Configuration of a running surface for a manual treadmill

1. A manually powered treadmill, comprising:

a frame;

a front shaft coupled to the frame;

a rear shaft coupled to the frame; and

a running belt disposed about the front and rear shafts, wherein the running belt assumes at least a portion of a curved running surface, the curved running surface having a radius of curvature in a range of approximately 88 to 138 inches;

a bearing assembly at least partially supporting one of the front shaft or the rear shaft; and

a member coupled to the frame, wherein movement of the member results in rotational movement of the bearing assembly and the one of the front shaft or the rear shaft along a curve to alter a tension applied to the running belt.

2. The manually powered treadmill of claim 1 , wherein the radius of curvature is in a range of approximately 88 to 120 inches.

3. The manually powered treadmill of claim 1 , wherein the radius of curvature is approximately 90 inches.

4. The manually powered treadmill of claim 1 , further comprising:

a first plurality of bearings coupled to the frame on a first side of the frame and at least partially supporting the running belt; and

a second plurality of bearings coupled to the frame on a second side of the frame and at least partially supporting the running belt;

wherein the first plurality of bearings defines a first top profile and the second plurality of bearings defines a second top profile, wherein each of the first and second top profiles has the radius of curvature in the range of approximately 88 to 138 inches.

5. The manually powered treadmill of claim 4 , further comprising:

a pair of front running belt pulleys coupled to the front shaft and at least partially supporting the running belt; and

a pair of rear running belt pulleys coupled to the rear shaft and at least partially supporting the running belt;

wherein each pair of the front and rear running belt pulleys are respectively positioned slightly non-tangential to the first and second top profiles of the first and second pluralities of bearings.

6. The manually powered treadmill of claim 4 , wherein at least some of the first and second pluralities of bearings rotate as the running belt is rotated.

7. The manually powered treadmill of claim 1 , wherein at least one bearing in the first bearing assembly is a low-resistance bearing that utilizes a low viscosity bearing fluid.

8. The manually powered treadmill of claim 7 , wherein the low viscosity bearing fluid is low viscosity grease that has a National Lubricating Grease Institute classification of between 000 and 1.

9. A manual powered treadmill, comprising:

a frame;

a front shaft coupled to the frame;

a plurality of bearings coupled to the frame and defining a top profile;

a front running belt pulley coupled to the front shaft and having a first non-tangential relationship with the top profile; and

a running belt at least partially supported by the plurality of bearings and the front running belt pulley, the running belt defining a curved running surface having a radius of curvature in a range of approximately 88 to 138 inches;

a bearing assembly at least partially supporting the front shaft; and

a member coupled to the frame, wherein movement of the member results in rotational movement of the bearing assembly and the front shaft along a curve towards or away from the front end of the frame to alter a tension applied to the running belt.

10. The manually powered treadmill of claim 9 , wherein the front running belt pulley is positioned slightly above the top profile to create the first non-tangential relationship with the top profile.

11. The manually powered treadmill of claim 10 , wherein the first non-tangential relationship facilitates maintenance of the curved running surface.

12. The manually powered treadmill of claim 9 , further comprising:

a rear shaft coupled to the frame and disposed longitudinally opposite the front shaft; and

a rear running belt pulley coupled to the rear shaft and at least partially supporting the running belt.

13. The manually powered treadmill of claim 12 , wherein the rear running belt pulley is positioned slightly below the top profile such that the rear running belt pulley has a second non-tangential relationship with the top profile.

14. The manually powered treadmill of claim 13 , wherein the front running belt pulley is positioned slightly above the top profile to create the first non-tangential relationship with the top profile, and wherein the first and second non-tangential relationships between the front and rear running belt pulleys and the top profile, respectively, facilitates maintenance of the curved running surface.

15. The manually powered treadmill of claim 14 , wherein a gap is defined between the front running belt pulley and a first end of the plurality of bearings, and wherein the rear running belt pulley is disposed at least partly underneath a second end of the plurality of bearings.

16. A treadmill, comprising:

a frame having a front end and a rear end, the front end disposed substantially longitudinally opposite the rear end;

a first bearing assembly coupling a front shaft to the frame near the front end, the first bearing assembly including a low-resistance bearing that utilizes a low viscosity bearing fluid;

a rear shaft coupled to the frame near the rear end; and

a running belt disposed about the front and rear shafts, wherein the running belt defines a curved running surface having a radius of curvature in a range of approximately 88 to 138 inches; and

a first tension assembly coupled to the frame and configured to adjust a position of the front shaft relative to the rear shaft to adjust a tension of the running belt, the first tension assembly including a movable rod coupled to the frame, wherein movement of the movable rod results in rotational movement of the first bearing assembly along a curve towards or away from the front end of the frame to alter the tension applied to the running belt.

17. The treadmill of claim 16 , wherein the first tension assembly includes:

a block coupled to the frame; and

wherein the movable rod is threadedly engageable with the block, such that rotational movement of the movable rod relative to the block moves the movable rod closer to or further from the first bearing assembly.

18. The treadmill of claim 16 , wherein the low viscosity bearing fluid is low viscosity grease that has a National Lubricating Grease Institute classification of between 000 and 1.

19. The treadmill of claim 16 , wherein the radius of curvature is in a range of approximately 88 to 120 inches.