 wherein the third stiffness is about two times as stiff as the first stiffness and the second stiffness is about 1.5 times as stiff as the first stiffness.

17. The body support structure of claim 15 wherein the membrane includes elastomeric monofilaments interwoven with multifilament yarn, and the different stiffnesses are formed by varying the flexural modulus of the monofilaments.

18. The body support structure of claim 15 wherein the second region is contiguous with the first region and the third region.

19. The body support structure of claim 15 wherein the first and second regions have different quantities of elastomeric filaments per inch.

20. The body support structure of claim 15 wherein the frame defines a backrest, and wherein the first region is positioned in the lower section of the backrest and at least a portion of the first region is configured to support the lower back of a user, the third region is positioned above the first region and at least a portion of the third region is configured to support the spine of a user, and the second region is positioned above the first region.

21. The body support structure of claim 20 , wherein the frame further defines a seat having a front section and a rear section, wherein the membrane includes a fourth region with a fourth stiffness, a fifth region with a fifth stiffness, and a sixth region with a sixth stiffness, wherein the fifth stiffness is greater than the fourth stiffness and the sixth stiffness is greater than the fourth stiffness and the fifth stiffness, and wherein the sixth region is positioned in the front section of the seat, the fifth region is positioned behind and adjacent to the sixth region, and the fourth region is positioned behind and adjacent to the fifth region.